[PATCH v5] x86: load FPU registers on return to userland

[PATCH v5] x86: load FPU registers on return to userland

[Sebastian Andrzej Siewior]

This is a refurbished series originally started by by Rik van Riel. The
goal is load the FPU registers on return to userland and not on every
context switch. By this optimisation we can:
- avoid loading the registers if the task stays in kernel and does
  not return to userland
- make kernel_fpu_begin() cheaper: it only saves the registers on the
  first invocation. The second invocation does not need save them again.

To access the FPU registers in kernel we need:
- disable preemption to avoid that the scheduler switches tasks. By
  doing so it would set TIF_NEED_FPU_LOAD and the FPU registers would be
  not valid.
- disable BH because the softirq might use kernel_fpu_begin() and then
  set TIF_NEED_FPU_LOAD instead loading the FPU registers on completion.

v4…v5:
Rebased on top of a fix, noticed a problem with XSAVES and then redid
the restore on sig return (patch #26 to #28).

I don't like very much the sig save+restore thing that we are doing. It
has been always like that. I *think* that this is just because we have
nowhere to stash the FPU state while we are handling the signal. We
could add another fpu->state for the signal handler and avoid the thing.
Debian code-search revealed that `criu' is using it (and I didn't
figure out why). Nothing else (that is packaged in Debian). Maybe we
could get rid of this and if `criu' would then use a dedicated interface
for its needs rather the signal interface that happen to do what it
wants :)

v3…v4:
It has been suggested to remove the `initialized' member of the struct
fpu because it should not required be needed with lazy-FPU-restore and
would make the review easier. This is the first part of the series, the
second is basically the rebase of the v3 queue. As a result, the
diffstat became negative (which wasn't the case in previous version) :)
I tried to incorporate all the review comments that came up, some of
them were "outdated" after the removal of the `initialized' member. I'm
sorry should I missed any.

v1…v3:
v2 was never posted. I followed the idea to completely decouple PKRU
from xstate. This didn't quite work and made a few things complicated. 
One obvious required fixup is copy_fpstate_to_sigframe() where the PKRU
state needs to be fiddled into xstate. This required another
xfeatures_mask so that the sanity checks were performed and
xstate_offsets would be computed. Additionally ptrace also reads/sets
xstate in order to get/set the register and PKRU is one of them. So this
would need some fiddle, too.
In v3 I dropped that decouple idea. I also learned that the wrpkru
instruction is not privileged and so caching it in kernel does not work.
Instead I keep PKRU in xstate area and load it at context switch time
while the remaining registers are deferred (until return to userland).
The offset of PKRU within xstate is enumerated at boot time so why not
use it.

Rik van Riel (5):
  x86/fpu: Add (__)make_fpregs_active helpers
  x86/fpu: Eager switch PKRU state
  x86/fpu: Always store the registers in copy_fpstate_to_sigframe()
  x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD
  x86/fpu: Defer FPU state load until return to userspace

Sebastian Andrzej Siewior (24):
  x86/fpu: Use ULL for shift in xfeature_uncompacted_offset()
  x86/entry/32: Remove asm/math_emu.h include
  x86/entry: Remove _TIF_ALLWORK_MASK
  x86/pkeys: Make init_pkru_value static
  x86/fpu: add might_fault() to user_insn()
  x86/fpu: Update comment for __raw_xsave_addr()
  x86/fpu: don't export __kernel_fpu_{begin|end}()
  x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig()
  x86/fpu: Remove fpu__restore()
  x86/fpu: Remove preempt_disable() in fpu__clear()
  x86/fpu: Always init the `state' in fpu__clear()
  x86/fpu: Remove fpu->initialized usage in copy_fpstate_to_sigframe()
  x86/fpu: Don't save fxregs for ia32 frames in
    copy_fpstate_to_sigframe()
  x86/fpu: Remove fpu->initialized
  x86/fpu: Remove user_fpu_begin()
  x86/fpu: Make __raw_xsave_addr() use feature number instead of mask
  x86/fpu: Make get_xsave_field_ptr() and get_xsave_addr() use feature
    number instead of mask
  x86/fpu: Only write PKRU if it is different from current
  x86/pkeys: Don't check if PKRU is zero before writting it
  x86/entry: Add TIF_NEED_FPU_LOAD
  x86/fpu: Update xstate's PKRU value on write_pkru()
  x86/fpu: Inline copy_user_to_fpregs_zeroing()
  x86/fpu: Let __fpu__restore_sig() restore the !32bit+fxsr frame from
    kernel memory
  x86/fpu: Merge the two code paths in __fpu__restore_sig()

 Documentation/preempt-locking.txt    |   1 -
 arch/x86/entry/common.c              |   8 ++
 arch/x86/ia32/ia32_signal.c          |  17 +--
 arch/x86/include/asm/efi.h           |   6 +-
 arch/x86/include/asm/fpu/api.h       |  47 ++++--
 arch/x86/include/asm/fpu/internal.h  | 152 ++++++++------------
 arch/x86/include/asm/fpu/signal.h    |   2 +-
 arch/x86/include/asm/fpu/types.h     |   9 --
 arch/x86/include/asm/fpu/xstate.h    |   5 +-
 arch/x86/include/asm/pgtable.h       |  20 ++-
 arch/x86/include/asm/special_insns.h |  13 +-
 arch/x86/include/asm/thread_info.h   |  10 +-
 arch/x86/include/asm/trace/fpu.h     |   8 +-
 arch/x86/kernel/fpu/core.c           | 199 ++++++++++++--------------
 arch/x86/kernel/fpu/init.c           |   2 -
 arch/x86/kernel/fpu/regset.c         |  24 +---
 arch/x86/kernel/fpu/signal.c         | 206 ++++++++++++---------------
 arch/x86/kernel/fpu/xstate.c         |  47 +++---
 arch/x86/kernel/process.c            |   2 +-
 arch/x86/kernel/process_32.c         |  14 +-
 arch/x86/kernel/process_64.c         |  11 +-
 arch/x86/kernel/signal.c             |  17 +--
 arch/x86/kernel/traps.c              |   2 +-
 arch/x86/kvm/x86.c                   |  47 +++---
 arch/x86/math-emu/fpu_entry.c        |   3 -
 arch/x86/mm/mpx.c                    |   6 +-
 arch/x86/mm/pkeys.c                  |  15 +-
 27 files changed, 424 insertions(+), 469 deletions(-)

 git://git.kernel.org/pub/scm/linux/kernel/git/bigeasy/staging.git x86_fpu_rtu_v5

Sebastian

[PATCH 01/29] x86/fpu: Use ULL for shift in xfeature_uncompacted_offset()

[Sebastian Andrzej Siewior]

The xfeature mask is 64bit so a shift from a number to its mask should
have LL prefix or else nr > 31 will be lost. This is not a problem now
but should XFEATURE_MASK_SUPERVISOR gain a bit >31 then this check won't
catch it.

Use BIT_ULL() to compute a mask from a number.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/xstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 87a57b7642d36..69d5740ed2546 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -444,7 +444,7 @@ static int xfeature_uncompacted_offset(int xfeature_nr)
 	 * format. Checking a supervisor state's uncompacted offset is
 	 * an error.
 	 */
-	if (XFEATURE_MASK_SUPERVISOR & (1 << xfeature_nr)) {
+	if (XFEATURE_MASK_SUPERVISOR & BIT_ULL(xfeature_nr)) {
 		WARN_ONCE(1, "No fixed offset for xstate %d\n", xfeature_nr);
 		return -1;
 	}
-- 
2.20.0.rc1

Re: [PATCH 01/29] x86/fpu: Use ULL for shift in xfeature_uncompacted_offset()

[Rik van Riel]

[-- Attachment #1: Type: text/plain, Size: 518 bytes --]

On Wed, 2018-11-28 at 23:20 +0100, Sebastian Andrzej Siewior wrote:
> The xfeature mask is 64bit so a shift from a number to its mask
> should
> have LL prefix or else nr > 31 will be lost. This is not a problem
> now
> but should XFEATURE_MASK_SUPERVISOR gain a bit >31 then this check
> won't
> catch it.
> 
> Use BIT_ULL() to compute a mask from a number.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Rik van Riel <riel@surriel.com>

-- 
All Rights Reversed.

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[tip:x86/fpu] x86/fpu: Use unsigned long long shift in xfeature_uncompacted_offset()

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  d08452390179710dc7989242605e3c1faa62b64f
Gitweb:     https://git.kernel.org/tip/d08452390179710dc7989242605e3c1faa62b64f
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 28 Nov 2018 23:20:07 +0100
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Mon, 3 Dec 2018 18:40:28 +0100

x86/fpu: Use unsigned long long shift in xfeature_uncompacted_offset()

The xfeature mask is 64-bit so a shift from a number to its mask should
have ULL suffix or else bits above position 31 will be lost. This is not
a problem now but should XFEATURE_MASK_SUPERVISOR gain a bit >31 then
this check won't catch it.

Use BIT_ULL() to compute a mask from a number.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181128222035.2996-2-bigeasy@linutronix.de
---
 arch/x86/kernel/fpu/xstate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 87a57b7642d3..69d5740ed254 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -444,7 +444,7 @@ static int xfeature_uncompacted_offset(int xfeature_nr)
 	 * format. Checking a supervisor state's uncompacted offset is
 	 * an error.
 	 */
-	if (XFEATURE_MASK_SUPERVISOR & (1 << xfeature_nr)) {
+	if (XFEATURE_MASK_SUPERVISOR & BIT_ULL(xfeature_nr)) {
 		WARN_ONCE(1, "No fixed offset for xstate %d\n", xfeature_nr);
 		return -1;
 	}

[PATCH 02/29] x86/entry/32: Remove asm/math_emu.h include

[Sebastian Andrzej Siewior]

The math_emu.h header files contains the definition of struct
math_emu_info. It is not used in this file.

Remove asm/math_emu.h include.

Reviewed-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/process_32.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 5046a3c9dec2f..1bf5b5830e81a 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -44,9 +44,6 @@
 #include <asm/processor.h>
 #include <asm/fpu/internal.h>
 #include <asm/desc.h>
-#ifdef CONFIG_MATH_EMULATION
-#include <asm/math_emu.h>
-#endif
 
 #include <linux/err.h>
 
-- 
2.20.0.rc1

Re: [PATCH 02/29] x86/entry/32: Remove asm/math_emu.h include

[Rik van Riel]

[-- Attachment #1: Type: text/plain, Size: 418 bytes --]

On Wed, 2018-11-28 at 23:20 +0100, Sebastian Andrzej Siewior wrote:
> The math_emu.h header files contains the definition of struct
> math_emu_info. It is not used in this file.
> 
> Remove asm/math_emu.h include.
> 
> Reviewed-by: Andy Lutomirski <luto@kernel.org>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Rik van Riel <riel@surriel.com>

-- 
All Rights Reversed.

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[tip:x86/fpu] x86/process/32: Remove asm/math_emu.h include

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  e08e32119b944f519664451bfb342a25b4045ead
Gitweb:     https://git.kernel.org/tip/e08e32119b944f519664451bfb342a25b4045ead
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 28 Nov 2018 23:20:08 +0100
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Mon, 3 Dec 2018 18:51:16 +0100

x86/process/32: Remove asm/math_emu.h include

The math_emu.h header files contains the definition of struct
math_emu_info which is not used in this file.

Remove the asm/math_emu.h include.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181128222035.2996-3-bigeasy@linutronix.de
---
 arch/x86/kernel/process_32.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index d3e593eb189f..575654db463e 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -44,9 +44,6 @@
 #include <asm/processor.h>
 #include <asm/fpu/internal.h>
 #include <asm/desc.h>
-#ifdef CONFIG_MATH_EMULATION
-#include <asm/math_emu.h>
-#endif
 
 #include <linux/err.h>
 

[PATCH 03/29] x86/entry: Remove _TIF_ALLWORK_MASK

[Sebastian Andrzej Siewior]

There is no user of _TIF_ALLWORK_MASK since commit 21d375b6b34ff
("x86/entry/64: Remove the SYSCALL64 fast path").
Remove unused define _TIF_ALLWORK_MASK.

Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/thread_info.h | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 2ff2a30a264f4..cd6920674b905 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -136,14 +136,6 @@ struct thread_info {
 	 _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT |	\
 	 _TIF_NOHZ)
 
-/* work to do on any return to user space */
-#define _TIF_ALLWORK_MASK						\
-	(_TIF_SYSCALL_TRACE | _TIF_NOTIFY_RESUME | _TIF_SIGPENDING |	\
-	 _TIF_NEED_RESCHED | _TIF_SINGLESTEP | _TIF_SYSCALL_EMU |	\
-	 _TIF_SYSCALL_AUDIT | _TIF_USER_RETURN_NOTIFY | _TIF_UPROBE |	\
-	 _TIF_PATCH_PENDING | _TIF_NOHZ | _TIF_SYSCALL_TRACEPOINT |	\
-	 _TIF_FSCHECK)
-
 /* flags to check in __switch_to() */
 #define _TIF_WORK_CTXSW							\
 	(_TIF_IO_BITMAP|_TIF_NOCPUID|_TIF_NOTSC|_TIF_BLOCKSTEP|_TIF_SSBD)
-- 
2.20.0.rc1

Re: [PATCH 03/29] x86/entry: Remove _TIF_ALLWORK_MASK

[Rik van Riel]

[-- Attachment #1: Type: text/plain, Size: 427 bytes --]

On Wed, 2018-11-28 at 23:20 +0100, Sebastian Andrzej Siewior wrote:
> There is no user of _TIF_ALLWORK_MASK since commit 21d375b6b34ff
> ("x86/entry/64: Remove the SYSCALL64 fast path").
> Remove unused define _TIF_ALLWORK_MASK.
> 
> Reviewed-by: Borislav Petkov <bp@suse.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Rik van Riel <riel@surriel.com>

-- 
All Rights Reversed.

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[tip:x86/fpu] x86/thread_info: Remove _TIF_ALLWORK_MASK

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  d23650e06299e9b2d04e090ab8c625cdf24465bf
Gitweb:     https://git.kernel.org/tip/d23650e06299e9b2d04e090ab8c625cdf24465bf
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 28 Nov 2018 23:20:09 +0100
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Mon, 3 Dec 2018 19:00:28 +0100

x86/thread_info: Remove _TIF_ALLWORK_MASK

There is no user of _TIF_ALLWORK_MASK since commit

  21d375b6b34ff ("x86/entry/64: Remove the SYSCALL64 fast path").

Remove the unused define _TIF_ALLWORK_MASK.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181128222035.2996-4-bigeasy@linutronix.de
---
 arch/x86/include/asm/thread_info.h | 8 --------
 1 file changed, 8 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 82b73b75d67c..e0eccbcb8447 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -140,14 +140,6 @@ struct thread_info {
 	 _TIF_SECCOMP | _TIF_SYSCALL_TRACEPOINT |	\
 	 _TIF_NOHZ)
 
-/* work to do on any return to user space */
-#define _TIF_ALLWORK_MASK						\
-	(_TIF_SYSCALL_TRACE | _TIF_NOTIFY_RESUME | _TIF_SIGPENDING |	\
-	 _TIF_NEED_RESCHED | _TIF_SINGLESTEP | _TIF_SYSCALL_EMU |	\
-	 _TIF_SYSCALL_AUDIT | _TIF_USER_RETURN_NOTIFY | _TIF_UPROBE |	\
-	 _TIF_PATCH_PENDING | _TIF_NOHZ | _TIF_SYSCALL_TRACEPOINT |	\
-	 _TIF_FSCHECK)
-
 /* flags to check in __switch_to() */
 #define _TIF_WORK_CTXSW_BASE						\
 	(_TIF_IO_BITMAP|_TIF_NOCPUID|_TIF_NOTSC|_TIF_BLOCKSTEP|		\

[PATCH 04/29] x86/pkeys: Make init_pkru_value static

[Sebastian Andrzej Siewior]

The variable init_pkru_value isn't used outside of this file.
Make init_pkru_value static.

Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/mm/pkeys.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index 6e98e0a7c9231..047a77f6a10cb 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -131,6 +131,7 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey
  * in the process's lifetime will not accidentally get access
  * to data which is pkey-protected later on.
  */
+static
 u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) |
 		      PKRU_AD_KEY( 4) | PKRU_AD_KEY( 5) | PKRU_AD_KEY( 6) |
 		      PKRU_AD_KEY( 7) | PKRU_AD_KEY( 8) | PKRU_AD_KEY( 9) |
-- 
2.20.0.rc1

Re: [PATCH 04/29] x86/pkeys: Make init_pkru_value static

[Rik van Riel]

[-- Attachment #1: Type: text/plain, Size: 370 bytes --]

On Wed, 2018-11-28 at 23:20 +0100, Sebastian Andrzej Siewior wrote:
> The variable init_pkru_value isn't used outside of this file.
> Make init_pkru_value static.
> 
> Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Rik van Riel <riel@surriel.com>

-- 
All Rights Reversed.

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[tip:x86/fpu] x86/pkeys: Make init_pkru_value static

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  1a4226efaf808fe9079ea3b29919883008918297
Gitweb:     https://git.kernel.org/tip/1a4226efaf808fe9079ea3b29919883008918297
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 28 Nov 2018 23:20:10 +0100
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Mon, 3 Dec 2018 19:10:18 +0100

x86/pkeys: Make init_pkru_value static

The variable init_pkru_value isn't used outside of this file.
Make it static.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181128222035.2996-5-bigeasy@linutronix.de
---
 arch/x86/mm/pkeys.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index 6e98e0a7c923..047a77f6a10c 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -131,6 +131,7 @@ int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, int pkey
  * in the process's lifetime will not accidentally get access
  * to data which is pkey-protected later on.
  */
+static
 u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) |
 		      PKRU_AD_KEY( 4) | PKRU_AD_KEY( 5) | PKRU_AD_KEY( 6) |
 		      PKRU_AD_KEY( 7) | PKRU_AD_KEY( 8) | PKRU_AD_KEY( 9) |

[PATCH 05/29] x86/fpu: add might_fault() to user_insn()

[Sebastian Andrzej Siewior]

Every user of user_insn() passes an user memory pointer to this macro.

Add might_fault() to user_insn() so we can spot users which are using
this macro in sections where page faulting is not allowed.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/internal.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 69dcdf195b611..978a1633c0698 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -106,6 +106,7 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu);
 #define user_insn(insn, output, input...)				\
 ({									\
 	int err;							\
+	might_fault();							\
 	asm volatile(ASM_STAC "\n"					\
 		     "1:" #insn "\n\t"					\
 		     "2: " ASM_CLAC "\n"				\
-- 
2.20.0.rc1

Re: [PATCH 05/29] x86/fpu: add might_fault() to user_insn()

[Rik van Riel]

[-- Attachment #1: Type: text/plain, Size: 447 bytes --]

On Wed, 2018-11-28 at 23:20 +0100, Sebastian Andrzej Siewior wrote:
> Every user of user_insn() passes an user memory pointer to this
> macro.
> 
> Add might_fault() to user_insn() so we can spot users which are using
> this macro in sections where page faulting is not allowed.

Nice catch.

> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Rik van Riel <riel@surriel.com>

-- 
All Rights Reversed.

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[tip:x86/fpu] x86/fpu: Add might_fault() to user_insn()

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  6637401c35b2f327a35d27f44bda05e327f2f017
Gitweb:     https://git.kernel.org/tip/6637401c35b2f327a35d27f44bda05e327f2f017
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 28 Nov 2018 23:20:11 +0100
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Mon, 3 Dec 2018 19:15:32 +0100

x86/fpu: Add might_fault() to user_insn()

Every user of user_insn() passes an user memory pointer to this macro.

Add might_fault() to user_insn() so we can spot users which are using
this macro in sections where page faulting is not allowed.

 [ bp: Space it out to make it more visible. ]

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181128222035.2996-6-bigeasy@linutronix.de
---
 arch/x86/include/asm/fpu/internal.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 69dcdf195b61..fa2c93cb42a2 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -106,6 +106,9 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu);
 #define user_insn(insn, output, input...)				\
 ({									\
 	int err;							\
+									\
+	might_fault();							\
+									\
 	asm volatile(ASM_STAC "\n"					\
 		     "1:" #insn "\n\t"					\
 		     "2: " ASM_CLAC "\n"				\

[PATCH 06/29] x86/fpu: Update comment for __raw_xsave_addr()

[Sebastian Andrzej Siewior]

The comment above __raw_xsave_addr() claims that the function does not
work for compacted buffers and was introduced in commit
  b8b9b6ba9dec3("x86/fpu: Allow setting of XSAVE state")

In this commit, the function was factored out of get_xsave_addr() and
this function claims that it works with "standard format or compacted
format of xsave area". It accesses the "xstate_comp_offsets" variable
for the actual offset and it was introduced in commit
  7496d6458fe32 ("Define kernel API to get address of each state in xsave area")

Based on the code (back then and now):
- xstate_offsets holds the standard offset.
- if compacted mode is not supported then xstate_comp_offsets gets the
  xstate_offsets copied.
- if compacted mode is supported then xstate_comp_offsets will hold the
  offset for the compacted buffer.

Based on that the function works for compacted buffers as long as the
CPU supports it and this what we care about.

Remove the "Note:" which is not accurate.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/xstate.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 69d5740ed2546..359564beab5c3 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -808,8 +808,6 @@ void fpu__resume_cpu(void)
  * Given an xstate feature mask, calculate where in the xsave
  * buffer the state is.  Callers should ensure that the buffer
  * is valid.
- *
- * Note: does not work for compacted buffers.
  */
 void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
 {
-- 
2.20.0.rc1

Re: [PATCH 06/29] x86/fpu: Update comment for __raw_xsave_addr()

[Rik van Riel]

[-- Attachment #1: Type: text/plain, Size: 646 bytes --]

On Wed, 2018-11-28 at 23:20 +0100, Sebastian Andrzej Siewior wrote:
> The comment above __raw_xsave_addr() claims that the function does
> not
> work for compacted buffers and was introduced in commit
>   b8b9b6ba9dec3("x86/fpu: Allow setting of XSAVE state")

...

> Based on that the function works for compacted buffers as long as the
> CPU supports it and this what we care about.
> 
> Remove the "Note:" which is not accurate.
> 
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Rik van Riel <riel@surriel.com>

-- 
All Rights Reversed.

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[tip:x86/fpu] x86/fpu: Update comment for __raw_xsave_addr()

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  2f2fcc40a961ed04f0e130803fbaa868c2899310
Gitweb:     https://git.kernel.org/tip/2f2fcc40a961ed04f0e130803fbaa868c2899310
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Wed, 28 Nov 2018 23:20:12 +0100
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Mon, 3 Dec 2018 19:27:14 +0100

x86/fpu: Update comment for __raw_xsave_addr()

The comment above __raw_xsave_addr() claims that the function does not
work for compacted buffers and was introduced in:

  b8b9b6ba9dec3 ("x86/fpu: Allow setting of XSAVE state")

In this commit, the function was factored out of get_xsave_addr() and
this function claims that it works with "standard format or compacted
format of xsave area". It accesses the "xstate_comp_offsets" variable
for the actual offset and it was introduced in commit

  7496d6458fe32 ("Define kernel API to get address of each state in xsave area")

Based on the code (back then and now):
- xstate_offsets holds the standard offset.
- if compacted mode is not supported then xstate_comp_offsets gets the
  xstate_offsets copied.
- if compacted mode is supported then xstate_comp_offsets will hold the
  offset for the compacted buffer.

Based on that the function works for compacted buffers as long as the
CPU supports it and this what we care about.

Remove the "Note:" which is not accurate.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181128222035.2996-7-bigeasy@linutronix.de
---
 arch/x86/kernel/fpu/xstate.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 69d5740ed254..359564beab5c 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -808,8 +808,6 @@ void fpu__resume_cpu(void)
  * Given an xstate feature mask, calculate where in the xsave
  * buffer the state is.  Callers should ensure that the buffer
  * is valid.
- *
- * Note: does not work for compacted buffers.
  */
 void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
 {

[PATCH 07/29] x86/fpu: don't export __kernel_fpu_{begin|end}()

[Sebastian Andrzej Siewior]

There is one user using __kernel_fpu_begin() and before invoking it, it
invokes preempt_disable(). So it could invoke kernel_fpu_begin() right
away. The 32bit version of arch_efi_call_virt_setup() and
arch_efi_call_virt_teardown() does this already.

The comment above *kernel_fpu*() claims that before invoking
__kernel_fpu_begin() preemption should be disabled and that KVM is a
good example of doing it. Well, KVM doesn't do that since commit

  f775b13eedee2 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")

so it is not an example anymore.
With EFI gone as the last user of __kernel_fpu_{begin|end}(), it can be
made static and not exported anymore.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/efi.h     |  6 ++----
 arch/x86/include/asm/fpu/api.h | 16 ++++++----------
 arch/x86/kernel/fpu/core.c     |  6 ++----
 3 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index eea40d52ca785..45864898f7e50 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -82,8 +82,7 @@ struct efi_scratch {
 #define arch_efi_call_virt_setup()					\
 ({									\
 	efi_sync_low_kernel_mappings();					\
-	preempt_disable();						\
-	__kernel_fpu_begin();						\
+	kernel_fpu_begin();						\
 	firmware_restrict_branch_speculation_start();			\
 									\
 	if (!efi_enabled(EFI_OLD_MEMMAP))				\
@@ -99,8 +98,7 @@ struct efi_scratch {
 		efi_switch_mm(efi_scratch.prev_mm);			\
 									\
 	firmware_restrict_branch_speculation_end();			\
-	__kernel_fpu_end();						\
-	preempt_enable();						\
+	kernel_fpu_end();						\
 })
 
 extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index a9caac9d4a729..d6e094c282779 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -12,17 +12,13 @@
 #define _ASM_X86_FPU_API_H
 
 /*
- * Careful: __kernel_fpu_begin/end() must be called with preempt disabled
- * and they don't touch the preempt state on their own.
- * If you enable preemption after __kernel_fpu_begin(), preempt notifier
- * should call the __kernel_fpu_end() to prevent the kernel/user FPU
- * state from getting corrupted. KVM for example uses this model.
- *
- * All other cases use kernel_fpu_begin/end() which disable preemption
- * during kernel FPU usage.
+ * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
+ * disables preemption so be carefull if you intend to use it for long periods
+ * of time.
+ * If you intend to use the FPU in softirq you need to check first with
+ * irq_fpu_usable() if it is possible.
+ * Using the FPU in hardirq is not allowed.
  */
-extern void __kernel_fpu_begin(void);
-extern void __kernel_fpu_end(void);
 extern void kernel_fpu_begin(void);
 extern void kernel_fpu_end(void);
 extern bool irq_fpu_usable(void);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 2ea85b32421a0..2e5003fef51a9 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -93,7 +93,7 @@ bool irq_fpu_usable(void)
 }
 EXPORT_SYMBOL(irq_fpu_usable);
 
-void __kernel_fpu_begin(void)
+static void __kernel_fpu_begin(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -111,9 +111,8 @@ void __kernel_fpu_begin(void)
 		__cpu_invalidate_fpregs_state();
 	}
 }
-EXPORT_SYMBOL(__kernel_fpu_begin);
 
-void __kernel_fpu_end(void)
+static void __kernel_fpu_end(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -122,7 +121,6 @@ void __kernel_fpu_end(void)
 
 	kernel_fpu_enable();
 }
-EXPORT_SYMBOL(__kernel_fpu_end);
 
 void kernel_fpu_begin(void)
 {
-- 
2.20.0.rc1

Re: [PATCH 07/29] x86/fpu: don't export __kernel_fpu_{begin|end}()

[Rik van Riel]

[-- Attachment #1: Type: text/plain, Size: 414 bytes --]

On Wed, 2018-11-28 at 23:20 +0100, Sebastian Andrzej Siewior wrote:
> 
> + * Use kernel_fpu_begin/end() if you intend to use FPU in kernel
> context. It
> + * disables preemption so be carefull if you intend to use it for
> long periods

Just how careful do you want to be?

One l seems sufficient :)

Feel free to add my Reviewed-by: once that spelling
error is fixed :)

-- 
All Rights Reversed.

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[PATCH 07/29 v2] x86/fpu: don't export __kernel_fpu_{begin|end}()

[Sebastian Andrzej Siewior]

There is one user using __kernel_fpu_begin() and before invoking it, it
invokes preempt_disable(). So it could invoke kernel_fpu_begin() right
away. The 32bit version of arch_efi_call_virt_setup() and
arch_efi_call_virt_teardown() does this already.

The comment above *kernel_fpu*() claims that before invoking
__kernel_fpu_begin() preemption should be disabled and that KVM is a
good example of doing it. Well, KVM doesn't do that since commit

  f775b13eedee2 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")

so it is not an example anymore.
With EFI gone as the last user of __kernel_fpu_{begin|end}(), it can be
made static and not exported anymore.

Reviewed-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
v1…v2: `carefull' -> `careful'

 arch/x86/include/asm/efi.h     |  6 ++----
 arch/x86/include/asm/fpu/api.h | 16 ++++++----------
 arch/x86/kernel/fpu/core.c     |  6 ++----
 3 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index eea40d52ca785..45864898f7e50 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -82,8 +82,7 @@ struct efi_scratch {
 #define arch_efi_call_virt_setup()					\
 ({									\
 	efi_sync_low_kernel_mappings();					\
-	preempt_disable();						\
-	__kernel_fpu_begin();						\
+	kernel_fpu_begin();						\
 	firmware_restrict_branch_speculation_start();			\
 									\
 	if (!efi_enabled(EFI_OLD_MEMMAP))				\
@@ -99,8 +98,7 @@ struct efi_scratch {
 		efi_switch_mm(efi_scratch.prev_mm);			\
 									\
 	firmware_restrict_branch_speculation_end();			\
-	__kernel_fpu_end();						\
-	preempt_enable();						\
+	kernel_fpu_end();						\
 })
 
 extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index a9caac9d4a729..e368d8d94ca68 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -12,17 +12,13 @@
 #define _ASM_X86_FPU_API_H
 
 /*
- * Careful: __kernel_fpu_begin/end() must be called with preempt disabled
- * and they don't touch the preempt state on their own.
- * If you enable preemption after __kernel_fpu_begin(), preempt notifier
- * should call the __kernel_fpu_end() to prevent the kernel/user FPU
- * state from getting corrupted. KVM for example uses this model.
- *
- * All other cases use kernel_fpu_begin/end() which disable preemption
- * during kernel FPU usage.
+ * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
+ * disables preemption so be careful if you intend to use it for long periods
+ * of time.
+ * If you intend to use the FPU in softirq you need to check first with
+ * irq_fpu_usable() if it is possible.
+ * Using the FPU in hardirq is not allowed.
  */
-extern void __kernel_fpu_begin(void);
-extern void __kernel_fpu_end(void);
 extern void kernel_fpu_begin(void);
 extern void kernel_fpu_end(void);
 extern bool irq_fpu_usable(void);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 2ea85b32421a0..2e5003fef51a9 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -93,7 +93,7 @@ bool irq_fpu_usable(void)
 }
 EXPORT_SYMBOL(irq_fpu_usable);
 
-void __kernel_fpu_begin(void)
+static void __kernel_fpu_begin(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -111,9 +111,8 @@ void __kernel_fpu_begin(void)
 		__cpu_invalidate_fpregs_state();
 	}
 }
-EXPORT_SYMBOL(__kernel_fpu_begin);
 
-void __kernel_fpu_end(void)
+static void __kernel_fpu_end(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -122,7 +121,6 @@ void __kernel_fpu_end(void)
 
 	kernel_fpu_enable();
 }
-EXPORT_SYMBOL(__kernel_fpu_end);
 
 void kernel_fpu_begin(void)
 {
-- 
2.20.0.rc1

[tip:x86/fpu] x86/fpu: Don't export __kernel_fpu_{begin,end}()

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  7d79adb87fa79e4a4c59424fd5b5a922861fc5f6
Gitweb:     https://git.kernel.org/tip/7d79adb87fa79e4a4c59424fd5b5a922861fc5f6
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Thu, 29 Nov 2018 16:02:10 +0100
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Mon, 3 Dec 2018 19:37:27 +0100

x86/fpu: Don't export __kernel_fpu_{begin,end}()

There is one user of __kernel_fpu_begin() and before invoking it,
it invokes preempt_disable(). So it could invoke kernel_fpu_begin()
right away. The 32bit version of arch_efi_call_virt_setup() and
arch_efi_call_virt_teardown() does this already.

The comment above *kernel_fpu*() claims that before invoking
__kernel_fpu_begin() preemption should be disabled and that KVM is a
good example of doing it. Well, KVM doesn't do that since commit

  f775b13eedee2 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")

so it is not an example anymore.

With EFI gone as the last user of __kernel_fpu_{begin|end}(), both can
be made static and not exported anymore.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: linux-efi <linux-efi@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@linutronix.de
---
 arch/x86/include/asm/efi.h     |  6 ++----
 arch/x86/include/asm/fpu/api.h | 16 ++++++----------
 arch/x86/kernel/fpu/core.c     |  6 ++----
 3 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index eea40d52ca78..45864898f7e5 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -82,8 +82,7 @@ struct efi_scratch {
 #define arch_efi_call_virt_setup()					\
 ({									\
 	efi_sync_low_kernel_mappings();					\
-	preempt_disable();						\
-	__kernel_fpu_begin();						\
+	kernel_fpu_begin();						\
 	firmware_restrict_branch_speculation_start();			\
 									\
 	if (!efi_enabled(EFI_OLD_MEMMAP))				\
@@ -99,8 +98,7 @@ struct efi_scratch {
 		efi_switch_mm(efi_scratch.prev_mm);			\
 									\
 	firmware_restrict_branch_speculation_end();			\
-	__kernel_fpu_end();						\
-	preempt_enable();						\
+	kernel_fpu_end();						\
 })
 
 extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index a9caac9d4a72..e368d8d94ca6 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -12,17 +12,13 @@
 #define _ASM_X86_FPU_API_H
 
 /*
- * Careful: __kernel_fpu_begin/end() must be called with preempt disabled
- * and they don't touch the preempt state on their own.
- * If you enable preemption after __kernel_fpu_begin(), preempt notifier
- * should call the __kernel_fpu_end() to prevent the kernel/user FPU
- * state from getting corrupted. KVM for example uses this model.
- *
- * All other cases use kernel_fpu_begin/end() which disable preemption
- * during kernel FPU usage.
+ * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
+ * disables preemption so be careful if you intend to use it for long periods
+ * of time.
+ * If you intend to use the FPU in softirq you need to check first with
+ * irq_fpu_usable() if it is possible.
+ * Using the FPU in hardirq is not allowed.
  */
-extern void __kernel_fpu_begin(void);
-extern void __kernel_fpu_end(void);
 extern void kernel_fpu_begin(void);
 extern void kernel_fpu_end(void);
 extern bool irq_fpu_usable(void);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 2ea85b32421a..2e5003fef51a 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -93,7 +93,7 @@ bool irq_fpu_usable(void)
 }
 EXPORT_SYMBOL(irq_fpu_usable);
 
-void __kernel_fpu_begin(void)
+static void __kernel_fpu_begin(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -111,9 +111,8 @@ void __kernel_fpu_begin(void)
 		__cpu_invalidate_fpregs_state();
 	}
 }
-EXPORT_SYMBOL(__kernel_fpu_begin);
 
-void __kernel_fpu_end(void)
+static void __kernel_fpu_end(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -122,7 +121,6 @@ void __kernel_fpu_end(void)
 
 	kernel_fpu_enable();
 }
-EXPORT_SYMBOL(__kernel_fpu_end);
 
 void kernel_fpu_begin(void)
 {

Re: [tip:x86/fpu] x86/fpu: Don't export __kernel_fpu_{begin,end}()

[Ard Biesheuvel]

On Mon, 3 Dec 2018 at 22:04, tip-bot for Sebastian Andrzej Siewior
<tipbot@zytor.com> wrote:
>
> Commit-ID:  7d79adb87fa79e4a4c59424fd5b5a922861fc5f6
> Gitweb:     https://git.kernel.org/tip/7d79adb87fa79e4a4c59424fd5b5a922861fc5f6
> Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> AuthorDate: Thu, 29 Nov 2018 16:02:10 +0100
> Committer:  Borislav Petkov <bp@suse.de>
> CommitDate: Mon, 3 Dec 2018 19:37:27 +0100
>
> x86/fpu: Don't export __kernel_fpu_{begin,end}()
>
> There is one user of __kernel_fpu_begin() and before invoking it,
> it invokes preempt_disable(). So it could invoke kernel_fpu_begin()
> right away. The 32bit version of arch_efi_call_virt_setup() and
> arch_efi_call_virt_teardown() does this already.
>
> The comment above *kernel_fpu*() claims that before invoking
> __kernel_fpu_begin() preemption should be disabled and that KVM is a
> good example of doing it. Well, KVM doesn't do that since commit
>
>   f775b13eedee2 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")
>
> so it is not an example anymore.
>
> With EFI gone as the last user of __kernel_fpu_{begin|end}(), both can
> be made static and not exported anymore.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Signed-off-by: Borislav Petkov <bp@suse.de>
> Reviewed-by: Rik van Riel <riel@surriel.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Nicolai Stange <nstange@suse.de>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: kvm ML <kvm@vger.kernel.org>
> Cc: linux-efi <linux-efi@vger.kernel.org>
> Cc: x86-ml <x86@kernel.org>
> Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@linutronix.de
> ---
>  arch/x86/include/asm/efi.h     |  6 ++----
>  arch/x86/include/asm/fpu/api.h | 16 ++++++----------
>  arch/x86/kernel/fpu/core.c     |  6 ++----
>  3 files changed, 10 insertions(+), 18 deletions(-)
>
> diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
> index eea40d52ca78..45864898f7e5 100644
> --- a/arch/x86/include/asm/efi.h
> +++ b/arch/x86/include/asm/efi.h
> @@ -82,8 +82,7 @@ struct efi_scratch {
>  #define arch_efi_call_virt_setup()                                     \
>  ({                                                                     \
>         efi_sync_low_kernel_mappings();                                 \
> -       preempt_disable();                                              \
> -       __kernel_fpu_begin();                                           \
> +       kernel_fpu_begin();                                             \
>         firmware_restrict_branch_speculation_start();                   \
>                                                                         \
>         if (!efi_enabled(EFI_OLD_MEMMAP))                               \
> @@ -99,8 +98,7 @@ struct efi_scratch {
>                 efi_switch_mm(efi_scratch.prev_mm);                     \
>                                                                         \
>         firmware_restrict_branch_speculation_end();                     \
> -       __kernel_fpu_end();                                             \
> -       preempt_enable();                                               \
> +       kernel_fpu_end();                                               \
>  })
>
>  extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,
> diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
> index a9caac9d4a72..e368d8d94ca6 100644
> --- a/arch/x86/include/asm/fpu/api.h
> +++ b/arch/x86/include/asm/fpu/api.h
> @@ -12,17 +12,13 @@
>  #define _ASM_X86_FPU_API_H
>
>  /*
> - * Careful: __kernel_fpu_begin/end() must be called with preempt disabled
> - * and they don't touch the preempt state on their own.
> - * If you enable preemption after __kernel_fpu_begin(), preempt notifier
> - * should call the __kernel_fpu_end() to prevent the kernel/user FPU
> - * state from getting corrupted. KVM for example uses this model.
> - *
> - * All other cases use kernel_fpu_begin/end() which disable preemption
> - * during kernel FPU usage.
> + * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
> + * disables preemption so be careful if you intend to use it for long periods
> + * of time.
> + * If you intend to use the FPU in softirq you need to check first with
> + * irq_fpu_usable() if it is possible.
> + * Using the FPU in hardirq is not allowed.

According to the documentation in x86/kernel/fpu/core.c, this is not
true. So which one is accurate?

>   */
> -extern void __kernel_fpu_begin(void);
> -extern void __kernel_fpu_end(void);
>  extern void kernel_fpu_begin(void);
>  extern void kernel_fpu_end(void);
>  extern bool irq_fpu_usable(void);
> diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
> index 2ea85b32421a..2e5003fef51a 100644
> --- a/arch/x86/kernel/fpu/core.c
> +++ b/arch/x86/kernel/fpu/core.c
> @@ -93,7 +93,7 @@ bool irq_fpu_usable(void)
>  }
>  EXPORT_SYMBOL(irq_fpu_usable);
>
> -void __kernel_fpu_begin(void)
> +static void __kernel_fpu_begin(void)
>  {
>         struct fpu *fpu = &current->thread.fpu;
>
> @@ -111,9 +111,8 @@ void __kernel_fpu_begin(void)
>                 __cpu_invalidate_fpregs_state();
>         }
>  }
> -EXPORT_SYMBOL(__kernel_fpu_begin);
>
> -void __kernel_fpu_end(void)
> +static void __kernel_fpu_end(void)
>  {
>         struct fpu *fpu = &current->thread.fpu;
>
> @@ -122,7 +121,6 @@ void __kernel_fpu_end(void)
>
>         kernel_fpu_enable();
>  }
> -EXPORT_SYMBOL(__kernel_fpu_end);
>
>  void kernel_fpu_begin(void)
>  {

Re: [tip:x86/fpu] x86/fpu: Don't export __kernel_fpu_{begin,end}()

[Borislav Petkov]

On Mon, Dec 03, 2018 at 10:12:19PM +0100, Ard Biesheuvel wrote:
> > + * Using the FPU in hardirq is not allowed.
> 
> According to the documentation in x86/kernel/fpu/core.c, this is not
> true. So which one is accurate?

I think you mean the irq from user mode... Yap, we do allow that.

Sebastian?

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [tip:x86/fpu] x86/fpu: Don't export __kernel_fpu_{begin,end}()

[Borislav Petkov]

On Mon, Dec 03, 2018 at 11:08:41PM +0100, Borislav Petkov wrote:
> On Mon, Dec 03, 2018 at 10:12:19PM +0100, Ard Biesheuvel wrote:
> > > + * Using the FPU in hardirq is not allowed.
> > 
> > According to the documentation in x86/kernel/fpu/core.c, this is not
> > true. So which one is accurate?
> 
> I think you mean the irq from user mode... Yap, we do allow that.
> 
> Sebastian?

Ok, I've zapped that sentence from the comment until we clarify what
Sebastian meant.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [tip:x86/fpu] x86/fpu: Don't export __kernel_fpu_{begin,end}()

[Sebastian Andrzej Siewior]

On 2018-12-03 23:08:41 [+0100], Borislav Petkov wrote:
> On Mon, Dec 03, 2018 at 10:12:19PM +0100, Ard Biesheuvel wrote:
> > > + * Using the FPU in hardirq is not allowed.
> > 
> > According to the documentation in x86/kernel/fpu/core.c, this is not
> > true. So which one is accurate?
> 
> I think you mean the irq from user mode... Yap, we do allow that.
> 
> Sebastian?

Do you refer to
| *   - by IRQ context code to potentially use the FPU
| *     if it's unused.
  
? It is possible to use the FPU in IRQ context.
The FPU could be used in user-context surrounded by kernel_fpu_begin().
This only disables preemption so an IRQ could interrupt it. This IRQ
could then use the FPU or raise a SoftIRQ which would use it.
Therefore on x86 it is required to check with irq_fpu_usable() if the
FPU can be used. If the FPU can not be used, you have to implement
fallback code.

With the "restore FPU on return to userland" series we need to modify
the FPU in a few places. The softirq and preemption is disabled. I
didn't find any in-IRQ users.
Going forward I would like to remove the in-IRQ part and
irq_fpu_usable() and disable softirq as part of kernel_fpu_begin().

> Thx.

Sebastian

Re: [tip:x86/fpu] x86/fpu: Don't export __kernel_fpu_{begin,end}()

[Borislav Petkov]

On Tue, Dec 04, 2018 at 01:15:10PM +0100, Sebastian Andrzej Siewior wrote:
> Do you refer to
> | *   - by IRQ context code to potentially use the FPU
> | *     if it's unused.
>   
> ? It is possible to use the FPU in IRQ context.

I mean interrupted_user_mode() where we apparently can use the FPU when
handling an IRQ from user mode.

> The FPU could be used in user-context surrounded by kernel_fpu_begin().

Right, that.

> This only disables preemption so an IRQ could interrupt it. This IRQ
> could then use the FPU or raise a SoftIRQ which would use it.
> Therefore on x86 it is required to check with irq_fpu_usable() if the

Yes, and the check that thing does is:

        return !in_interrupt() ||
                interrupted_user_mode() || ...

so you're either *not* in interrupt, or you've gotten the IRQ while in
user mode.

> FPU can be used. If the FPU can not be used, you have to implement
> fallback code.
> 
> With the "restore FPU on return to userland" series we need to modify
> the FPU in a few places. The softirq and preemption is disabled. I
> didn't find any in-IRQ users.
> Going forward I would like to remove the in-IRQ part and
> irq_fpu_usable() and disable softirq as part of kernel_fpu_begin().

Right, and we should document all those new conditions prominently so
that people are aware.

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

[tip:x86/fpu] x86/fpu: Don't export __kernel_fpu_{begin,end}()

[tip-bot for Sebastian Andrzej Siewior]

Commit-ID:  12209993e98c5fa1855c467f22a24e3d5b8be205
Gitweb:     https://git.kernel.org/tip/12209993e98c5fa1855c467f22a24e3d5b8be205
Author:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
AuthorDate: Thu, 29 Nov 2018 16:02:10 +0100
Committer:  Borislav Petkov <bp@suse.de>
CommitDate: Tue, 4 Dec 2018 12:37:28 +0100

x86/fpu: Don't export __kernel_fpu_{begin,end}()

There is one user of __kernel_fpu_begin() and before invoking it,
it invokes preempt_disable(). So it could invoke kernel_fpu_begin()
right away. The 32bit version of arch_efi_call_virt_setup() and
arch_efi_call_virt_teardown() does this already.

The comment above *kernel_fpu*() claims that before invoking
__kernel_fpu_begin() preemption should be disabled and that KVM is a
good example of doing it. Well, KVM doesn't do that since commit

  f775b13eedee2 ("x86,kvm: move qemu/guest FPU switching out to vcpu_run")

so it is not an example anymore.

With EFI gone as the last user of __kernel_fpu_{begin|end}(), both can
be made static and not exported anymore.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Nicolai Stange <nstange@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Cc: linux-efi <linux-efi@vger.kernel.org>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20181129150210.2k4mawt37ow6c2vq@linutronix.de
---
 arch/x86/include/asm/efi.h     |  6 ++----
 arch/x86/include/asm/fpu/api.h | 15 +++++----------
 arch/x86/kernel/fpu/core.c     |  6 ++----
 3 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index eea40d52ca78..45864898f7e5 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -82,8 +82,7 @@ struct efi_scratch {
 #define arch_efi_call_virt_setup()					\
 ({									\
 	efi_sync_low_kernel_mappings();					\
-	preempt_disable();						\
-	__kernel_fpu_begin();						\
+	kernel_fpu_begin();						\
 	firmware_restrict_branch_speculation_start();			\
 									\
 	if (!efi_enabled(EFI_OLD_MEMMAP))				\
@@ -99,8 +98,7 @@ struct efi_scratch {
 		efi_switch_mm(efi_scratch.prev_mm);			\
 									\
 	firmware_restrict_branch_speculation_end();			\
-	__kernel_fpu_end();						\
-	preempt_enable();						\
+	kernel_fpu_end();						\
 })
 
 extern void __iomem *__init efi_ioremap(unsigned long addr, unsigned long size,
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index a9caac9d4a72..b56d504af654 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -12,17 +12,12 @@
 #define _ASM_X86_FPU_API_H
 
 /*
- * Careful: __kernel_fpu_begin/end() must be called with preempt disabled
- * and they don't touch the preempt state on their own.
- * If you enable preemption after __kernel_fpu_begin(), preempt notifier
- * should call the __kernel_fpu_end() to prevent the kernel/user FPU
- * state from getting corrupted. KVM for example uses this model.
- *
- * All other cases use kernel_fpu_begin/end() which disable preemption
- * during kernel FPU usage.
+ * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
+ * disables preemption so be careful if you intend to use it for long periods
+ * of time.
+ * If you intend to use the FPU in softirq you need to check first with
+ * irq_fpu_usable() if it is possible.
  */
-extern void __kernel_fpu_begin(void);
-extern void __kernel_fpu_end(void);
 extern void kernel_fpu_begin(void);
 extern void kernel_fpu_end(void);
 extern bool irq_fpu_usable(void);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 2ea85b32421a..2e5003fef51a 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -93,7 +93,7 @@ bool irq_fpu_usable(void)
 }
 EXPORT_SYMBOL(irq_fpu_usable);
 
-void __kernel_fpu_begin(void)
+static void __kernel_fpu_begin(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -111,9 +111,8 @@ void __kernel_fpu_begin(void)
 		__cpu_invalidate_fpregs_state();
 	}
 }
-EXPORT_SYMBOL(__kernel_fpu_begin);
 
-void __kernel_fpu_end(void)
+static void __kernel_fpu_end(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -122,7 +121,6 @@ void __kernel_fpu_end(void)
 
 	kernel_fpu_enable();
 }
-EXPORT_SYMBOL(__kernel_fpu_end);
 
 void kernel_fpu_begin(void)
 {

[PATCH 08/29] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig()

[Sebastian Andrzej Siewior]

This is a preparation for the removal of the ->initialized member in the
fpu struct.
__fpu__restore_sig() is deactivating the FPU via fpu__drop() and then
setting manually ->initialized followed by fpu__restore(). The result is
that it is possible to manipulate fpu->state and the state of registers
won't be saved/restored on a context switch which would overwrite
fpu->state.

Don't access the fpu->state while the content is read from user space
and examined / sanitized. Use a temporary kmalloc() buffer for the
preparation of the FPU registers and once the state is considered okay,
load it. Should something go wrong, return with an error and without
altering the original FPU registers.

The removal of "fpu__initialize()" is a nop because fpu->initialized is
already set for the user task.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/signal.h |  2 +-
 arch/x86/kernel/fpu/regset.c      |  5 ++--
 arch/x86/kernel/fpu/signal.c      | 41 ++++++++++++-------------------
 3 files changed, 19 insertions(+), 29 deletions(-)

diff --git a/arch/x86/include/asm/fpu/signal.h b/arch/x86/include/asm/fpu/signal.h
index 44bbc39a57b30..7fb516b6893a8 100644
--- a/arch/x86/include/asm/fpu/signal.h
+++ b/arch/x86/include/asm/fpu/signal.h
@@ -22,7 +22,7 @@ int ia32_setup_frame(int sig, struct ksignal *ksig,
 
 extern void convert_from_fxsr(struct user_i387_ia32_struct *env,
 			      struct task_struct *tsk);
-extern void convert_to_fxsr(struct task_struct *tsk,
+extern void convert_to_fxsr(struct fxregs_state *fxsave,
 			    const struct user_i387_ia32_struct *env);
 
 unsigned long
diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c
index bc02f5144b958..5dbc099178a88 100644
--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -269,11 +269,10 @@ convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk)
 		memcpy(&to[i], &from[i], sizeof(to[0]));
 }
 
-void convert_to_fxsr(struct task_struct *tsk,
+void convert_to_fxsr(struct fxregs_state *fxsave,
 		     const struct user_i387_ia32_struct *env)
 
 {
-	struct fxregs_state *fxsave = &tsk->thread.fpu.state.fxsave;
 	struct _fpreg *from = (struct _fpreg *) &env->st_space[0];
 	struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0];
 	int i;
@@ -350,7 +349,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1);
 	if (!ret)
-		convert_to_fxsr(target, &env);
+		convert_to_fxsr(&target->thread.fpu.state.fxsave, &env);
 
 	/*
 	 * update the header bit in the xsave header, indicating the
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index d99a8ee9e185e..9c35598697b94 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -207,11 +207,11 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 }
 
 static inline void
-sanitize_restored_xstate(struct task_struct *tsk,
+sanitize_restored_xstate(union fpregs_state *state,
 			 struct user_i387_ia32_struct *ia32_env,
 			 u64 xfeatures, int fx_only)
 {
-	struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
+	struct xregs_state *xsave = &state->xsave;
 	struct xstate_header *header = &xsave->header;
 
 	if (use_xsave()) {
@@ -238,7 +238,7 @@ sanitize_restored_xstate(struct task_struct *tsk,
 		 */
 		xsave->i387.mxcsr &= mxcsr_feature_mask;
 
-		convert_to_fxsr(tsk, ia32_env);
+		convert_to_fxsr(&state->fxsave, ia32_env);
 	}
 }
 
@@ -284,8 +284,6 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 	if (!access_ok(VERIFY_READ, buf, size))
 		return -EACCES;
 
-	fpu__initialize(fpu);
-
 	if (!static_cpu_has(X86_FEATURE_FPU))
 		return fpregs_soft_set(current, NULL,
 				       0, sizeof(struct user_i387_ia32_struct),
@@ -314,41 +312,34 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		 * thread's fpu state, reconstruct fxstate from the fsave
 		 * header. Validate and sanitize the copied state.
 		 */
+		union fpregs_state *state;
+		void *tmp;
 		struct user_i387_ia32_struct env;
 		int err = 0;
 
-		/*
-		 * Drop the current fpu which clears fpu->initialized. This ensures
-		 * that any context-switch during the copy of the new state,
-		 * avoids the intermediate state from getting restored/saved.
-		 * Thus avoiding the new restored state from getting corrupted.
-		 * We will be ready to restore/save the state only after
-		 * fpu->initialized is again set.
-		 */
-		fpu__drop(fpu);
+		tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
+		if (!tmp)
+			return -ENOMEM;
+		state = PTR_ALIGN(tmp, 64);
 
 		if (using_compacted_format()) {
-			err = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
+			err = copy_user_to_xstate(&state->xsave, buf_fx);
 		} else {
-			err = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
+			err = __copy_from_user(&state->xsave, buf_fx, state_size);
 
 			if (!err && state_size > offsetof(struct xregs_state, header))
-				err = validate_xstate_header(&fpu->state.xsave.header);
+				err = validate_xstate_header(&state->xsave.header);
 		}
 
 		if (err || __copy_from_user(&env, buf, sizeof(env))) {
-			fpstate_init(&fpu->state);
-			trace_x86_fpu_init_state(fpu);
 			err = -1;
 		} else {
-			sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
+			sanitize_restored_xstate(state, &env,
+						 xfeatures, fx_only);
+			copy_kernel_to_fpregs(state);
 		}
 
-		local_bh_disable();
-		fpu->initialized = 1;
-		fpu__restore(fpu);
-		local_bh_enable();
-
+		kfree(tmp);
 		return err;
 	} else {
 		/*
-- 
2.20.0.rc1

Re: [PATCH 08/29] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig()

[Borislav Petkov]

On Wed, Nov 28, 2018 at 11:20:14PM +0100, Sebastian Andrzej Siewior wrote:
> This is a preparation for the removal of the ->initialized member in the
> fpu struct.
> __fpu__restore_sig() is deactivating the FPU via fpu__drop() and then
> setting manually ->initialized followed by fpu__restore(). The result is
> that it is possible to manipulate fpu->state and the state of registers
> won't be saved/restored on a context switch which would overwrite
> fpu->state.
> 
> Don't access the fpu->state while the content is read from user space
> and examined / sanitized. Use a temporary kmalloc() buffer for the
> preparation of the FPU registers and once the state is considered okay,
> load it. Should something go wrong, return with an error and without
> altering the original FPU registers.
> 
> The removal of "fpu__initialize()" is a nop because fpu->initialized is
> already set for the user task.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  arch/x86/include/asm/fpu/signal.h |  2 +-
>  arch/x86/kernel/fpu/regset.c      |  5 ++--
>  arch/x86/kernel/fpu/signal.c      | 41 ++++++++++++-------------------
>  3 files changed, 19 insertions(+), 29 deletions(-)

...

> diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
> index d99a8ee9e185e..9c35598697b94 100644
> --- a/arch/x86/kernel/fpu/signal.c
> +++ b/arch/x86/kernel/fpu/signal.c
> @@ -207,11 +207,11 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
>  }
>  
>  static inline void
> -sanitize_restored_xstate(struct task_struct *tsk,
> +sanitize_restored_xstate(union fpregs_state *state,
>  			 struct user_i387_ia32_struct *ia32_env,
>  			 u64 xfeatures, int fx_only)
>  {
> -	struct xregs_state *xsave = &tsk->thread.fpu.state.xsave;
> +	struct xregs_state *xsave = &state->xsave;
>  	struct xstate_header *header = &xsave->header;
>  
>  	if (use_xsave()) {
> @@ -238,7 +238,7 @@ sanitize_restored_xstate(struct task_struct *tsk,
>  		 */
>  		xsave->i387.mxcsr &= mxcsr_feature_mask;
>  
> -		convert_to_fxsr(tsk, ia32_env);
> +		convert_to_fxsr(&state->fxsave, ia32_env);
>  	}
>  }
>  
> @@ -284,8 +284,6 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
>  	if (!access_ok(VERIFY_READ, buf, size))
>  		return -EACCES;
>  
> -	fpu__initialize(fpu);
> -
>  	if (!static_cpu_has(X86_FEATURE_FPU))
>  		return fpregs_soft_set(current, NULL,
>  				       0, sizeof(struct user_i387_ia32_struct),
> @@ -314,41 +312,34 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
>  		 * thread's fpu state, reconstruct fxstate from the fsave
>  		 * header. Validate and sanitize the copied state.
>  		 */
> +		union fpregs_state *state;
> +		void *tmp;
>  		struct user_i387_ia32_struct env;
>  		int err = 0;

Sort those in reverse xmas order pls.

Otherwise looks ok.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [PATCH 08/29] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig()

[Sebastian Andrzej Siewior]

On 2018-12-06 21:07:22 [+0100], Borislav Petkov wrote:
> > @@ -314,41 +312,34 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
> >  		 * thread's fpu state, reconstruct fxstate from the fsave
> >  		 * header. Validate and sanitize the copied state.
> >  		 */
> > +		union fpregs_state *state;
> > +		void *tmp;
> >  		struct user_i387_ia32_struct env;
> >  		int err = 0;
> 
> Sort those in reverse xmas order pls.
> 
> Otherwise looks ok.

You mean:
  		struct user_i387_ia32_struct env;
 +		union fpregs_state *state;
 +		void *tmp;
  		int err = 0;
?

Sebastian

Re: [PATCH 08/29] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig()

[Borislav Petkov]

On Fri, Dec 07, 2018 at 09:17:13AM +0100, Sebastian Andrzej Siewior wrote:
> You mean:
>   		struct user_i387_ia32_struct env;
>  +		union fpregs_state *state;
>  +		void *tmp;
>   		int err = 0;
> ?

Yap.

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

[PATCH 09/29] x86/fpu: Remove fpu__restore()

[Sebastian Andrzej Siewior]

There are no users of fpu__restore() so it is time to remove it.
The comment regarding fpu__restore() and TS bit is stale since commit
  b3b0870ef3ffe ("i387: do not preload FPU state at task switch time")
and has no meaning since.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 Documentation/preempt-locking.txt   |  1 -
 arch/x86/include/asm/fpu/internal.h |  1 -
 arch/x86/kernel/fpu/core.c          | 24 ------------------------
 arch/x86/kernel/process_32.c        |  4 +---
 arch/x86/kernel/process_64.c        |  4 +---
 5 files changed, 2 insertions(+), 32 deletions(-)

diff --git a/Documentation/preempt-locking.txt b/Documentation/preempt-locking.txt
index 509f5a422d571..dce336134e54a 100644
--- a/Documentation/preempt-locking.txt
+++ b/Documentation/preempt-locking.txt
@@ -52,7 +52,6 @@ preemption must be disabled around such regions.
 
 Note, some FPU functions are already explicitly preempt safe.  For example,
 kernel_fpu_begin and kernel_fpu_end will disable and enable preemption.
-However, fpu__restore() must be called with preemption disabled.
 
 
 RULE #3: Lock acquire and release must be performed by same task
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 978a1633c0698..415d43bdaaa76 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -28,7 +28,6 @@ extern void fpu__initialize(struct fpu *fpu);
 extern void fpu__prepare_read(struct fpu *fpu);
 extern void fpu__prepare_write(struct fpu *fpu);
 extern void fpu__save(struct fpu *fpu);
-extern void fpu__restore(struct fpu *fpu);
 extern int  fpu__restore_sig(void __user *buf, int ia32_frame);
 extern void fpu__drop(struct fpu *fpu);
 extern int  fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 2e5003fef51a9..1d3ae7988f7f2 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -303,30 +303,6 @@ void fpu__prepare_write(struct fpu *fpu)
 	}
 }
 
-/*
- * 'fpu__restore()' is called to copy FPU registers from
- * the FPU fpstate to the live hw registers and to activate
- * access to the hardware registers, so that FPU instructions
- * can be used afterwards.
- *
- * Must be called with kernel preemption disabled (for example
- * with local interrupts disabled, as it is in the case of
- * do_device_not_available()).
- */
-void fpu__restore(struct fpu *fpu)
-{
-	fpu__initialize(fpu);
-
-	/* Avoid __kernel_fpu_begin() right after fpregs_activate() */
-	kernel_fpu_disable();
-	trace_x86_fpu_before_restore(fpu);
-	fpregs_activate(fpu);
-	copy_kernel_to_fpregs(&fpu->state);
-	trace_x86_fpu_after_restore(fpu);
-	kernel_fpu_enable();
-}
-EXPORT_SYMBOL_GPL(fpu__restore);
-
 /*
  * Drops current FPU state: deactivates the fpregs and
  * the fpstate. NOTE: it still leaves previous contents
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 1bf5b5830e81a..b8a935adc96fc 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -271,9 +271,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	/*
 	 * Leave lazy mode, flushing any hypercalls made here.
 	 * This must be done before restoring TLS segments so
-	 * the GDT and LDT are properly updated, and must be
-	 * done before fpu__restore(), so the TS bit is up
-	 * to date.
+	 * the GDT and LDT are properly updated.
 	 */
 	arch_end_context_switch(next_p);
 
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 0e0b4288a4b2b..cf2c157714594 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -576,9 +576,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	/*
 	 * Leave lazy mode, flushing any hypercalls made here.  This
 	 * must be done after loading TLS entries in the GDT but before
-	 * loading segments that might reference them, and and it must
-	 * be done before fpu__restore(), so the TS bit is up to
-	 * date.
+	 * loading segments that might reference them.
 	 */
 	arch_end_context_switch(next_p);
 
-- 
2.20.0.rc1

[PATCH 10/29] x86/fpu: Remove preempt_disable() in fpu__clear()

[Sebastian Andrzej Siewior]

The preempt_disable() section was introduced in commit
  a10b6a16cdad8 ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic")
and it was said to be temporary.

fpu__initialize() initializes the FPU struct to its "init" value and
then sets ->initialized to 1. The last part is the important one.
The content of the `state' does not matter because it gets set via
copy_init_fpstate_to_fpregs().
A preemption here has little meaning because the register will always be
set to the same content after copy_init_fpstate_to_fpregs(). A softirq
with a kernel_fpu_begin() could also force to save FPU's register after
fpu__initialize() without changing the outcome here.

Remove the preempt_disable() section in fpu__clear(), preemption here
does not hurt.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/core.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 1d3ae7988f7f2..1940319268aef 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -366,11 +366,9 @@ void fpu__clear(struct fpu *fpu)
 	 * Make sure fpstate is cleared and initialized.
 	 */
 	if (static_cpu_has(X86_FEATURE_FPU)) {
-		preempt_disable();
 		fpu__initialize(fpu);
 		user_fpu_begin();
 		copy_init_fpstate_to_fpregs();
-		preempt_enable();
 	}
 }
 
-- 
2.20.0.rc1

[PATCH 11/29] x86/fpu: Always init the `state' in fpu__clear()

[Sebastian Andrzej Siewior]

fpu__clear() only initializes the `state' if the FPU is present. This
initialisation is also required for the FPU-less system and takes place
math_emulate(). Since fpu__initialize() only performs the initialization
if ->initialized is zero it does not matter that it is invoked each time
an opcode is emulated. It makes the removal of ->initialized easier if
the struct is also initialized in FPU-less case at the same time.

Move fpu__initialize() before the FPU check so it is also performed in
FPU-less case.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/internal.h | 1 -
 arch/x86/kernel/fpu/core.c          | 5 ++---
 arch/x86/math-emu/fpu_entry.c       | 3 ---
 3 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 415d43bdaaa76..1d0e043bfc447 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -24,7 +24,6 @@
 /*
  * High level FPU state handling functions:
  */
-extern void fpu__initialize(struct fpu *fpu);
 extern void fpu__prepare_read(struct fpu *fpu);
 extern void fpu__prepare_write(struct fpu *fpu);
 extern void fpu__save(struct fpu *fpu);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 1940319268aef..e43296854e379 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -223,7 +223,7 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
  * Activate the current task's in-memory FPU context,
  * if it has not been used before:
  */
-void fpu__initialize(struct fpu *fpu)
+static void fpu__initialize(struct fpu *fpu)
 {
 	WARN_ON_FPU(fpu != &current->thread.fpu);
 
@@ -236,7 +236,6 @@ void fpu__initialize(struct fpu *fpu)
 		fpu->initialized = 1;
 	}
 }
-EXPORT_SYMBOL_GPL(fpu__initialize);
 
 /*
  * This function must be called before we read a task's fpstate.
@@ -365,8 +364,8 @@ void fpu__clear(struct fpu *fpu)
 	/*
 	 * Make sure fpstate is cleared and initialized.
 	 */
+	fpu__initialize(fpu);
 	if (static_cpu_has(X86_FEATURE_FPU)) {
-		fpu__initialize(fpu);
 		user_fpu_begin();
 		copy_init_fpstate_to_fpregs();
 	}
diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
index 9e2ba7e667f61..a873da6b46d6b 100644
--- a/arch/x86/math-emu/fpu_entry.c
+++ b/arch/x86/math-emu/fpu_entry.c
@@ -113,9 +113,6 @@ void math_emulate(struct math_emu_info *info)
 	unsigned long code_base = 0;
 	unsigned long code_limit = 0;	/* Initialized to stop compiler warnings */
 	struct desc_struct code_descriptor;
-	struct fpu *fpu = &current->thread.fpu;
-
-	fpu__initialize(fpu);
 
 #ifdef RE_ENTRANT_CHECKING
 	if (emulating) {
-- 
2.20.0.rc1

Re: [PATCH 11/29] x86/fpu: Always init the `state' in fpu__clear()

[Borislav Petkov]

On Wed, Nov 28, 2018 at 11:20:17PM +0100, Sebastian Andrzej Siewior wrote:
> fpu__clear() only initializes the `state' if the FPU is present. This
> initialisation is also required for the FPU-less system and takes place
> math_emulate(). Since fpu__initialize() only performs the initialization
> if ->initialized is zero it does not matter that it is invoked each time
> an opcode is emulated. It makes the removal of ->initialized easier if
> the struct is also initialized in FPU-less case at the same time.
> 
> Move fpu__initialize() before the FPU check so it is also performed in
> FPU-less case.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  arch/x86/include/asm/fpu/internal.h | 1 -
>  arch/x86/kernel/fpu/core.c          | 5 ++---
>  arch/x86/math-emu/fpu_entry.c       | 3 ---
>  3 files changed, 2 insertions(+), 7 deletions(-)

...

> diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
> index 9e2ba7e667f61..a873da6b46d6b 100644
> --- a/arch/x86/math-emu/fpu_entry.c
> +++ b/arch/x86/math-emu/fpu_entry.c
> @@ -113,9 +113,6 @@ void math_emulate(struct math_emu_info *info)
>  	unsigned long code_base = 0;
>  	unsigned long code_limit = 0;	/* Initialized to stop compiler warnings */
>  	struct desc_struct code_descriptor;
> -	struct fpu *fpu = &current->thread.fpu;
> -
> -	fpu__initialize(fpu);

Ok, you're removing it here but where is the FPU going to be initialized
now in the FPU-less case?

IOW, it is not clear to me where fpu__clear() get called for the FPU
emulation case now...

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

Re: [PATCH 11/29] x86/fpu: Always init the `state' in fpu__clear()

[Sebastian Andrzej Siewior]

On 2018-12-12 18:11:29 [+0100], Borislav Petkov wrote:
> > diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
> > index 9e2ba7e667f61..a873da6b46d6b 100644
> > --- a/arch/x86/math-emu/fpu_entry.c
> > +++ b/arch/x86/math-emu/fpu_entry.c
> > @@ -113,9 +113,6 @@ void math_emulate(struct math_emu_info *info)
> >  	unsigned long code_base = 0;
> >  	unsigned long code_limit = 0;	/* Initialized to stop compiler warnings */
> >  	struct desc_struct code_descriptor;
> > -	struct fpu *fpu = &current->thread.fpu;
> > -
> > -	fpu__initialize(fpu);
> 
> Ok, you're removing it here but where is the FPU going to be initialized
> now in the FPU-less case?
> 
> IOW, it is not clear to me where fpu__clear() get called for the FPU
> emulation case now...

During fork() fpu__initialize() is called for both (with and without
FPU) systems. The difference is made in fpu__clear() where the init is
avoided in the FPU-less case. With this hunk:

--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -365,8 +364,8 @@ void fpu__clear(struct fpu *fpu)
        /*
         * Make sure fpstate is cleared and initialized.
         */
+       fpu__initialize(fpu);
        if (static_cpu_has(X86_FEATURE_FPU)) {
-               fpu__initialize(fpu);
                user_fpu_begin();
                copy_init_fpstate_to_fpregs();
        }                                                                                                                                                                                 
we have the initialization in both cases.
The only "negative" thing might be that we now have a memset(, 0, 684)
(fpstate_init_soft()) during fork which would be avoided in case the
FPU-less system has a userland which is compiled with a soft-FPU toolchain.

I would worry about it once someone complains (and I doubt someone
complains even if we remove soft FPU support).

Sebastian

[PATCH 12/29] x86/fpu: Remove fpu->initialized usage in copy_fpstate_to_sigframe()

[Sebastian Andrzej Siewior]

Since ->initialized is always true for user tasks and kernel threads
don't get this far, we always save the registers directly to userspace.

Remove check for ->initialized because it is always true and remove the
false condition.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/signal.c | 30 ++++++------------------------
 1 file changed, 6 insertions(+), 24 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 9c35598697b94..42e0f98f34f54 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -157,7 +157,6 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
 int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 {
 	struct fpu *fpu = &current->thread.fpu;
-	struct xregs_state *xsave = &fpu->state.xsave;
 	struct task_struct *tsk = current;
 	int ia32_fxstate = (buf != buf_fx);
 
@@ -172,29 +171,12 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 			sizeof(struct user_i387_ia32_struct), NULL,
 			(struct _fpstate_32 __user *) buf) ? -1 : 1;
 
-	if (fpu->initialized || using_compacted_format()) {
-		/* Save the live register state to the user directly. */
-		if (copy_fpregs_to_sigframe(buf_fx))
-			return -1;
-		/* Update the thread's fxstate to save the fsave header. */
-		if (ia32_fxstate)
-			copy_fxregs_to_kernel(fpu);
-	} else {
-		/*
-		 * It is a *bug* if kernel uses compacted-format for xsave
-		 * area and we copy it out directly to a signal frame. It
-		 * should have been handled above by saving the registers
-		 * directly.
-		 */
-		if (boot_cpu_has(X86_FEATURE_XSAVES)) {
-			WARN_ONCE(1, "x86/fpu: saving compacted-format xsave area to a signal frame!\n");
-			return -1;
-		}
-
-		fpstate_sanitize_xstate(fpu);
-		if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
-			return -1;
-	}
+	/* Save the live register state to the user directly. */
+	if (copy_fpregs_to_sigframe(buf_fx))
+		return -1;
+	/* Update the thread's fxstate to save the fsave header. */
+	if (ia32_fxstate)
+		copy_fxregs_to_kernel(fpu);
 
 	/* Save the fsave header for the 32-bit frames. */
 	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
-- 
2.20.0.rc1

[PATCH 13/29] x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe()

[Sebastian Andrzej Siewior]

Why does copy_fpstate_to_sigframe() do copy_fxregs_to_kernel() in the
ia32_fxstate case? I don't know. It just does.
Maybe it was required at some point, maybe it was added by accident and
nobody noticed it because it makes no difference.

In copy_fpstate_to_sigframe() we stash the FPU state into the task's
stackframe. Then the CPU's FPU registers (and its fpu->state) are
cleared (handle_signal() does fpu__clear()). So it makes *no* difference
what happens to fpu->state after copy_fpregs_to_sigframe().

Remove copy_fxregs_to_kernel() since it does not matter what it does and
save a few cycles.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/signal.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 42e0f98f34f54..3a59c578440e2 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -174,9 +174,6 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 	/* Save the live register state to the user directly. */
 	if (copy_fpregs_to_sigframe(buf_fx))
 		return -1;
-	/* Update the thread's fxstate to save the fsave header. */
-	if (ia32_fxstate)
-		copy_fxregs_to_kernel(fpu);
 
 	/* Save the fsave header for the 32-bit frames. */
 	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
-- 
2.20.0.rc1

[PATCH 14/29] x86/fpu: Remove fpu->initialized

[Sebastian Andrzej Siewior]

The `initialized' member of the fpu struct is always set to one user
tasks and zero for kernel tasks. This avoids saving/restoring the FPU
registers for kernel threads.

I expect that fpu->initialized is always 1 and the 0 case has been
removed or is not important. For instance fpu__drop() sets the value to
zero and its caller call either fpu__initialize() (which would
set it back to one) or don't return to userland.

The context switch code (switch_fpu_prepare() + switch_fpu_finish())
can't unconditionally save/restore registers for kernel threads. I have
no idea what will happen if we restore a zero FPU context for the kernel
thread (since it never was initialized). Also it has been agreed that
for PKRU we don't want a random state (inherited from the previous task)
but a deterministic one.

For kernel_fpu_begin() (+end) the situation is similar: The kernel test
bot told me, that EFI with runtime services uses this before
alternatives_patched is true. Which means that this function is used too
early and it wasn't the case before.

For those two cases current->mm is used to determine between user &
kernel thread. For kernel_fpu_begin() we skip save/restore of the FPU
registers.
During the context switch into a kernel thread we don't do anything.
There is no reason to save the FPU state of a kernel thread.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/ia32/ia32_signal.c         | 17 +++-----
 arch/x86/include/asm/fpu/internal.h | 15 +++----
 arch/x86/include/asm/fpu/types.h    |  9 ----
 arch/x86/include/asm/trace/fpu.h    |  5 +--
 arch/x86/kernel/fpu/core.c          | 68 ++++++++---------------------
 arch/x86/kernel/fpu/init.c          |  2 -
 arch/x86/kernel/fpu/regset.c        | 19 ++------
 arch/x86/kernel/fpu/xstate.c        |  2 -
 arch/x86/kernel/process_32.c        |  4 +-
 arch/x86/kernel/process_64.c        |  4 +-
 arch/x86/kernel/signal.c            | 17 +++-----
 arch/x86/mm/pkeys.c                 |  7 +--
 12 files changed, 49 insertions(+), 120 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 86b1341cba9ac..eb215ac5d9f46 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -216,8 +216,7 @@ static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
 				 size_t frame_size,
 				 void __user **fpstate)
 {
-	struct fpu *fpu = &current->thread.fpu;
-	unsigned long sp;
+	unsigned long sp, fx_aligned, math_size;
 
 	/* Default to using normal stack */
 	sp = regs->sp;
@@ -231,15 +230,11 @@ static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
 		 ksig->ka.sa.sa_restorer)
 		sp = (unsigned long) ksig->ka.sa.sa_restorer;
 
-	if (fpu->initialized) {
-		unsigned long fx_aligned, math_size;
-
-		sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
-		*fpstate = (struct _fpstate_32 __user *) sp;
-		if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
-				    math_size) < 0)
-			return (void __user *) -1L;
-	}
+	sp = fpu__alloc_mathframe(sp, 1, &fx_aligned, &math_size);
+	*fpstate = (struct _fpstate_32 __user *) sp;
+	if (copy_fpstate_to_sigframe(*fpstate, (void __user *)fx_aligned,
+				     math_size) < 0)
+		return (void __user *) -1L;
 
 	sp -= frame_size;
 	/* Align the stack pointer according to the i386 ABI,
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 1d0e043bfc447..932b4577e2f0f 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -527,7 +527,7 @@ static inline void fpregs_activate(struct fpu *fpu)
 static inline void
 switch_fpu_prepare(struct fpu *old_fpu, int cpu)
 {
-	if (static_cpu_has(X86_FEATURE_FPU) && old_fpu->initialized) {
+	if (static_cpu_has(X86_FEATURE_FPU) && current->mm) {
 		if (!copy_fpregs_to_fpstate(old_fpu))
 			old_fpu->last_cpu = -1;
 		else
@@ -535,8 +535,7 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu)
 
 		/* But leave fpu_fpregs_owner_ctx! */
 		trace_x86_fpu_regs_deactivated(old_fpu);
-	} else
-		old_fpu->last_cpu = -1;
+	}
 }
 
 /*
@@ -549,12 +548,12 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu)
  */
 static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
 {
-	bool preload = static_cpu_has(X86_FEATURE_FPU) &&
-		       new_fpu->initialized;
+	if (static_cpu_has(X86_FEATURE_FPU)) {
+		if (!fpregs_state_valid(new_fpu, cpu)) {
+			if (current->mm)
+				copy_kernel_to_fpregs(&new_fpu->state);
+		}
 
-	if (preload) {
-		if (!fpregs_state_valid(new_fpu, cpu))
-			copy_kernel_to_fpregs(&new_fpu->state);
 		fpregs_activate(new_fpu);
 	}
 }
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 202c53918ecfa..c5a6edd92de4f 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -293,15 +293,6 @@ struct fpu {
 	 */
 	unsigned int			last_cpu;
 
-	/*
-	 * @initialized:
-	 *
-	 * This flag indicates whether this context is initialized: if the task
-	 * is not running then we can restore from this context, if the task
-	 * is running then we should save into this context.
-	 */
-	unsigned char			initialized;
-
 	/*
 	 * @state:
 	 *
diff --git a/arch/x86/include/asm/trace/fpu.h b/arch/x86/include/asm/trace/fpu.h
index 069c04be15076..bd65f6ba950f8 100644
--- a/arch/x86/include/asm/trace/fpu.h
+++ b/arch/x86/include/asm/trace/fpu.h
@@ -13,22 +13,19 @@ DECLARE_EVENT_CLASS(x86_fpu,
 
 	TP_STRUCT__entry(
 		__field(struct fpu *, fpu)
-		__field(bool, initialized)
 		__field(u64, xfeatures)
 		__field(u64, xcomp_bv)
 		),
 
 	TP_fast_assign(
 		__entry->fpu		= fpu;
-		__entry->initialized	= fpu->initialized;
 		if (boot_cpu_has(X86_FEATURE_OSXSAVE)) {
 			__entry->xfeatures = fpu->state.xsave.header.xfeatures;
 			__entry->xcomp_bv  = fpu->state.xsave.header.xcomp_bv;
 		}
 	),
-	TP_printk("x86/fpu: %p initialized: %d xfeatures: %llx xcomp_bv: %llx",
+	TP_printk("x86/fpu: %p xfeatures: %llx xcomp_bv: %llx",
 			__entry->fpu,
-			__entry->initialized,
 			__entry->xfeatures,
 			__entry->xcomp_bv
 	)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index e43296854e379..3a4668c9d24f1 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -101,7 +101,7 @@ static void __kernel_fpu_begin(void)
 
 	kernel_fpu_disable();
 
-	if (fpu->initialized) {
+	if (current->mm) {
 		/*
 		 * Ignore return value -- we don't care if reg state
 		 * is clobbered.
@@ -116,7 +116,7 @@ static void __kernel_fpu_end(void)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
-	if (fpu->initialized)
+	if (current->mm)
 		copy_kernel_to_fpregs(&fpu->state);
 
 	kernel_fpu_enable();
@@ -147,10 +147,9 @@ void fpu__save(struct fpu *fpu)
 
 	preempt_disable();
 	trace_x86_fpu_before_save(fpu);
-	if (fpu->initialized) {
-		if (!copy_fpregs_to_fpstate(fpu)) {
-			copy_kernel_to_fpregs(&fpu->state);
-		}
+
+	if (!copy_fpregs_to_fpstate(fpu)) {
+		copy_kernel_to_fpregs(&fpu->state);
 	}
 	trace_x86_fpu_after_save(fpu);
 	preempt_enable();
@@ -190,7 +189,7 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 {
 	dst_fpu->last_cpu = -1;
 
-	if (!src_fpu->initialized || !static_cpu_has(X86_FEATURE_FPU))
+	if (!static_cpu_has(X86_FEATURE_FPU))
 		return 0;
 
 	WARN_ON_FPU(src_fpu != &current->thread.fpu);
@@ -227,14 +226,10 @@ static void fpu__initialize(struct fpu *fpu)
 {
 	WARN_ON_FPU(fpu != &current->thread.fpu);
 
-	if (!fpu->initialized) {
-		fpstate_init(&fpu->state);
-		trace_x86_fpu_init_state(fpu);
+	fpstate_init(&fpu->state);
+	trace_x86_fpu_init_state(fpu);
 
-		trace_x86_fpu_activate_state(fpu);
-		/* Safe to do for the current task: */
-		fpu->initialized = 1;
-	}
+	trace_x86_fpu_activate_state(fpu);
 }
 
 /*
@@ -247,32 +242,20 @@ static void fpu__initialize(struct fpu *fpu)
  *
  * - or it's called for stopped tasks (ptrace), in which case the
  *   registers were already saved by the context-switch code when
- *   the task scheduled out - we only have to initialize the registers
- *   if they've never been initialized.
+ *   the task scheduled out.
  *
  * If the task has used the FPU before then save it.
  */
 void fpu__prepare_read(struct fpu *fpu)
 {
-	if (fpu == &current->thread.fpu) {
+	if (fpu == &current->thread.fpu)
 		fpu__save(fpu);
-	} else {
-		if (!fpu->initialized) {
-			fpstate_init(&fpu->state);
-			trace_x86_fpu_init_state(fpu);
-
-			trace_x86_fpu_activate_state(fpu);
-			/* Safe to do for current and for stopped child tasks: */
-			fpu->initialized = 1;
-		}
-	}
 }
 
 /*
  * This function must be called before we write a task's fpstate.
  *
- * If the task has used the FPU before then invalidate any cached FPU registers.
- * If the task has not used the FPU before then initialize its fpstate.
+ * Invalidate any cached FPU registers.
  *
  * After this function call, after registers in the fpstate are
  * modified and the child task has woken up, the child task will
@@ -289,17 +272,8 @@ void fpu__prepare_write(struct fpu *fpu)
 	 */
 	WARN_ON_FPU(fpu == &current->thread.fpu);
 
-	if (fpu->initialized) {
-		/* Invalidate any cached state: */
-		__fpu_invalidate_fpregs_state(fpu);
-	} else {
-		fpstate_init(&fpu->state);
-		trace_x86_fpu_init_state(fpu);
-
-		trace_x86_fpu_activate_state(fpu);
-		/* Safe to do for stopped child tasks: */
-		fpu->initialized = 1;
-	}
+	/* Invalidate any cached state: */
+	__fpu_invalidate_fpregs_state(fpu);
 }
 
 /*
@@ -316,17 +290,13 @@ void fpu__drop(struct fpu *fpu)
 	preempt_disable();
 
 	if (fpu == &current->thread.fpu) {
-		if (fpu->initialized) {
-			/* Ignore delayed exceptions from user space */
-			asm volatile("1: fwait\n"
-				     "2:\n"
-				     _ASM_EXTABLE(1b, 2b));
-			fpregs_deactivate(fpu);
-		}
+		/* Ignore delayed exceptions from user space */
+		asm volatile("1: fwait\n"
+			     "2:\n"
+			     _ASM_EXTABLE(1b, 2b));
+		fpregs_deactivate(fpu);
 	}
 
-	fpu->initialized = 0;
-
 	trace_x86_fpu_dropped(fpu);
 
 	preempt_enable();
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index 6abd83572b016..20d8fa7124c77 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -239,8 +239,6 @@ static void __init fpu__init_system_ctx_switch(void)
 
 	WARN_ON_FPU(!on_boot_cpu);
 	on_boot_cpu = 0;
-
-	WARN_ON_FPU(current->thread.fpu.initialized);
 }
 
 /*
diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c
index 5dbc099178a88..d652b939ccfb5 100644
--- a/arch/x86/kernel/fpu/regset.c
+++ b/arch/x86/kernel/fpu/regset.c
@@ -15,16 +15,12 @@
  */
 int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
 {
-	struct fpu *target_fpu = &target->thread.fpu;
-
-	return target_fpu->initialized ? regset->n : 0;
+	return regset->n;
 }
 
 int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset)
 {
-	struct fpu *target_fpu = &target->thread.fpu;
-
-	if (boot_cpu_has(X86_FEATURE_FXSR) && target_fpu->initialized)
+	if (boot_cpu_has(X86_FEATURE_FXSR))
 		return regset->n;
 	else
 		return 0;
@@ -370,16 +366,9 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 int dump_fpu(struct pt_regs *regs, struct user_i387_struct *ufpu)
 {
 	struct task_struct *tsk = current;
-	struct fpu *fpu = &tsk->thread.fpu;
-	int fpvalid;
 
-	fpvalid = fpu->initialized;
-	if (fpvalid)
-		fpvalid = !fpregs_get(tsk, NULL,
-				      0, sizeof(struct user_i387_ia32_struct),
-				      ufpu, NULL);
-
-	return fpvalid;
+	return !fpregs_get(tsk, NULL, 0, sizeof(struct user_i387_ia32_struct),
+			   ufpu, NULL);
 }
 EXPORT_SYMBOL(dump_fpu);
 
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 359564beab5c3..a85f4139f663d 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -892,8 +892,6 @@ const void *get_xsave_field_ptr(int xsave_state)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
-	if (!fpu->initialized)
-		return NULL;
 	/*
 	 * fpu__save() takes the CPU's xstate registers
 	 * and saves them off to the 'fpu memory buffer.
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index b8a935adc96fc..5c99e49c0d392 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -292,10 +292,10 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	if (prev->gs | next->gs)
 		lazy_load_gs(next->gs);
 
-	switch_fpu_finish(next_fpu, cpu);
-
 	this_cpu_write(current_task, next_p);
 
+	switch_fpu_finish(next_fpu, cpu);
+
 	/* Load the Intel cache allocation PQR MSR. */
 	intel_rdt_sched_in();
 
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index cf2c157714594..4fd0dfa5bd83e 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -604,14 +604,14 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 
 	x86_fsgsbase_load(prev, next);
 
-	switch_fpu_finish(next_fpu, cpu);
-
 	/*
 	 * Switch the PDA and FPU contexts.
 	 */
 	this_cpu_write(current_task, next_p);
 	this_cpu_write(cpu_current_top_of_stack, task_top_of_stack(next_p));
 
+	switch_fpu_finish(next_fpu, cpu);
+
 	/* Reload sp0. */
 	update_task_stack(next_p);
 
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 92a3b312a53c4..2687e698c31fc 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -246,7 +246,7 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 	unsigned long sp = regs->sp;
 	unsigned long buf_fx = 0;
 	int onsigstack = on_sig_stack(sp);
-	struct fpu *fpu = &current->thread.fpu;
+	int ret;
 
 	/* redzone */
 	if (IS_ENABLED(CONFIG_X86_64))
@@ -265,11 +265,9 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 		sp = (unsigned long) ka->sa.sa_restorer;
 	}
 
-	if (fpu->initialized) {
-		sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
-					  &buf_fx, &math_size);
-		*fpstate = (void __user *)sp;
-	}
+	sp = fpu__alloc_mathframe(sp, IS_ENABLED(CONFIG_X86_32),
+				  &buf_fx, &math_size);
+	*fpstate = (void __user *)sp;
 
 	sp = align_sigframe(sp - frame_size);
 
@@ -281,8 +279,8 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs *regs, size_t frame_size,
 		return (void __user *)-1L;
 
 	/* save i387 and extended state */
-	if (fpu->initialized &&
-	    copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size) < 0)
+	ret = copy_fpstate_to_sigframe(*fpstate, (void __user *)buf_fx, math_size);
+	if (ret < 0)
 		return (void __user *)-1L;
 
 	return (void __user *)sp;
@@ -763,8 +761,7 @@ handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 		/*
 		 * Ensure the signal handler starts with the new fpu state.
 		 */
-		if (fpu->initialized)
-			fpu__clear(fpu);
+		fpu__clear(fpu);
 	}
 	signal_setup_done(failed, ksig, stepping);
 }
diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index 047a77f6a10cb..05bb9a44eb1c3 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -39,17 +39,12 @@ int __execute_only_pkey(struct mm_struct *mm)
 	 * dance to set PKRU if we do not need to.  Check it
 	 * first and assume that if the execute-only pkey is
 	 * write-disabled that we do not have to set it
-	 * ourselves.  We need preempt off so that nobody
-	 * can make fpregs inactive.
+	 * ourselves.
 	 */
-	preempt_disable();
 	if (!need_to_set_mm_pkey &&
-	    current->thread.fpu.initialized &&
 	    !__pkru_allows_read(read_pkru(), execute_only_pkey)) {
-		preempt_enable();
 		return execute_only_pkey;
 	}
-	preempt_enable();
 
 	/*
 	 * Set up PKRU so that it denies access for everything
-- 
2.20.0.rc1

[PATCH 15/29] x86/fpu: Remove user_fpu_begin()

[Sebastian Andrzej Siewior]

user_fpu_begin() sets fpu_fpregs_owner_ctx to task's fpu struct. This is
always the case since there is no lazy FPU anymore.

fpu_fpregs_owner_ctx is used during context switch to decide if it needs
to load the saved registers or if the currently loaded registers are
valid. It could be skipped during
	taskA -> kernel thread -> taskA

because the switch to kernel thread would not alter the CPU's FPU state.

Since this field is always updated during context switch and never
invalidated, setting it manually (in user context) makes no difference.
A kernel thread with kernel_fpu_begin() block could set
fpu_fpregs_owner_ctx to NULL but a kernel thread does not use
user_fpu_begin().
This is a leftover from the lazy-FPU time.

Remove user_fpu_begin(), it does not change fpu_fpregs_owner_ctx's
content.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/internal.h | 17 -----------------
 arch/x86/kernel/fpu/core.c          |  4 +---
 arch/x86/kernel/fpu/signal.c        |  1 -
 3 files changed, 1 insertion(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 932b4577e2f0f..a8b4c1e92c010 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -558,23 +558,6 @@ static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
 	}
 }
 
-/*
- * Needs to be preemption-safe.
- *
- * NOTE! user_fpu_begin() must be used only immediately before restoring
- * the save state. It does not do any saving/restoring on its own. In
- * lazy FPU mode, it is just an optimization to avoid a #NM exception,
- * the task can lose the FPU right after preempt_enable().
- */
-static inline void user_fpu_begin(void)
-{
-	struct fpu *fpu = &current->thread.fpu;
-
-	preempt_disable();
-	fpregs_activate(fpu);
-	preempt_enable();
-}
-
 /*
  * MXCSR and XCR definitions:
  */
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 3a4668c9d24f1..78d8037635932 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -335,10 +335,8 @@ void fpu__clear(struct fpu *fpu)
 	 * Make sure fpstate is cleared and initialized.
 	 */
 	fpu__initialize(fpu);
-	if (static_cpu_has(X86_FEATURE_FPU)) {
-		user_fpu_begin();
+	if (static_cpu_has(X86_FEATURE_FPU))
 		copy_init_fpstate_to_fpregs();
-	}
 }
 
 /*
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 3a59c578440e2..5f42de8a21deb 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -325,7 +325,6 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		 * For 64-bit frames and 32-bit fsave frames, restore the user
 		 * state to the registers directly (with exceptions handled).
 		 */
-		user_fpu_begin();
 		if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
 			fpu__clear(fpu);
 			return -1;
-- 
2.20.0.rc1

[PATCH 16/29] x86/fpu: Add (__)make_fpregs_active helpers

[Sebastian Andrzej Siewior]

From: Rik van Riel <riel@surriel.com>

Add helper function that ensures the floating point registers for
the current task are active. Use with preemption disabled.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/api.h      | 11 +++++++++++
 arch/x86/include/asm/fpu/internal.h | 19 +++++++++++--------
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index d6e094c282779..d6522b5706bb5 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -10,6 +10,7 @@
 
 #ifndef _ASM_X86_FPU_API_H
 #define _ASM_X86_FPU_API_H
+#include <linux/preempt.h>
 
 /*
  * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
@@ -23,6 +24,16 @@ extern void kernel_fpu_begin(void);
 extern void kernel_fpu_end(void);
 extern bool irq_fpu_usable(void);
 
+static inline void __fpregs_changes_begin(void)
+{
+	preempt_disable();
+}
+
+static inline void __fpregs_changes_end(void)
+{
+	preempt_enable();
+}
+
 /*
  * Query the presence of one or more xfeatures. Works on any legacy CPU as well.
  *
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index a8b4c1e92c010..21a8b4f5a5efd 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -513,6 +513,15 @@ static inline void fpregs_activate(struct fpu *fpu)
 	trace_x86_fpu_regs_activated(fpu);
 }
 
+static inline void __fpregs_load_activate(struct fpu *fpu, int cpu)
+{
+	if (!fpregs_state_valid(fpu, cpu)) {
+		if (current->mm)
+			copy_kernel_to_fpregs(&fpu->state);
+		fpregs_activate(fpu);
+	}
+}
+
 /*
  * FPU state switching for scheduling.
  *
@@ -548,14 +557,8 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu)
  */
 static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
 {
-	if (static_cpu_has(X86_FEATURE_FPU)) {
-		if (!fpregs_state_valid(new_fpu, cpu)) {
-			if (current->mm)
-				copy_kernel_to_fpregs(&new_fpu->state);
-		}
-
-		fpregs_activate(new_fpu);
-	}
+	if (static_cpu_has(X86_FEATURE_FPU))
+		__fpregs_load_activate(new_fpu, cpu);
 }
 
 /*
-- 
2.20.0.rc1

[PATCH 17/29] x86/fpu: Make __raw_xsave_addr() use feature number instead of mask

[Sebastian Andrzej Siewior]

Most users of __raw_xsave_addr() use a feature number, shift it to a
mask and then __raw_xsave_addr() shifts it back to the feature number.

Make __raw_xsave_addr() use the feature number as an argument.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/xstate.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index a85f4139f663d..0e759a032c1c7 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -805,20 +805,18 @@ void fpu__resume_cpu(void)
 }
 
 /*
- * Given an xstate feature mask, calculate where in the xsave
+ * Given an xstate feature nr, calculate where in the xsave
  * buffer the state is.  Callers should ensure that the buffer
  * is valid.
  */
-void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
+static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
 {
-	int feature_nr = fls64(xstate_feature_mask) - 1;
-
-	if (!xfeature_enabled(feature_nr)) {
+	if (!xfeature_enabled(xfeature_nr)) {
 		WARN_ON_FPU(1);
 		return NULL;
 	}
 
-	return (void *)xsave + xstate_comp_offsets[feature_nr];
+	return (void *)xsave + xstate_comp_offsets[xfeature_nr];
 }
 /*
  * Given the xsave area and a state inside, this function returns the
@@ -840,6 +838,7 @@ void *__raw_xsave_addr(struct xregs_state *xsave, int xstate_feature_mask)
  */
 void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 {
+	int xfeature_nr;
 	/*
 	 * Do we even *have* xsave state?
 	 */
@@ -867,7 +866,8 @@ void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 	if (!(xsave->header.xfeatures & xstate_feature))
 		return NULL;
 
-	return __raw_xsave_addr(xsave, xstate_feature);
+	xfeature_nr = fls64(xstate_feature) - 1;
+	return __raw_xsave_addr(xsave, xfeature_nr);
 }
 EXPORT_SYMBOL_GPL(get_xsave_addr);
 
@@ -1014,7 +1014,7 @@ int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int of
 		 * Copy only in-use xstates:
 		 */
 		if ((header.xfeatures >> i) & 1) {
-			void *src = __raw_xsave_addr(xsave, 1 << i);
+			void *src = __raw_xsave_addr(xsave, i);
 
 			offset = xstate_offsets[i];
 			size = xstate_sizes[i];
@@ -1100,7 +1100,7 @@ int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned i
 		 * Copy only in-use xstates:
 		 */
 		if ((header.xfeatures >> i) & 1) {
-			void *src = __raw_xsave_addr(xsave, 1 << i);
+			void *src = __raw_xsave_addr(xsave, i);
 
 			offset = xstate_offsets[i];
 			size = xstate_sizes[i];
@@ -1157,7 +1157,7 @@ int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf)
 		u64 mask = ((u64)1 << i);
 
 		if (hdr.xfeatures & mask) {
-			void *dst = __raw_xsave_addr(xsave, 1 << i);
+			void *dst = __raw_xsave_addr(xsave, i);
 
 			offset = xstate_offsets[i];
 			size = xstate_sizes[i];
@@ -1211,7 +1211,7 @@ int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf)
 		u64 mask = ((u64)1 << i);
 
 		if (hdr.xfeatures & mask) {
-			void *dst = __raw_xsave_addr(xsave, 1 << i);
+			void *dst = __raw_xsave_addr(xsave, i);
 
 			offset = xstate_offsets[i];
 			size = xstate_sizes[i];
-- 
2.20.0.rc1

[PATCH 18/29] x86/fpu: Make get_xsave_field_ptr() and get_xsave_addr() use feature number instead of mask

[Sebastian Andrzej Siewior]

After changing the argument of __raw_xsave_addr() from a mask to number
Dave suggested to check if it makes sense to do the same for
get_xsave_addr(). As it turns out it does. Only get_xsave_addr() needs
the mask to check if the requested feature is part of what is
support/saved and then uses the number again. The shift operation is
cheaper compared to "find last bit set". Also, the feature number uses
less opcode space compared to the mask :)

Make get_xsave_addr() argument a xfeature number instead of mask and fix
up its callers.
As part of this use xfeature_nr and xfeature_mask consistently.
This results in changes to the kvm code as:
	feature -> xfeature_mask
	index -> xfeature_nr

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/xstate.h |  4 ++--
 arch/x86/kernel/fpu/xstate.c      | 23 +++++++++++------------
 arch/x86/kernel/traps.c           |  2 +-
 arch/x86/kvm/x86.c                | 28 ++++++++++++++--------------
 arch/x86/mm/mpx.c                 |  6 +++---
 5 files changed, 31 insertions(+), 32 deletions(-)

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 48581988d78c7..fbe41f808e5d8 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -46,8 +46,8 @@ extern void __init update_regset_xstate_info(unsigned int size,
 					     u64 xstate_mask);
 
 void fpu__xstate_clear_all_cpu_caps(void);
-void *get_xsave_addr(struct xregs_state *xsave, int xstate);
-const void *get_xsave_field_ptr(int xstate_field);
+void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr);
+const void *get_xsave_field_ptr(int xfeature_nr);
 int using_compacted_format(void);
 int copy_xstate_to_kernel(void *kbuf, struct xregs_state *xsave, unsigned int offset, unsigned int size);
 int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned int offset, unsigned int size);
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 0e759a032c1c7..d288e4d271b71 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -830,15 +830,15 @@ static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
  *
  * Inputs:
  *	xstate: the thread's storage area for all FPU data
- *	xstate_feature: state which is defined in xsave.h (e.g.
- *	XFEATURE_MASK_FP, XFEATURE_MASK_SSE, etc...)
+ *	xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
+ *	XFEATURE_SSE, etc...)
  * Output:
  *	address of the state in the xsave area, or NULL if the
  *	field is not present in the xsave buffer.
  */
-void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
+void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
 {
-	int xfeature_nr;
+	u64 xfeature_mask = 1ULL << xfeature_nr;
 	/*
 	 * Do we even *have* xsave state?
 	 */
@@ -850,11 +850,11 @@ void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 	 * have not enabled.  Remember that pcntxt_mask is
 	 * what we write to the XCR0 register.
 	 */
-	WARN_ONCE(!(xfeatures_mask & xstate_feature),
+	WARN_ONCE(!(xfeatures_mask & xfeature_mask),
 		  "get of unsupported state");
 	/*
 	 * This assumes the last 'xsave*' instruction to
-	 * have requested that 'xstate_feature' be saved.
+	 * have requested that 'xfeature_mask' be saved.
 	 * If it did not, we might be seeing and old value
 	 * of the field in the buffer.
 	 *
@@ -863,10 +863,9 @@ void *get_xsave_addr(struct xregs_state *xsave, int xstate_feature)
 	 * or because the "init optimization" caused it
 	 * to not be saved.
 	 */
-	if (!(xsave->header.xfeatures & xstate_feature))
+	if (!(xsave->header.xfeatures & xfeature_mask))
 		return NULL;
 
-	xfeature_nr = fls64(xstate_feature) - 1;
 	return __raw_xsave_addr(xsave, xfeature_nr);
 }
 EXPORT_SYMBOL_GPL(get_xsave_addr);
@@ -882,13 +881,13 @@ EXPORT_SYMBOL_GPL(get_xsave_addr);
  * Note that this only works on the current task.
  *
  * Inputs:
- *	@xsave_state: state which is defined in xsave.h (e.g. XFEATURE_MASK_FP,
- *	XFEATURE_MASK_SSE, etc...)
+ *	@xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP,
+ *	XFEATURE_SSE, etc...)
  * Output:
  *	address of the state in the xsave area or NULL if the state
  *	is not present or is in its 'init state'.
  */
-const void *get_xsave_field_ptr(int xsave_state)
+const void *get_xsave_field_ptr(int xfeature_nr)
 {
 	struct fpu *fpu = &current->thread.fpu;
 
@@ -898,7 +897,7 @@ const void *get_xsave_field_ptr(int xsave_state)
 	 */
 	fpu__save(fpu);
 
-	return get_xsave_addr(&fpu->state.xsave, xsave_state);
+	return get_xsave_addr(&fpu->state.xsave, xfeature_nr);
 }
 
 #ifdef CONFIG_ARCH_HAS_PKEYS
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9b7c4ca8f0a73..626853b2ac344 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -455,7 +455,7 @@ dotraplinkage void do_bounds(struct pt_regs *regs, long error_code)
 	 * which is all zeros which indicates MPX was not
 	 * responsible for the exception.
 	 */
-	bndcsr = get_xsave_field_ptr(XFEATURE_MASK_BNDCSR);
+	bndcsr = get_xsave_field_ptr(XFEATURE_BNDCSR);
 	if (!bndcsr)
 		goto exit_trap;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5cd5647120f2b..75301b439b6e4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3650,15 +3650,15 @@ static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
 	 */
 	valid = xstate_bv & ~XFEATURE_MASK_FPSSE;
 	while (valid) {
-		u64 feature = valid & -valid;
-		int index = fls64(feature) - 1;
-		void *src = get_xsave_addr(xsave, feature);
+		u64 xfeature_mask = valid & -valid;
+		int xfeature_nr = fls64(xfeature_mask) - 1;
+		void *src = get_xsave_addr(xsave, xfeature_nr);
 
 		if (src) {
 			u32 size, offset, ecx, edx;
-			cpuid_count(XSTATE_CPUID, index,
+			cpuid_count(XSTATE_CPUID, xfeature_nr,
 				    &size, &offset, &ecx, &edx);
-			if (feature == XFEATURE_MASK_PKRU)
+			if (xfeature_nr == XFEATURE_PKRU)
 				memcpy(dest + offset, &vcpu->arch.pkru,
 				       sizeof(vcpu->arch.pkru));
 			else
@@ -3666,7 +3666,7 @@ static void fill_xsave(u8 *dest, struct kvm_vcpu *vcpu)
 
 		}
 
-		valid -= feature;
+		valid -= xfeature_mask;
 	}
 }
 
@@ -3693,22 +3693,22 @@ static void load_xsave(struct kvm_vcpu *vcpu, u8 *src)
 	 */
 	valid = xstate_bv & ~XFEATURE_MASK_FPSSE;
 	while (valid) {
-		u64 feature = valid & -valid;
-		int index = fls64(feature) - 1;
-		void *dest = get_xsave_addr(xsave, feature);
+		u64 xfeature_mask = valid & -valid;
+		int xfeature_nr = fls64(xfeature_mask) - 1;
+		void *dest = get_xsave_addr(xsave, xfeature_nr);
 
 		if (dest) {
 			u32 size, offset, ecx, edx;
-			cpuid_count(XSTATE_CPUID, index,
+			cpuid_count(XSTATE_CPUID, xfeature_nr,
 				    &size, &offset, &ecx, &edx);
-			if (feature == XFEATURE_MASK_PKRU)
+			if (xfeature_nr == XFEATURE_PKRU)
 				memcpy(&vcpu->arch.pkru, src + offset,
 				       sizeof(vcpu->arch.pkru));
 			else
 				memcpy(dest, src + offset, size);
 		}
 
-		valid -= feature;
+		valid -= xfeature_mask;
 	}
 }
 
@@ -8704,11 +8704,11 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 		if (init_event)
 			kvm_put_guest_fpu(vcpu);
 		mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu.state.xsave,
-					XFEATURE_MASK_BNDREGS);
+					XFEATURE_BNDREGS);
 		if (mpx_state_buffer)
 			memset(mpx_state_buffer, 0, sizeof(struct mpx_bndreg_state));
 		mpx_state_buffer = get_xsave_addr(&vcpu->arch.guest_fpu.state.xsave,
-					XFEATURE_MASK_BNDCSR);
+					XFEATURE_BNDCSR);
 		if (mpx_state_buffer)
 			memset(mpx_state_buffer, 0, sizeof(struct mpx_bndcsr));
 		if (init_event)
diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c
index 2385538e80656..bcd55cc3050c2 100644
--- a/arch/x86/mm/mpx.c
+++ b/arch/x86/mm/mpx.c
@@ -142,7 +142,7 @@ int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs)
 		goto err_out;
 	}
 	/* get bndregs field from current task's xsave area */
-	bndregs = get_xsave_field_ptr(XFEATURE_MASK_BNDREGS);
+	bndregs = get_xsave_field_ptr(XFEATURE_BNDREGS);
 	if (!bndregs) {
 		err = -EINVAL;
 		goto err_out;
@@ -190,7 +190,7 @@ static __user void *mpx_get_bounds_dir(void)
 	 * The bounds directory pointer is stored in a register
 	 * only accessible if we first do an xsave.
 	 */
-	bndcsr = get_xsave_field_ptr(XFEATURE_MASK_BNDCSR);
+	bndcsr = get_xsave_field_ptr(XFEATURE_BNDCSR);
 	if (!bndcsr)
 		return MPX_INVALID_BOUNDS_DIR;
 
@@ -376,7 +376,7 @@ static int do_mpx_bt_fault(void)
 	const struct mpx_bndcsr *bndcsr;
 	struct mm_struct *mm = current->mm;
 
-	bndcsr = get_xsave_field_ptr(XFEATURE_MASK_BNDCSR);
+	bndcsr = get_xsave_field_ptr(XFEATURE_BNDCSR);
 	if (!bndcsr)
 		return -EINVAL;
 	/*
-- 
2.20.0.rc1

[PATCH 19/29] x86/fpu: Only write PKRU if it is different from current

[Sebastian Andrzej Siewior]

Dave Hansen says that the `wrpkru' is more expensive than `rdpkru'. It
has a higher cycle cost and it's also practically a (light) speculation
barrier.

As an optimisation read the current PKRU value and only write the new
one if it is different.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/special_insns.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index 43c029cdc3fe8..c2ccf71b22dd6 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -107,7 +107,7 @@ static inline u32 __read_pkru(void)
 	return pkru;
 }
 
-static inline void __write_pkru(u32 pkru)
+static inline void __write_pkru_insn(u32 pkru)
 {
 	u32 ecx = 0, edx = 0;
 
@@ -118,6 +118,17 @@ static inline void __write_pkru(u32 pkru)
 	asm volatile(".byte 0x0f,0x01,0xef\n\t"
 		     : : "a" (pkru), "c"(ecx), "d"(edx));
 }
+
+static inline void __write_pkru(u32 pkru)
+{
+	/*
+	 * Writting PKRU is expensive. Only write the PKRU value if it is
+	 * different from the current one.
+	 */
+	if (pkru == __read_pkru())
+		return;
+	__write_pkru_insn(pkru);
+}
 #else
 static inline u32 __read_pkru(void)
 {
-- 
2.20.0.rc1

[PATCH 20/29] x86/pkeys: Don't check if PKRU is zero before writting it

[Sebastian Andrzej Siewior]

write_pkru() checks if the current value is the same as the expected
value. So instead just checking if the current and new value is zero
(and skip the write in such a case) we can benefit from that.

Remove the zero check of PKRU, write_pkru() provides a similar check.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/mm/pkeys.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c
index 05bb9a44eb1c3..50f65fc1b9a3f 100644
--- a/arch/x86/mm/pkeys.c
+++ b/arch/x86/mm/pkeys.c
@@ -142,13 +142,6 @@ u32 init_pkru_value = PKRU_AD_KEY( 1) | PKRU_AD_KEY( 2) | PKRU_AD_KEY( 3) |
 void copy_init_pkru_to_fpregs(void)
 {
 	u32 init_pkru_value_snapshot = READ_ONCE(init_pkru_value);
-	/*
-	 * Any write to PKRU takes it out of the XSAVE 'init
-	 * state' which increases context switch cost.  Avoid
-	 * writing 0 when PKRU was already 0.
-	 */
-	if (!init_pkru_value_snapshot && !read_pkru())
-		return;
 	/*
 	 * Override the PKRU state that came from 'init_fpstate'
 	 * with the baseline from the process.
-- 
2.20.0.rc1

[PATCH 21/29] x86/fpu: Eager switch PKRU state

[Sebastian Andrzej Siewior]

From: Rik van Riel <riel@surriel.com>

While most of a task's FPU state is only needed in user space, the
protection keys need to be in place immediately after a context switch.

The reason is that any access to userspace memory while running in
kernel mode also need to abide by the memory permissions specified in
the protection keys.

The "eager switch" is a preparation for loading the FPU state on return
to userland. Instead of decoupling PKRU state from xstate I update PKRU
within xstate on write operations by the kernel.

The read/write_pkru() is moved to another header file so it can easily
accessed from pgtable.h and fpu/internal.h.

For user tasks we should always get the PKRU from the xsave area and it
should not change anything because the PKRU value was loaded as part of
FPU restore.
For kernel kernel threads we now will have the default "allow
everything" written.  Before this commit the kernel thread would end up
with a random value which it inherited from the previous user task.

Signed-off-by: Rik van Riel <riel@surriel.com>
[bigeasy: save pkru to xstate, no cache, don't use __raw_xsave_addr()]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/internal.h | 20 ++++++++++++++++++--
 arch/x86/include/asm/fpu/xstate.h   |  1 +
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 21a8b4f5a5efd..788b307e66233 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -557,8 +557,24 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu)
  */
 static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
 {
-	if (static_cpu_has(X86_FEATURE_FPU))
-		__fpregs_load_activate(new_fpu, cpu);
+	struct pkru_state *pk;
+	u32 pkru_val = 0;
+
+	if (!static_cpu_has(X86_FEATURE_FPU))
+		return;
+
+	__fpregs_load_activate(new_fpu, cpu);
+
+	if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
+		return;
+
+	if (current->mm) {
+		pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU);
+		WARN_ON_ONCE(!pk);
+		if (pk)
+			pkru_val = pk->pkru;
+	}
+	__write_pkru(pkru_val);
 }
 
 /*
diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index fbe41f808e5d8..4e18a837223ff 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -5,6 +5,7 @@
 #include <linux/types.h>
 #include <asm/processor.h>
 #include <linux/uaccess.h>
+#include <asm/user.h>
 
 /* Bit 63 of XCR0 is reserved for future expansion */
 #define XFEATURE_MASK_EXTEND	(~(XFEATURE_MASK_FPSSE | (1ULL << 63)))
-- 
2.20.0.rc1

[PATCH 22/29] x86/entry: Add TIF_NEED_FPU_LOAD

[Sebastian Andrzej Siewior]

Add TIF_NEED_FPU_LOAD. This is reserved for loading the FPU registers
before returning to userland. This flag must not be set for systems
without a FPU.
If this flag is cleared, the CPU's FPU register hold the current content
of current()'s FPU register. The in-memory copy (union fpregs_state) is
not valid.
If this flag is set, then all of CPU's FPU register may hold a random
value (except for PKRU) and it is required to load the content of the
FPU register on return to userland.

It is introduced now, so we can add code handling it now before adding
the main feature.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/thread_info.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index cd6920674b905..1e64222030612 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -83,6 +83,7 @@ struct thread_info {
 #define TIF_SYSCALL_EMU		6	/* syscall emulation active */
 #define TIF_SYSCALL_AUDIT	7	/* syscall auditing active */
 #define TIF_SECCOMP		8	/* secure computing */
+#define TIF_NEED_FPU_LOAD	10	/* load FPU on return to userspace */
 #define TIF_USER_RETURN_NOTIFY	11	/* notify kernel of userspace return */
 #define TIF_UPROBE		12	/* breakpointed or singlestepping */
 #define TIF_PATCH_PENDING	13	/* pending live patching update */
@@ -110,6 +111,7 @@ struct thread_info {
 #define _TIF_SYSCALL_EMU	(1 << TIF_SYSCALL_EMU)
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
+#define _TIF_NEED_FPU_LOAD	(1 << TIF_NEED_FPU_LOAD)
 #define _TIF_USER_RETURN_NOTIFY	(1 << TIF_USER_RETURN_NOTIFY)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
 #define _TIF_PATCH_PENDING	(1 << TIF_PATCH_PENDING)
-- 
2.20.0.rc1

[PATCH 23/29] x86/fpu: Always store the registers in copy_fpstate_to_sigframe()

[Sebastian Andrzej Siewior]

From: Rik van Riel <riel@surriel.com>

copy_fpstate_to_sigframe() stores the registers directly to user space.
This is okay because the FPU register are valid and saving it directly
avoids saving it into kernel memory and making a copy.
However… We can't keep doing this if we are going to restore the FPU
registers on the return to userland. It is possible that the FPU
registers will be invalidated in the middle of the save operation and
this should be done with disabled preemption / BH.

Save the FPU registers to task's FPU struct and copy them to the user
memory later on.

This code is extracted from an earlier version of the patchset while
there still was lazy-FPU on x86.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/internal.h | 45 -----------------------------
 arch/x86/kernel/fpu/signal.c        | 29 +++++++------------
 2 files changed, 10 insertions(+), 64 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 788b307e66233..1e038b7357485 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -124,22 +124,6 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu);
 		     _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_fprestore)	\
 		     : output : input)
 
-static inline int copy_fregs_to_user(struct fregs_state __user *fx)
-{
-	return user_insn(fnsave %[fx]; fwait,  [fx] "=m" (*fx), "m" (*fx));
-}
-
-static inline int copy_fxregs_to_user(struct fxregs_state __user *fx)
-{
-	if (IS_ENABLED(CONFIG_X86_32))
-		return user_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx));
-	else if (IS_ENABLED(CONFIG_AS_FXSAVEQ))
-		return user_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx));
-
-	/* See comment in copy_fxregs_to_kernel() below. */
-	return user_insn(rex64/fxsave (%[fx]), "=m" (*fx), [fx] "R" (fx));
-}
-
 static inline void copy_kernel_to_fxregs(struct fxregs_state *fx)
 {
 	if (IS_ENABLED(CONFIG_X86_32)) {
@@ -350,35 +334,6 @@ static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask)
 	XSTATE_XRESTORE(xstate, lmask, hmask);
 }
 
-/*
- * Save xstate to user space xsave area.
- *
- * We don't use modified optimization because xrstor/xrstors might track
- * a different application.
- *
- * We don't use compacted format xsave area for
- * backward compatibility for old applications which don't understand
- * compacted format of xsave area.
- */
-static inline int copy_xregs_to_user(struct xregs_state __user *buf)
-{
-	int err;
-
-	/*
-	 * Clear the xsave header first, so that reserved fields are
-	 * initialized to zero.
-	 */
-	err = __clear_user(&buf->header, sizeof(buf->header));
-	if (unlikely(err))
-		return -EFAULT;
-
-	stac();
-	XSTATE_OP(XSAVE, buf, -1, -1, err);
-	clac();
-
-	return err;
-}
-
 /*
  * Restore xstate from user space xsave area.
  */
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 5f42de8a21deb..d8c2242877040 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -118,22 +118,6 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
 	return err;
 }
 
-static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
-{
-	int err;
-
-	if (use_xsave())
-		err = copy_xregs_to_user(buf);
-	else if (use_fxsr())
-		err = copy_fxregs_to_user((struct fxregs_state __user *) buf);
-	else
-		err = copy_fregs_to_user((struct fregs_state __user *) buf);
-
-	if (unlikely(err) && __clear_user(buf, fpu_user_xstate_size))
-		err = -EFAULT;
-	return err;
-}
-
 /*
  * Save the fpu, extended register state to the user signal frame.
  *
@@ -157,6 +141,7 @@ static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf)
 int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 {
 	struct fpu *fpu = &current->thread.fpu;
+	struct xregs_state *xsave = &fpu->state.xsave;
 	struct task_struct *tsk = current;
 	int ia32_fxstate = (buf != buf_fx);
 
@@ -171,9 +156,15 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 			sizeof(struct user_i387_ia32_struct), NULL,
 			(struct _fpstate_32 __user *) buf) ? -1 : 1;
 
-	/* Save the live register state to the user directly. */
-	if (copy_fpregs_to_sigframe(buf_fx))
-		return -1;
+	copy_fpregs_to_fpstate(fpu);
+
+	if (using_compacted_format()) {
+		copy_xstate_to_user(buf_fx, xsave, 0, size);
+	} else {
+		fpstate_sanitize_xstate(fpu);
+		if (__copy_to_user(buf_fx, xsave, fpu_user_xstate_size))
+			return -1;
+	}
 
 	/* Save the fsave header for the 32-bit frames. */
 	if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf))
-- 
2.20.0.rc1

[PATCH 24/29] x86/fpu: Prepare copy_fpstate_to_sigframe() for TIF_NEED_FPU_LOAD

[Sebastian Andrzej Siewior]

From: Rik van Riel <riel@surriel.com>

The FPU registers need only to be saved if TIF_NEED_FPU_LOAD is not set.
Otherwise this has been already done and can be skipped.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/signal.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index d8c2242877040..6e516eeaea328 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -156,7 +156,16 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size)
 			sizeof(struct user_i387_ia32_struct), NULL,
 			(struct _fpstate_32 __user *) buf) ? -1 : 1;
 
-	copy_fpregs_to_fpstate(fpu);
+	__fpregs_changes_begin();
+	/*
+	 * If we do not need to load the FPU registers at return to userspace
+	 * then the CPU has the current state and we need to save it. Otherwise
+	 * it is already done and we can skip it.
+	 */
+	if (!test_thread_flag(TIF_NEED_FPU_LOAD))
+		copy_fpregs_to_fpstate(fpu);
+
+	__fpregs_changes_end();
 
 	if (using_compacted_format()) {
 		copy_xstate_to_user(buf_fx, xsave, 0, size);
-- 
2.20.0.rc1

[PATCH 25/29] x86/fpu: Update xstate's PKRU value on write_pkru()

[Sebastian Andrzej Siewior]

During the context switch the xstate is loaded which also includes the
PKRU value.
If xstate is restored on return to userland it is required that the
PKRU value in xstate is the same as the one in the CPU.

Save the PKRU in xstate during modification.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/pgtable.h | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 40616e8052924..5eed44798ae95 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -23,6 +23,8 @@
 
 #ifndef __ASSEMBLY__
 #include <asm/x86_init.h>
+#include <asm/fpu/xstate.h>
+#include <asm/fpu/api.h>
 
 extern pgd_t early_top_pgt[PTRS_PER_PGD];
 int __init __early_make_pgtable(unsigned long address, pmdval_t pmd);
@@ -133,8 +135,22 @@ static inline u32 read_pkru(void)
 
 static inline void write_pkru(u32 pkru)
 {
-	if (boot_cpu_has(X86_FEATURE_OSPKE))
-		__write_pkru(pkru);
+	struct pkru_state *pk;
+
+	if (!boot_cpu_has(X86_FEATURE_OSPKE))
+		return;
+
+	pk = get_xsave_addr(&current->thread.fpu.state.xsave, XFEATURE_PKRU);
+	/*
+	 * The PKRU value in xstate needs to be in sync with the value that is
+	 * written to the CPU. The FPU restore on return to userland would
+	 * otherwise load the previous value again.
+	 */
+	__fpregs_changes_begin();
+	if (pk)
+		pk->pkru = pkru;
+	__write_pkru(pkru);
+	__fpregs_changes_end();
 }
 
 static inline int pte_young(pte_t pte)
-- 
2.20.0.rc1

[PATCH 26/29] x86/fpu: Inline copy_user_to_fpregs_zeroing()

[Sebastian Andrzej Siewior]

Start refactoring __fpu__restore_sig() by inlining
copy_user_to_fpregs_zeroing().

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/signal.c | 42 ++++++++++++++++--------------------
 1 file changed, 19 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 6e516eeaea328..c66356b168b39 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -221,28 +221,6 @@ sanitize_restored_xstate(union fpregs_state *state,
 	}
 }
 
-/*
- * Restore the extended state if present. Otherwise, restore the FP/SSE state.
- */
-static inline int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only)
-{
-	if (use_xsave()) {
-		if ((unsigned long)buf % 64 || fx_only) {
-			u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
-			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-			return copy_user_to_fxregs(buf);
-		} else {
-			u64 init_bv = xfeatures_mask & ~xbv;
-			if (unlikely(init_bv))
-				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-			return copy_user_to_xregs(buf, xbv);
-		}
-	} else if (use_fxsr()) {
-		return copy_user_to_fxregs(buf);
-	} else
-		return copy_user_to_fregs(buf);
-}
-
 static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 {
 	int ia32_fxstate = (buf != buf_fx);
@@ -321,11 +299,29 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		kfree(tmp);
 		return err;
 	} else {
+		int ret;
+
 		/*
 		 * For 64-bit frames and 32-bit fsave frames, restore the user
 		 * state to the registers directly (with exceptions handled).
 		 */
-		if (copy_user_to_fpregs_zeroing(buf_fx, xfeatures, fx_only)) {
+		if (use_xsave()) {
+			if ((unsigned long)buf_fx % 64 || fx_only) {
+				u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
+				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+				ret = copy_user_to_fxregs(buf_fx);
+			} else {
+				u64 init_bv = xfeatures_mask & ~xfeatures;
+				if (unlikely(init_bv))
+					copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+				ret = copy_user_to_xregs(buf_fx, xfeatures);
+			}
+		} else if (use_fxsr()) {
+			ret = copy_user_to_fxregs(buf_fx);
+		} else
+			ret = copy_user_to_fregs(buf_fx);
+
+		if (ret) {
 			fpu__clear(fpu);
 			return -1;
 		}
-- 
2.20.0.rc1

Re: [PATCH 26/29] x86/fpu: Inline copy_user_to_fpregs_zeroing()

[Joey Pabalinas]

[-- Attachment #1: Type: text/plain, Size: 325 bytes --]

On Wed, Nov 28, 2018 at 11:20:32PM +0100, Sebastian Andrzej Siewior wrote:
> Start refactoring __fpu__restore_sig() by inlining
> copy_user_to_fpregs_zeroing().
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>

-- 
Cheers,
Joey Pabalinas

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

[PATCH 27/29] x86/fpu: Let __fpu__restore_sig() restore the !32bit+fxsr frame from kernel memory

[Sebastian Andrzej Siewior]

The !32bit+fxsr case loads the new state from user memory. In case we
restore the FPU state on return to userland we can't do this. It would
be required to disable preemption in order to avoid a context switch
which would set TIF_NEED_FPU_LOAD. If this happens before the "restore"
operation then the loaded registers would become volatile.

Disabling preemption while accessing user memory requires to disable the
pagefault handler. An error during XRSTOR would then mean that either a
page fault occured (and we have to retry with enabled page fault
handler) or a #GP occured because the xstate is bogus (after all the
sig-handler can modify it).

In order to avoid that mess, copy the FPU state from userland, validate
it and then load it. The copy_users_…() helper are basically the old
helper except that they operate on kernel memory and the fault handler
just sets the error value and the caller handles it.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/include/asm/fpu/internal.h | 32 ++++++++++-----
 arch/x86/kernel/fpu/signal.c        | 62 +++++++++++++++++++++++------
 2 files changed, 71 insertions(+), 23 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 1e038b7357485..9fb2b8b811d22 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -118,6 +118,21 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu);
 	err;								\
 })
 
+#define kernel_insn_norestore(insn, output, input...)			\
+({									\
+	int err;							\
+	asm volatile("1:" #insn "\n\t"					\
+		     "2:\n"						\
+		     ".section .fixup,\"ax\"\n"				\
+		     "3:  movl $-1,%[err]\n"				\
+		     "    jmp  2b\n"					\
+		     ".previous\n"					\
+		     _ASM_EXTABLE(1b, 3b)				\
+		     : [err] "=r" (err), output				\
+		     : "0"(0), input);					\
+	err;								\
+})
+
 #define kernel_insn(insn, output, input...)				\
 	asm volatile("1:" #insn "\n\t"					\
 		     "2:\n"						\
@@ -138,15 +153,15 @@ static inline void copy_kernel_to_fxregs(struct fxregs_state *fx)
 	}
 }
 
-static inline int copy_user_to_fxregs(struct fxregs_state __user *fx)
+static inline int copy_users_to_fxregs(struct fxregs_state *fx)
 {
 	if (IS_ENABLED(CONFIG_X86_32))
-		return user_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
+		return kernel_insn_norestore(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx));
 	else if (IS_ENABLED(CONFIG_AS_FXSAVEQ))
-		return user_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
+		return kernel_insn_norestore(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx));
 
 	/* See comment in copy_fxregs_to_kernel() below. */
-	return user_insn(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
+	return kernel_insn_norestore(rex64/fxrstor (%[fx]), "=m" (*fx), [fx] "R" (fx),
 			  "m" (*fx));
 }
 
@@ -155,9 +170,9 @@ static inline void copy_kernel_to_fregs(struct fregs_state *fx)
 	kernel_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
 }
 
-static inline int copy_user_to_fregs(struct fregs_state __user *fx)
+static inline int copy_users_to_fregs(struct fregs_state *fx)
 {
-	return user_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
+	return kernel_insn_norestore(frstor %[fx], "=m" (*fx), [fx] "m" (*fx));
 }
 
 static inline void copy_fxregs_to_kernel(struct fpu *fpu)
@@ -337,16 +352,13 @@ static inline void copy_kernel_to_xregs(struct xregs_state *xstate, u64 mask)
 /*
  * Restore xstate from user space xsave area.
  */
-static inline int copy_user_to_xregs(struct xregs_state __user *buf, u64 mask)
+static inline int copy_users_to_xregs(struct xregs_state *xstate, u64 mask)
 {
-	struct xregs_state *xstate = ((__force struct xregs_state *)buf);
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
 	int err;
 
-	stac();
 	XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
-	clac();
 
 	return err;
 }
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index c66356b168b39..339a8c113517e 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -217,7 +217,8 @@ sanitize_restored_xstate(union fpregs_state *state,
 		 */
 		xsave->i387.mxcsr &= mxcsr_feature_mask;
 
-		convert_to_fxsr(&state->fxsave, ia32_env);
+		if (ia32_env)
+			convert_to_fxsr(&state->fxsave, ia32_env);
 	}
 }
 
@@ -299,28 +300,63 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		kfree(tmp);
 		return err;
 	} else {
+		union fpregs_state *state;
+		void *tmp;
 		int ret;
 
+		tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
+		if (!tmp)
+			return -ENOMEM;
+		state = PTR_ALIGN(tmp, 64);
+
 		/*
 		 * For 64-bit frames and 32-bit fsave frames, restore the user
 		 * state to the registers directly (with exceptions handled).
 		 */
-		if (use_xsave()) {
-			if ((unsigned long)buf_fx % 64 || fx_only) {
+		if ((unsigned long)buf_fx % 64)
+			fx_only = 1;
+
+		if (use_xsave() && !fx_only) {
+			u64 init_bv = xfeatures_mask & ~xfeatures;
+
+			if (using_compacted_format()) {
+				ret = copy_user_to_xstate(&state->xsave, buf_fx);
+			} else {
+				ret = __copy_from_user(&state->xsave, buf_fx, state_size);
+
+				if (!ret && state_size > offsetof(struct xregs_state, header))
+					ret = validate_xstate_header(&state->xsave.header);
+			}
+			if (ret)
+				goto err_out;
+			sanitize_restored_xstate(state, NULL, xfeatures,
+						 fx_only);
+
+			if (unlikely(init_bv))
+				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+			ret = copy_users_to_xregs(&state->xsave, xfeatures);
+
+		} else if (use_fxsr()) {
+			ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
+			if (ret)
+				goto err_out;
+
+			if (use_xsave()) {
 				u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
 				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-				ret = copy_user_to_fxregs(buf_fx);
-			} else {
-				u64 init_bv = xfeatures_mask & ~xfeatures;
-				if (unlikely(init_bv))
-					copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-				ret = copy_user_to_xregs(buf_fx, xfeatures);
 			}
-		} else if (use_fxsr()) {
-			ret = copy_user_to_fxregs(buf_fx);
-		} else
-			ret = copy_user_to_fregs(buf_fx);
+			state->fxsave.mxcsr &= mxcsr_feature_mask;
 
+			ret = copy_users_to_fxregs(&state->fxsave);
+		} else {
+			ret = __copy_from_user(&state->fsave, buf_fx, state_size);
+			if (ret)
+				goto err_out;
+			ret = copy_users_to_fregs(buf_fx);
+		}
+
+err_out:
+		kfree(tmp);
 		if (ret) {
 			fpu__clear(fpu);
 			return -1;
-- 
2.20.0.rc1

[PATCH 28/29] x86/fpu: Merge the two code paths in __fpu__restore_sig()

[Sebastian Andrzej Siewior]

The ia32_fxstate case (32bit with fxsr) and the other (64bit, 32bit
without fxsr) restore both from kernel memory and sanitize the content.
The !ia32_fxstate version restores missing xstates from "init state"
while the ia32_fxstate doesn't and skips it.

Merge the two code paths and keep the !ia32_fxstate version. Copy only
the user_i387_ia32_struct data structure in the ia32_fxstate.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/signal.c | 162 ++++++++++++++---------------------
 1 file changed, 65 insertions(+), 97 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 339a8c113517e..fb16d0da71bca 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -228,6 +228,11 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 	struct task_struct *tsk = current;
 	struct fpu *fpu = &tsk->thread.fpu;
 	int state_size = fpu_kernel_xstate_size;
+	union fpregs_state *state;
+	void *tmp;
+	struct user_i387_ia32_struct env;
+	struct user_i387_ia32_struct *envp = NULL;
+	int ret = 0;
 	u64 xfeatures = 0;
 	int fx_only = 0;
 
@@ -264,106 +269,69 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		}
 	}
 
+	tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
+	if (!tmp)
+		return -ENOMEM;
+	state = PTR_ALIGN(tmp, 64);
+
+	if ((unsigned long)buf_fx % 64)
+		fx_only = 1;
+
+	/*
+	 * For 32-bit frames with fxstate, copy the fxstate so it can be
+	 * reconstructed later.
+	 */
 	if (ia32_fxstate) {
-		/*
-		 * For 32-bit frames with fxstate, copy the user state to the
-		 * thread's fpu state, reconstruct fxstate from the fsave
-		 * header. Validate and sanitize the copied state.
-		 */
-		union fpregs_state *state;
-		void *tmp;
-		struct user_i387_ia32_struct env;
-		int err = 0;
-
-		tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
-		if (!tmp)
-			return -ENOMEM;
-		state = PTR_ALIGN(tmp, 64);
-
-		if (using_compacted_format()) {
-			err = copy_user_to_xstate(&state->xsave, buf_fx);
-		} else {
-			err = __copy_from_user(&state->xsave, buf_fx, state_size);
-
-			if (!err && state_size > offsetof(struct xregs_state, header))
-				err = validate_xstate_header(&state->xsave.header);
-		}
-
-		if (err || __copy_from_user(&env, buf, sizeof(env))) {
-			err = -1;
-		} else {
-			sanitize_restored_xstate(state, &env,
-						 xfeatures, fx_only);
-			copy_kernel_to_fpregs(state);
-		}
-
-		kfree(tmp);
-		return err;
-	} else {
-		union fpregs_state *state;
-		void *tmp;
-		int ret;
-
-		tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
-		if (!tmp)
-			return -ENOMEM;
-		state = PTR_ALIGN(tmp, 64);
-
-		/*
-		 * For 64-bit frames and 32-bit fsave frames, restore the user
-		 * state to the registers directly (with exceptions handled).
-		 */
-		if ((unsigned long)buf_fx % 64)
-			fx_only = 1;
-
-		if (use_xsave() && !fx_only) {
-			u64 init_bv = xfeatures_mask & ~xfeatures;
-
-			if (using_compacted_format()) {
-				ret = copy_user_to_xstate(&state->xsave, buf_fx);
-			} else {
-				ret = __copy_from_user(&state->xsave, buf_fx, state_size);
-
-				if (!ret && state_size > offsetof(struct xregs_state, header))
-					ret = validate_xstate_header(&state->xsave.header);
-			}
-			if (ret)
-				goto err_out;
-			sanitize_restored_xstate(state, NULL, xfeatures,
-						 fx_only);
-
-			if (unlikely(init_bv))
-				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-			ret = copy_users_to_xregs(&state->xsave, xfeatures);
-
-		} else if (use_fxsr()) {
-			ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
-			if (ret)
-				goto err_out;
-
-			if (use_xsave()) {
-				u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
-				copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-			}
-			state->fxsave.mxcsr &= mxcsr_feature_mask;
-
-			ret = copy_users_to_fxregs(&state->fxsave);
-		} else {
-			ret = __copy_from_user(&state->fsave, buf_fx, state_size);
-			if (ret)
-				goto err_out;
-			ret = copy_users_to_fregs(buf_fx);
-		}
-
-err_out:
-		kfree(tmp);
-		if (ret) {
-			fpu__clear(fpu);
-			return -1;
-		}
+		ret = __copy_from_user(&env, buf, sizeof(env));
+		if (ret)
+			goto err_out;
+		envp = &env;
 	}
 
-	return 0;
+	if (use_xsave() && !fx_only) {
+		u64 init_bv = xfeatures_mask & ~xfeatures;
+
+		if (using_compacted_format()) {
+			ret = copy_user_to_xstate(&state->xsave, buf_fx);
+		} else {
+			ret = __copy_from_user(&state->xsave, buf_fx, state_size);
+
+			if (!ret && state_size > offsetof(struct xregs_state, header))
+				ret = validate_xstate_header(&state->xsave.header);
+		}
+		if (ret)
+			goto err_out;
+
+		sanitize_restored_xstate(state, envp, xfeatures, fx_only);
+
+		if (unlikely(init_bv))
+			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+		ret = copy_users_to_xregs(&state->xsave, xfeatures);
+
+	} else if (use_fxsr()) {
+		ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
+		if (ret)
+			goto err_out;
+
+		sanitize_restored_xstate(state, envp, xfeatures, fx_only);
+		if (use_xsave()) {
+			u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
+			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
+		}
+
+		ret = copy_users_to_fxregs(&state->fxsave);
+	} else {
+		ret = __copy_from_user(&state->fsave, buf_fx, state_size);
+		if (ret)
+			goto err_out;
+		ret = copy_users_to_fregs(buf_fx);
+	}
+
+err_out:
+	kfree(tmp);
+	if (ret)
+		fpu__clear(fpu);
+	return ret;
 }
 
 static inline int xstate_sigframe_size(void)
-- 
2.20.0.rc1

[PATCH 29/29] x86/fpu: Defer FPU state load until return to userspace

[Sebastian Andrzej Siewior]

From: Rik van Riel <riel@surriel.com>

Defer loading of FPU state until return to userspace. This gives
the kernel the potential to skip loading FPU state for tasks that
stay in kernel mode, or for tasks that end up with repeated
invocations of kernel_fpu_begin() & kernel_fpu_end().

The __fpregs_changes_{begin|end}() section ensures that the register
remain unchanged. Otherwise a context switch or a BH could save the
registers to its FPU context and processor's FPU register would became
random if beeing modified at the same time.

KVM swaps the host/guest register on entry/exit path. I kept the flow as
is. First it ensures that the registers are loaded and then saves the
current (host) state before it loads the guest's register. The swap is
done at the very end with disabled interrupts so it should not change
anymore before theg guest is entered. The read/save version seems to be
cheaper compared to memcpy() in a micro benchmark.

Each thread gets TIF_NEED_FPU_LOAD set as part of fork() / fpu__copy().
For kernel threads, this flag gets never cleared which avoids saving /
restoring the FPU state for kernel threads and during in-kernel usage of
the FPU register.

Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/entry/common.c             |   8 +++
 arch/x86/include/asm/fpu/api.h      |  22 +++++-
 arch/x86/include/asm/fpu/internal.h |  27 +++++---
 arch/x86/include/asm/trace/fpu.h    |   5 +-
 arch/x86/kernel/fpu/core.c          | 104 +++++++++++++++++++++-------
 arch/x86/kernel/fpu/signal.c        |  47 ++++++++-----
 arch/x86/kernel/process.c           |   2 +-
 arch/x86/kernel/process_32.c        |   5 +-
 arch/x86/kernel/process_64.c        |   5 +-
 arch/x86/kvm/x86.c                  |  19 +++--
 10 files changed, 179 insertions(+), 65 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 3b2490b819181..e46fe9aa2934a 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -31,6 +31,7 @@
 #include <asm/vdso.h>
 #include <linux/uaccess.h>
 #include <asm/cpufeature.h>
+#include <asm/fpu/api.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/syscalls.h>
@@ -196,6 +197,13 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs)
 	if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))
 		exit_to_usermode_loop(regs, cached_flags);
 
+	/* Reload ti->flags; we may have rescheduled above. */
+	cached_flags = READ_ONCE(ti->flags);
+
+	fpregs_assert_state_consistent();
+	if (unlikely(cached_flags & _TIF_NEED_FPU_LOAD))
+		switch_fpu_return();
+
 #ifdef CONFIG_COMPAT
 	/*
 	 * Compat syscalls set TS_COMPAT.  Make sure we clear it before
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index d6522b5706bb5..b1c282845446e 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -10,7 +10,7 @@
 
 #ifndef _ASM_X86_FPU_API_H
 #define _ASM_X86_FPU_API_H
-#include <linux/preempt.h>
+#include <linux/bottom_half.h>
 
 /*
  * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It
@@ -23,17 +23,37 @@
 extern void kernel_fpu_begin(void);
 extern void kernel_fpu_end(void);
 extern bool irq_fpu_usable(void);
+extern void fpregs_mark_activate(void);
 
+/*
+ * Use __fpregs_changes_begin() while editing CPU's FPU registers or fpu->state.
+ * A context switch will (and softirq might) save CPU's FPU register to
+ * fpu->state and set TIF_NEED_FPU_LOAD leaving CPU's FPU registers in a random
+ * state.
+ */
 static inline void __fpregs_changes_begin(void)
 {
 	preempt_disable();
+	local_bh_disable();
 }
 
 static inline void __fpregs_changes_end(void)
 {
+	local_bh_enable();
 	preempt_enable();
 }
 
+#ifdef CONFIG_X86_DEBUG_FPU
+extern void fpregs_assert_state_consistent(void);
+#else
+static inline void fpregs_assert_state_consistent(void) { }
+#endif
+
+/*
+ * Load the task FPU state before returning to userspace.
+ */
+extern void switch_fpu_return(void);
+
 /*
  * Query the presence of one or more xfeatures. Works on any legacy CPU as well.
  *
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 9fb2b8b811d22..6a9220efb58b3 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -29,7 +29,7 @@ extern void fpu__prepare_write(struct fpu *fpu);
 extern void fpu__save(struct fpu *fpu);
 extern int  fpu__restore_sig(void __user *buf, int ia32_frame);
 extern void fpu__drop(struct fpu *fpu);
-extern int  fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu);
+extern int  fpu__copy(struct task_struct *dst, struct task_struct *src);
 extern void fpu__clear(struct fpu *fpu);
 extern int  fpu__exception_code(struct fpu *fpu, int trap_nr);
 extern int  dump_fpu(struct pt_regs *ptregs, struct user_i387_struct *fpstate);
@@ -480,13 +480,20 @@ static inline void fpregs_activate(struct fpu *fpu)
 	trace_x86_fpu_regs_activated(fpu);
 }
 
-static inline void __fpregs_load_activate(struct fpu *fpu, int cpu)
+static inline void __fpregs_load_activate(void)
 {
+	struct fpu *fpu = &current->thread.fpu;
+	int cpu = smp_processor_id();
+
+	if (WARN_ON_ONCE(current->mm == NULL))
+		return;
+
 	if (!fpregs_state_valid(fpu, cpu)) {
-		if (current->mm)
-			copy_kernel_to_fpregs(&fpu->state);
+		copy_kernel_to_fpregs(&fpu->state);
 		fpregs_activate(fpu);
+		fpu->last_cpu = cpu;
 	}
+	clear_thread_flag(TIF_NEED_FPU_LOAD);
 }
 
 /*
@@ -497,8 +504,8 @@ static inline void __fpregs_load_activate(struct fpu *fpu, int cpu)
  *  - switch_fpu_prepare() saves the old state.
  *    This is done within the context of the old process.
  *
- *  - switch_fpu_finish() restores the new state as
- *    necessary.
+ *  - switch_fpu_finish() sets TIF_NEED_FPU_LOAD; the floating point state
+ *    will get loaded on return to userspace, or when the kernel needs it.
  */
 static inline void
 switch_fpu_prepare(struct fpu *old_fpu, int cpu)
@@ -519,10 +526,10 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu)
  */
 
 /*
- * Set up the userspace FPU context for the new task, if the task
- * has used the FPU.
+ * Load PKRU from the FPU context if available. Delay loading the loading of the
+ * complete FPU state until the return to userland.
  */
-static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
+static inline void switch_fpu_finish(struct fpu *new_fpu)
 {
 	struct pkru_state *pk;
 	u32 pkru_val = 0;
@@ -530,7 +537,7 @@ static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu)
 	if (!static_cpu_has(X86_FEATURE_FPU))
 		return;
 
-	__fpregs_load_activate(new_fpu, cpu);
+	set_thread_flag(TIF_NEED_FPU_LOAD);
 
 	if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
 		return;
diff --git a/arch/x86/include/asm/trace/fpu.h b/arch/x86/include/asm/trace/fpu.h
index bd65f6ba950f8..91a1422091ceb 100644
--- a/arch/x86/include/asm/trace/fpu.h
+++ b/arch/x86/include/asm/trace/fpu.h
@@ -13,19 +13,22 @@ DECLARE_EVENT_CLASS(x86_fpu,
 
 	TP_STRUCT__entry(
 		__field(struct fpu *, fpu)
+		__field(bool, load_fpu)
 		__field(u64, xfeatures)
 		__field(u64, xcomp_bv)
 		),
 
 	TP_fast_assign(
 		__entry->fpu		= fpu;
+		__entry->load_fpu	= test_thread_flag(TIF_NEED_FPU_LOAD);
 		if (boot_cpu_has(X86_FEATURE_OSXSAVE)) {
 			__entry->xfeatures = fpu->state.xsave.header.xfeatures;
 			__entry->xcomp_bv  = fpu->state.xsave.header.xcomp_bv;
 		}
 	),
-	TP_printk("x86/fpu: %p xfeatures: %llx xcomp_bv: %llx",
+	TP_printk("x86/fpu: %p load: %d xfeatures: %llx xcomp_bv: %llx",
 			__entry->fpu,
+			__entry->load_fpu,
 			__entry->xfeatures,
 			__entry->xcomp_bv
 	)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 78d8037635932..f52e687dff9ee 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -102,23 +102,20 @@ static void __kernel_fpu_begin(void)
 	kernel_fpu_disable();
 
 	if (current->mm) {
-		/*
-		 * Ignore return value -- we don't care if reg state
-		 * is clobbered.
-		 */
-		copy_fpregs_to_fpstate(fpu);
-	} else {
-		__cpu_invalidate_fpregs_state();
+		if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
+			set_thread_flag(TIF_NEED_FPU_LOAD);
+			/*
+			 * Ignore return value -- we don't care if reg state
+			 * is clobbered.
+			 */
+			copy_fpregs_to_fpstate(fpu);
+		}
 	}
+	__cpu_invalidate_fpregs_state();
 }
 
 static void __kernel_fpu_end(void)
 {
-	struct fpu *fpu = &current->thread.fpu;
-
-	if (current->mm)
-		copy_kernel_to_fpregs(&fpu->state);
-
 	kernel_fpu_enable();
 }
 
@@ -145,14 +142,16 @@ void fpu__save(struct fpu *fpu)
 {
 	WARN_ON_FPU(fpu != &current->thread.fpu);
 
-	preempt_disable();
+	__fpregs_changes_begin();
 	trace_x86_fpu_before_save(fpu);
 
-	if (!copy_fpregs_to_fpstate(fpu)) {
-		copy_kernel_to_fpregs(&fpu->state);
+	if (!test_thread_flag(TIF_NEED_FPU_LOAD)) {
+		if (!copy_fpregs_to_fpstate(fpu)) {
+			copy_kernel_to_fpregs(&fpu->state);
+		}
 	}
 	trace_x86_fpu_after_save(fpu);
-	preempt_enable();
+	__fpregs_changes_end();
 }
 EXPORT_SYMBOL_GPL(fpu__save);
 
@@ -185,8 +184,11 @@ void fpstate_init(union fpregs_state *state)
 }
 EXPORT_SYMBOL_GPL(fpstate_init);
 
-int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
+int fpu__copy(struct task_struct *dst, struct task_struct *src)
 {
+	struct fpu *dst_fpu = &dst->thread.fpu;
+	struct fpu *src_fpu = &src->thread.fpu;
+
 	dst_fpu->last_cpu = -1;
 
 	if (!static_cpu_has(X86_FEATURE_FPU))
@@ -201,16 +203,23 @@ int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
 	memset(&dst_fpu->state.xsave, 0, fpu_kernel_xstate_size);
 
 	/*
-	 * Save current FPU registers directly into the child
-	 * FPU context, without any memory-to-memory copying.
+	 * If the FPU registers are not current just memcpy() the state.
+	 * Otherwise save current FPU registers directly into the child's FPU
+	 * context, without any memory-to-memory copying.
 	 *
 	 * ( The function 'fails' in the FNSAVE case, which destroys
-	 *   register contents so we have to copy them back. )
+	 *   register contents so we have to load them back. )
 	 */
-	if (!copy_fpregs_to_fpstate(dst_fpu)) {
-		memcpy(&src_fpu->state, &dst_fpu->state, fpu_kernel_xstate_size);
-		copy_kernel_to_fpregs(&src_fpu->state);
-	}
+	__fpregs_changes_begin();
+	if (test_thread_flag(TIF_NEED_FPU_LOAD))
+		memcpy(&dst_fpu->state, &src_fpu->state, fpu_kernel_xstate_size);
+
+	else if (!copy_fpregs_to_fpstate(dst_fpu))
+		copy_kernel_to_fpregs(&dst_fpu->state);
+
+	__fpregs_changes_end();
+
+	set_tsk_thread_flag(dst, TIF_NEED_FPU_LOAD);
 
 	trace_x86_fpu_copy_src(src_fpu);
 	trace_x86_fpu_copy_dst(dst_fpu);
@@ -226,10 +235,9 @@ static void fpu__initialize(struct fpu *fpu)
 {
 	WARN_ON_FPU(fpu != &current->thread.fpu);
 
+	set_thread_flag(TIF_NEED_FPU_LOAD);
 	fpstate_init(&fpu->state);
 	trace_x86_fpu_init_state(fpu);
-
-	trace_x86_fpu_activate_state(fpu);
 }
 
 /*
@@ -308,6 +316,8 @@ void fpu__drop(struct fpu *fpu)
  */
 static inline void copy_init_fpstate_to_fpregs(void)
 {
+	__fpregs_changes_begin();
+
 	if (use_xsave())
 		copy_kernel_to_xregs(&init_fpstate.xsave, -1);
 	else if (static_cpu_has(X86_FEATURE_FXSR))
@@ -317,6 +327,9 @@ static inline void copy_init_fpstate_to_fpregs(void)
 
 	if (boot_cpu_has(X86_FEATURE_OSPKE))
 		copy_init_pkru_to_fpregs();
+
+	fpregs_mark_activate();
+	__fpregs_changes_end();
 }
 
 /*
@@ -339,6 +352,45 @@ void fpu__clear(struct fpu *fpu)
 		copy_init_fpstate_to_fpregs();
 }
 
+/*
+ * Load FPU context before returning to userspace.
+ */
+void switch_fpu_return(void)
+{
+	if (!static_cpu_has(X86_FEATURE_FPU))
+		return;
+
+	__fpregs_load_activate();
+}
+EXPORT_SYMBOL_GPL(switch_fpu_return);
+
+#ifdef CONFIG_X86_DEBUG_FPU
+/*
+ * If current FPU state according to its tracking (loaded FPU ctx on this CPU)
+ * is not valid then we must have TIF_NEED_FPU_LOAD set so the context is loaded on
+ * return to userland.
+ */
+void fpregs_assert_state_consistent(void)
+{
+       struct fpu *fpu = &current->thread.fpu;
+
+       if (test_thread_flag(TIF_NEED_FPU_LOAD))
+               return;
+       WARN_ON_FPU(!fpregs_state_valid(fpu, smp_processor_id()));
+}
+EXPORT_SYMBOL_GPL(fpregs_assert_state_consistent);
+#endif
+
+void fpregs_mark_activate(void)
+{
+	struct fpu *fpu = &current->thread.fpu;
+
+	fpregs_activate(fpu);
+	fpu->last_cpu = smp_processor_id();
+	clear_thread_flag(TIF_NEED_FPU_LOAD);
+}
+EXPORT_SYMBOL_GPL(fpregs_mark_activate);
+
 /*
  * x87 math exception handling:
  */
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index fb16d0da71bca..f552b1d6c6958 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -228,13 +228,12 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 	struct task_struct *tsk = current;
 	struct fpu *fpu = &tsk->thread.fpu;
 	int state_size = fpu_kernel_xstate_size;
-	union fpregs_state *state;
-	void *tmp;
 	struct user_i387_ia32_struct env;
 	struct user_i387_ia32_struct *envp = NULL;
 	int ret = 0;
 	u64 xfeatures = 0;
 	int fx_only = 0;
+	int err;
 
 	ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) ||
 			 IS_ENABLED(CONFIG_IA32_EMULATION));
@@ -269,14 +268,18 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		}
 	}
 
-	tmp = kzalloc(sizeof(*state) + fpu_kernel_xstate_size + 64, GFP_KERNEL);
-	if (!tmp)
-		return -ENOMEM;
-	state = PTR_ALIGN(tmp, 64);
+	/*
+	 * The current state of the FPU registers does not matter. By setting
+	 * TIF_NEED_FPU_LOAD unconditionally it is ensured that the our xstate
+	 * is not modified on context switch and that the xstate is considered
+	 * to loaded again on return to userland (overriding last_cpu avoids the
+	 * optimisation).
+	 */
+	set_thread_flag(TIF_NEED_FPU_LOAD);
+	__fpu_invalidate_fpregs_state(fpu);
 
 	if ((unsigned long)buf_fx % 64)
 		fx_only = 1;
-
 	/*
 	 * For 32-bit frames with fxstate, copy the fxstate so it can be
 	 * reconstructed later.
@@ -292,43 +295,51 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 		u64 init_bv = xfeatures_mask & ~xfeatures;
 
 		if (using_compacted_format()) {
-			ret = copy_user_to_xstate(&state->xsave, buf_fx);
+			ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
 		} else {
-			ret = __copy_from_user(&state->xsave, buf_fx, state_size);
+			ret = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
 
 			if (!ret && state_size > offsetof(struct xregs_state, header))
-				ret = validate_xstate_header(&state->xsave.header);
+				ret = validate_xstate_header(&fpu->state.xsave.header);
 		}
 		if (ret)
 			goto err_out;
 
-		sanitize_restored_xstate(state, envp, xfeatures, fx_only);
+		sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
 
+		__fpregs_changes_begin();
 		if (unlikely(init_bv))
 			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
-		ret = copy_users_to_xregs(&state->xsave, xfeatures);
+		ret = copy_users_to_xregs(&fpu->state.xsave, xfeatures);
 
 	} else if (use_fxsr()) {
-		ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
-		if (ret)
+		ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
+		if (ret) {
+			err = -EFAULT;
 			goto err_out;
+		}
 
-		sanitize_restored_xstate(state, envp, xfeatures, fx_only);
+		sanitize_restored_xstate(&fpu->state, &env, xfeatures, fx_only);
+
+		__fpregs_changes_begin();
 		if (use_xsave()) {
 			u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE;
 			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
 		}
 
-		ret = copy_users_to_fxregs(&state->fxsave);
+		ret = copy_users_to_fxregs(&fpu->state.fxsave);
 	} else {
-		ret = __copy_from_user(&state->fsave, buf_fx, state_size);
+		ret = __copy_from_user(&fpu->state.fsave, buf_fx, state_size);
 		if (ret)
 			goto err_out;
+		__fpregs_changes_begin();
 		ret = copy_users_to_fregs(buf_fx);
 	}
+	if (!ret)
+		fpregs_mark_activate();
+	__fpregs_changes_end();
 
 err_out:
-	kfree(tmp);
 	if (ret)
 		fpu__clear(fpu);
 	return ret;
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index c93fcfdf16734..cd7105fb92bfc 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -96,7 +96,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 	dst->thread.vm86 = NULL;
 #endif
 
-	return fpu__copy(&dst->thread.fpu, &src->thread.fpu);
+	return fpu__copy(dst, src);
 }
 
 /*
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 5c99e49c0d392..5c059ecb136db 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -233,7 +233,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 
 	/* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
 
-	switch_fpu_prepare(prev_fpu, cpu);
+	if (!test_thread_flag(TIF_NEED_FPU_LOAD))
+		switch_fpu_prepare(prev_fpu, cpu);
 
 	/*
 	 * Save away %gs. No need to save %fs, as it was saved on the
@@ -294,7 +295,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 
 	this_cpu_write(current_task, next_p);
 
-	switch_fpu_finish(next_fpu, cpu);
+	switch_fpu_finish(next_fpu);
 
 	/* Load the Intel cache allocation PQR MSR. */
 	intel_rdt_sched_in();
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 4fd0dfa5bd83e..83c3ea439190a 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -558,7 +558,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	WARN_ON_ONCE(IS_ENABLED(CONFIG_DEBUG_ENTRY) &&
 		     this_cpu_read(irq_count) != -1);
 
-	switch_fpu_prepare(prev_fpu, cpu);
+	if (!test_thread_flag(TIF_NEED_FPU_LOAD))
+		switch_fpu_prepare(prev_fpu, cpu);
 
 	/* We must save %fs and %gs before load_TLS() because
 	 * %fs and %gs may be cleared by load_TLS().
@@ -610,7 +611,7 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 	this_cpu_write(current_task, next_p);
 	this_cpu_write(cpu_current_top_of_stack, task_top_of_stack(next_p));
 
-	switch_fpu_finish(next_fpu, cpu);
+	switch_fpu_finish(next_fpu);
 
 	/* Reload sp0. */
 	update_task_stack(next_p);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 75301b439b6e4..4cc57223893c5 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7734,6 +7734,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		wait_lapic_expire(vcpu);
 	guest_enter_irqoff();
 
+	fpregs_assert_state_consistent();
+	if (test_thread_flag(TIF_NEED_FPU_LOAD))
+		switch_fpu_return();
+
 	if (unlikely(vcpu->arch.switch_db_regs)) {
 		set_debugreg(0, 7);
 		set_debugreg(vcpu->arch.eff_db[0], 0);
@@ -7993,22 +7997,29 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
 /* Swap (qemu) user FPU context for the guest FPU context. */
 static void kvm_load_guest_fpu(struct kvm_vcpu *vcpu)
 {
-	preempt_disable();
+	__fpregs_changes_begin();
+
 	copy_fpregs_to_fpstate(&vcpu->arch.user_fpu);
+
 	/* PKRU is separately restored in kvm_x86_ops->run.  */
 	__copy_kernel_to_fpregs(&vcpu->arch.guest_fpu.state,
 				~XFEATURE_MASK_PKRU);
-	preempt_enable();
+
+	fpregs_mark_activate();
+	__fpregs_changes_end();
 	trace_kvm_fpu(1);
 }
 
 /* When vcpu_run ends, restore user space FPU context. */
 static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
 {
-	preempt_disable();
+	__fpregs_changes_begin();
+
 	copy_fpregs_to_fpstate(&vcpu->arch.guest_fpu);
 	copy_kernel_to_fpregs(&vcpu->arch.user_fpu.state);
-	preempt_enable();
+
+	fpregs_mark_activate();
+	__fpregs_changes_end();
 	++vcpu->stat.fpu_reload;
 	trace_kvm_fpu(0);
 }
-- 
2.20.0.rc1

Re: [PATCH 29/29] x86/fpu: Defer FPU state load until return to userspace

[Sebastian Andrzej Siewior]

On 2018-11-28 23:20:35 [+0100], To linux-kernel@vger.kernel.org wrote:
> diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
> index fb16d0da71bca..f552b1d6c6958 100644
> --- a/arch/x86/kernel/fpu/signal.c
> +++ b/arch/x86/kernel/fpu/signal.c
> @@ -292,43 +295,51 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
>  		u64 init_bv = xfeatures_mask & ~xfeatures;
>  
>  		if (using_compacted_format()) {
> -			ret = copy_user_to_xstate(&state->xsave, buf_fx);
> +			ret = copy_user_to_xstate(&fpu->state.xsave, buf_fx);
>  		} else {
> -			ret = __copy_from_user(&state->xsave, buf_fx, state_size);
> +			ret = __copy_from_user(&fpu->state.xsave, buf_fx, state_size);
>  
>  			if (!ret && state_size > offsetof(struct xregs_state, header))
> -				ret = validate_xstate_header(&state->xsave.header);
> +				ret = validate_xstate_header(&fpu->state.xsave.header);
>  		}
>  		if (ret)
>  			goto err_out;
>  
> -		sanitize_restored_xstate(state, envp, xfeatures, fx_only);
> +		sanitize_restored_xstate(&fpu->state, envp, xfeatures, fx_only);
>  
> +		__fpregs_changes_begin();
>  		if (unlikely(init_bv))
>  			copy_kernel_to_xregs(&init_fpstate.xsave, init_bv);
> -		ret = copy_users_to_xregs(&state->xsave, xfeatures);
> +		ret = copy_users_to_xregs(&fpu->state.xsave, xfeatures);
>  
>  	} else if (use_fxsr()) {
> -		ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
> -		if (ret)
> +		ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
> +		if (ret) {
> +			err = -EFAULT;
>  			goto err_out;
> +		}
>  
> -		sanitize_restored_xstate(state, envp, xfeatures, fx_only);
> +		sanitize_restored_xstate(&fpu->state, &env, xfeatures, fx_only);

This should have remained `envp' and not become `&env'.

Sebastian

Re: [PATCH 29/29] x86/fpu: Defer FPU state load until return to userspace

[Sebastian Andrzej Siewior]

On 2018-11-28 23:20:35 [+0100], To linux-kernel@vger.kernel.org wrote:
> --- a/arch/x86/kernel/fpu/signal.c
> +++ b/arch/x86/kernel/fpu/signal.c
> @@ -228,13 +228,12 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
>  	struct task_struct *tsk = current;
>  	struct fpu *fpu = &tsk->thread.fpu;
>  	int state_size = fpu_kernel_xstate_size;
> -	union fpregs_state *state;
> -	void *tmp;
>  	struct user_i387_ia32_struct env;
>  	struct user_i387_ia32_struct *envp = NULL;
>  	int ret = 0;
>  	u64 xfeatures = 0;
>  	int fx_only = 0;
> +	int err;
>  
…
>  	} else if (use_fxsr()) {
> -		ret = __copy_from_user(&state->fxsave, buf_fx, state_size);
> -		if (ret)
> +		ret = __copy_from_user(&fpu->state.fxsave, buf_fx, state_size);
> +		if (ret) {
> +			err = -EFAULT;
>  			goto err_out;
> +		}

After reworking the series after addressing the comments for 08/29 I
noticed that `err' should have been `ret'. 

Sebastian

Re: [PATCH v5] x86: load FPU registers on return to userland

[Sebastian Andrzej Siewior]

On 2018-11-28 23:20:06 [+0100], Sebastian Andrzej Siewior wrote:
> This is a refurbished series originally started by by Rik van Riel. The

Could someone please apply patch 1 - 7?

Sebastian