* [PATCH v3 4.4.y 1/3] x86/fpu: Remove use_eager_fpu()
[not found] <1531270120-19068-1-git-send-email-daniel.sangorrin@toshiba.co.jp>
@ 2018-07-11 0:48 ` Daniel Sangorrin
2018-10-11 15:10 ` Greg Kroah-Hartman
2018-07-11 0:48 ` [PATCH v3 4.4.y 2/3] x86/fpu: Remove struct fpu::counter Daniel Sangorrin
2018-07-11 0:48 ` [PATCH v3 4.4.y 3/3] x86/fpu: Finish excising 'eagerfpu' Daniel Sangorrin
2 siblings, 1 reply; 4+ messages in thread
From: Daniel Sangorrin @ 2018-07-11 0:48 UTC (permalink / raw)
To: stable
Cc: Andy Lutomirski, Rik van Riel, Borislav Petkov, Brian Gerst,
Dave Hansen, Denys Vlasenko, Fenghua Yu, H. Peter Anvin,
Josh Poimboeuf, Linus Torvalds, Oleg Nesterov, Peter Zijlstra,
Quentin Casasnovas, Thomas Gleixner, pbonzini, Ingo Molnar,
Herbert Xu, David S. Miller, Ingo Molnar, x86, Gleb Natapov,
Greg Kroah-Hartman, yu-cheng yu, Kees Cook, Eric Biggers,
linux-crypto, linux-kernel, kvm
From: Andy Lutomirski <luto@kernel.org>
commit c592b57347069abfc0dcad3b3a302cf882602597 upstream
This removes all the obvious code paths that depend on lazy FPU mode.
It shouldn't change the generated code at all.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1475627678-20788-5-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Daniel Sangorrin <daniel.sangorrin@toshiba.co.jp>
---
arch/x86/crypto/crc32c-intel_glue.c | 17 ++++-------------
arch/x86/include/asm/fpu/internal.h | 34 +--------------------------------
arch/x86/kernel/fpu/core.c | 38 +++++--------------------------------
arch/x86/kernel/fpu/signal.c | 8 +++-----
arch/x86/kvm/cpuid.c | 4 +---
arch/x86/kvm/x86.c | 10 ----------
6 files changed, 14 insertions(+), 97 deletions(-)
diff --git a/arch/x86/crypto/crc32c-intel_glue.c b/arch/x86/crypto/crc32c-intel_glue.c
index 15f5c76..d610c11 100644
--- a/arch/x86/crypto/crc32c-intel_glue.c
+++ b/arch/x86/crypto/crc32c-intel_glue.c
@@ -48,21 +48,13 @@
#ifdef CONFIG_X86_64
/*
* use carryless multiply version of crc32c when buffer
- * size is >= 512 (when eager fpu is enabled) or
- * >= 1024 (when eager fpu is disabled) to account
+ * size is >= 512 to account
* for fpu state save/restore overhead.
*/
-#define CRC32C_PCL_BREAKEVEN_EAGERFPU 512
-#define CRC32C_PCL_BREAKEVEN_NOEAGERFPU 1024
+#define CRC32C_PCL_BREAKEVEN 512
asmlinkage unsigned int crc_pcl(const u8 *buffer, int len,
unsigned int crc_init);
-static int crc32c_pcl_breakeven = CRC32C_PCL_BREAKEVEN_EAGERFPU;
-#define set_pcl_breakeven_point() \
-do { \
- if (!use_eager_fpu()) \
- crc32c_pcl_breakeven = CRC32C_PCL_BREAKEVEN_NOEAGERFPU; \
-} while (0)
#endif /* CONFIG_X86_64 */
static u32 crc32c_intel_le_hw_byte(u32 crc, unsigned char const *data, size_t length)
@@ -185,7 +177,7 @@ static int crc32c_pcl_intel_update(struct shash_desc *desc, const u8 *data,
* use faster PCL version if datasize is large enough to
* overcome kernel fpu state save/restore overhead
*/
- if (len >= crc32c_pcl_breakeven && irq_fpu_usable()) {
+ if (len >= CRC32C_PCL_BREAKEVEN && irq_fpu_usable()) {
kernel_fpu_begin();
*crcp = crc_pcl(data, len, *crcp);
kernel_fpu_end();
@@ -197,7 +189,7 @@ static int crc32c_pcl_intel_update(struct shash_desc *desc, const u8 *data,
static int __crc32c_pcl_intel_finup(u32 *crcp, const u8 *data, unsigned int len,
u8 *out)
{
- if (len >= crc32c_pcl_breakeven && irq_fpu_usable()) {
+ if (len >= CRC32C_PCL_BREAKEVEN && irq_fpu_usable()) {
kernel_fpu_begin();
*(__le32 *)out = ~cpu_to_le32(crc_pcl(data, len, *crcp));
kernel_fpu_end();
@@ -256,7 +248,6 @@ static int __init crc32c_intel_mod_init(void)
alg.update = crc32c_pcl_intel_update;
alg.finup = crc32c_pcl_intel_finup;
alg.digest = crc32c_pcl_intel_digest;
- set_pcl_breakeven_point();
}
#endif
return crypto_register_shash(&alg);
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 146d838..7796e04 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -56,11 +56,6 @@ extern u64 fpu__get_supported_xfeatures_mask(void);
/*
* FPU related CPU feature flag helper routines:
*/
-static __always_inline __pure bool use_eager_fpu(void)
-{
- return true;
-}
-
static __always_inline __pure bool use_xsaveopt(void)
{
return static_cpu_has_safe(X86_FEATURE_XSAVEOPT);
@@ -504,24 +499,6 @@ static inline int fpu_want_lazy_restore(struct fpu *fpu, unsigned int cpu)
}
-/*
- * Wrap lazy FPU TS handling in a 'hw fpregs activation/deactivation'
- * idiom, which is then paired with the sw-flag (fpregs_active) later on:
- */
-
-static inline void __fpregs_activate_hw(void)
-{
- if (!use_eager_fpu())
- clts();
-}
-
-static inline void __fpregs_deactivate_hw(void)
-{
- if (!use_eager_fpu())
- stts();
-}
-
-/* Must be paired with an 'stts' (fpregs_deactivate_hw()) after! */
static inline void __fpregs_deactivate(struct fpu *fpu)
{
WARN_ON_FPU(!fpu->fpregs_active);
@@ -530,7 +507,6 @@ static inline void __fpregs_deactivate(struct fpu *fpu)
this_cpu_write(fpu_fpregs_owner_ctx, NULL);
}
-/* Must be paired with a 'clts' (fpregs_activate_hw()) before! */
static inline void __fpregs_activate(struct fpu *fpu)
{
WARN_ON_FPU(fpu->fpregs_active);
@@ -555,22 +531,17 @@ static inline int fpregs_active(void)
}
/*
- * Encapsulate the CR0.TS handling together with the
- * software flag.
- *
* These generally need preemption protection to work,
* do try to avoid using these on their own.
*/
static inline void fpregs_activate(struct fpu *fpu)
{
- __fpregs_activate_hw();
__fpregs_activate(fpu);
}
static inline void fpregs_deactivate(struct fpu *fpu)
{
__fpregs_deactivate(fpu);
- __fpregs_deactivate_hw();
}
/*
@@ -597,8 +568,7 @@ switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
* or if the past 5 consecutive context-switches used math.
*/
fpu.preload = static_cpu_has(X86_FEATURE_FPU) &&
- new_fpu->fpstate_active &&
- (use_eager_fpu() || new_fpu->counter > 5);
+ new_fpu->fpstate_active;
if (old_fpu->fpregs_active) {
if (!copy_fpregs_to_fpstate(old_fpu))
@@ -614,8 +584,6 @@ switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
new_fpu->counter++;
__fpregs_activate(new_fpu);
prefetch(&new_fpu->state);
- } else {
- __fpregs_deactivate_hw();
}
} else {
old_fpu->counter = 0;
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 6aa0b51..b282364 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -53,27 +53,9 @@ static bool kernel_fpu_disabled(void)
return this_cpu_read(in_kernel_fpu);
}
-/*
- * Were we in an interrupt that interrupted kernel mode?
- *
- * On others, we can do a kernel_fpu_begin/end() pair *ONLY* if that
- * pair does nothing at all: the thread must not have fpu (so
- * that we don't try to save the FPU state), and TS must
- * be set (so that the clts/stts pair does nothing that is
- * visible in the interrupted kernel thread).
- *
- * Except for the eagerfpu case when we return true; in the likely case
- * the thread has FPU but we are not going to set/clear TS.
- */
static bool interrupted_kernel_fpu_idle(void)
{
- if (kernel_fpu_disabled())
- return false;
-
- if (use_eager_fpu())
- return true;
-
- return !current->thread.fpu.fpregs_active && (read_cr0() & X86_CR0_TS);
+ return !kernel_fpu_disabled();
}
/*
@@ -121,7 +103,6 @@ void __kernel_fpu_begin(void)
copy_fpregs_to_fpstate(fpu);
} else {
this_cpu_write(fpu_fpregs_owner_ctx, NULL);
- __fpregs_activate_hw();
}
}
EXPORT_SYMBOL(__kernel_fpu_begin);
@@ -132,8 +113,6 @@ void __kernel_fpu_end(void)
if (fpu->fpregs_active)
copy_kernel_to_fpregs(&fpu->state);
- else
- __fpregs_deactivate_hw();
kernel_fpu_enable();
}
@@ -194,10 +173,7 @@ void fpu__save(struct fpu *fpu)
preempt_disable();
if (fpu->fpregs_active) {
if (!copy_fpregs_to_fpstate(fpu)) {
- if (use_eager_fpu())
- copy_kernel_to_fpregs(&fpu->state);
- else
- fpregs_deactivate(fpu);
+ copy_kernel_to_fpregs(&fpu->state);
}
}
preempt_enable();
@@ -245,8 +221,7 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
* Don't let 'init optimized' areas of the XSAVE area
* leak into the child task:
*/
- if (use_eager_fpu())
- memset(&dst_fpu->state.xsave, 0, xstate_size);
+ memset(&dst_fpu->state.xsave, 0, xstate_size);
/*
* Save current FPU registers directly into the child
@@ -268,10 +243,7 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
if (!copy_fpregs_to_fpstate(dst_fpu)) {
memcpy(&src_fpu->state, &dst_fpu->state, xstate_size);
- if (use_eager_fpu())
- copy_kernel_to_fpregs(&src_fpu->state);
- else
- fpregs_deactivate(src_fpu);
+ copy_kernel_to_fpregs(&src_fpu->state);
}
preempt_enable();
}
@@ -437,7 +409,7 @@ void fpu__clear(struct fpu *fpu)
{
WARN_ON_FPU(fpu != ¤t->thread.fpu); /* Almost certainly an anomaly */
- if (!use_eager_fpu() || !static_cpu_has(X86_FEATURE_FPU)) {
+ if (!static_cpu_has(X86_FEATURE_FPU)) {
/* FPU state will be reallocated lazily at the first use. */
fpu__drop(fpu);
} else {
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 3de0771..9be3e79 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -319,11 +319,9 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
}
fpu->fpstate_active = 1;
- if (use_eager_fpu()) {
- preempt_disable();
- fpu__restore(fpu);
- preempt_enable();
- }
+ preempt_disable();
+ fpu__restore(fpu);
+ preempt_enable();
return err;
} else {
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 7b4ea5e..338d13d 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -16,7 +16,6 @@
#include <linux/module.h>
#include <linux/vmalloc.h>
#include <linux/uaccess.h>
-#include <asm/fpu/internal.h> /* For use_eager_fpu. Ugh! */
#include <asm/user.h>
#include <asm/fpu/xstate.h>
#include "cpuid.h"
@@ -104,8 +103,7 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
if (best && (best->eax & (F(XSAVES) | F(XSAVEC))))
best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
- if (use_eager_fpu())
- kvm_x86_ops->fpu_activate(vcpu);
+ kvm_x86_ops->fpu_activate(vcpu);
/*
* The existing code assumes virtual address is 48-bit in the canonical
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 660d8a0..e6ab034 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7319,16 +7319,6 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
copy_fpregs_to_fpstate(&vcpu->arch.guest_fpu);
__kernel_fpu_end();
++vcpu->stat.fpu_reload;
- /*
- * If using eager FPU mode, or if the guest is a frequent user
- * of the FPU, just leave the FPU active for next time.
- * Every 255 times fpu_counter rolls over to 0; a guest that uses
- * the FPU in bursts will revert to loading it on demand.
- */
- if (!use_eager_fpu()) {
- if (++vcpu->fpu_counter < 5)
- kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
- }
trace_kvm_fpu(0);
}
--
2.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v3 4.4.y 2/3] x86/fpu: Remove struct fpu::counter
[not found] <1531270120-19068-1-git-send-email-daniel.sangorrin@toshiba.co.jp>
2018-07-11 0:48 ` [PATCH v3 4.4.y 1/3] x86/fpu: Remove use_eager_fpu() Daniel Sangorrin
@ 2018-07-11 0:48 ` Daniel Sangorrin
2018-07-11 0:48 ` [PATCH v3 4.4.y 3/3] x86/fpu: Finish excising 'eagerfpu' Daniel Sangorrin
2 siblings, 0 replies; 4+ messages in thread
From: Daniel Sangorrin @ 2018-07-11 0:48 UTC (permalink / raw)
To: stable
Cc: Rik van Riel, Borislav Petkov, Brian Gerst, Dave Hansen,
Denys Vlasenko, Fenghua Yu, H. Peter Anvin, Josh Poimboeuf,
Linus Torvalds, Oleg Nesterov, Peter Zijlstra,
Quentin Casasnovas, Thomas Gleixner, pbonzini, Ingo Molnar,
Ingo Molnar, x86, Andy Lutomirski, Greg Kroah-Hartman,
yu-cheng yu, linux-kernel
From: Rik van Riel <riel@redhat.com>
commit 3913cc3507575273beb165a5e027a081913ed507 upstream
With the lazy FPU code gone, we no longer use the counter field
in struct fpu for anything. Get rid it.
Signed-off-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: pbonzini@redhat.com
Link: http://lkml.kernel.org/r/1475627678-20788-6-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Daniel Sangorrin <daniel.sangorrin@toshiba.co.jp>
---
arch/x86/include/asm/fpu/internal.h | 3 ---
arch/x86/include/asm/fpu/types.h | 11 -----------
arch/x86/kernel/fpu/core.c | 3 ---
3 files changed, 17 deletions(-)
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 7796e04..c8ba9b8 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -581,15 +581,12 @@ switch_fpu_prepare(struct fpu *old_fpu, struct fpu *new_fpu, int cpu)
/* Don't change CR0.TS if we just switch! */
if (fpu.preload) {
- new_fpu->counter++;
__fpregs_activate(new_fpu);
prefetch(&new_fpu->state);
}
} else {
- old_fpu->counter = 0;
old_fpu->last_cpu = -1;
if (fpu.preload) {
- new_fpu->counter++;
if (fpu_want_lazy_restore(new_fpu, cpu))
fpu.preload = 0;
else
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 1c6f6ac..dcb85a9 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -303,17 +303,6 @@ struct fpu {
unsigned char fpregs_active;
/*
- * @counter:
- *
- * This counter contains the number of consecutive context switches
- * during which the FPU stays used. If this is over a threshold, the
- * lazy FPU restore logic becomes eager, to save the trap overhead.
- * This is an unsigned char so that after 256 iterations the counter
- * wraps and the context switch behavior turns lazy again; this is to
- * deal with bursty apps that only use the FPU for a short time:
- */
- unsigned char counter;
- /*
* @state:
*
* In-memory copy of all FPU registers that we save/restore
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index b282364..b322325 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -250,7 +250,6 @@ static void fpu_copy(struct fpu *dst_fpu, struct fpu *src_fpu)
int fpu__copy(struct fpu *dst_fpu, struct fpu *src_fpu)
{
- dst_fpu->counter = 0;
dst_fpu->fpregs_active = 0;
dst_fpu->last_cpu = -1;
@@ -353,7 +352,6 @@ void fpu__restore(struct fpu *fpu)
kernel_fpu_disable();
fpregs_activate(fpu);
copy_kernel_to_fpregs(&fpu->state);
- fpu->counter++;
kernel_fpu_enable();
}
EXPORT_SYMBOL_GPL(fpu__restore);
@@ -370,7 +368,6 @@ EXPORT_SYMBOL_GPL(fpu__restore);
void fpu__drop(struct fpu *fpu)
{
preempt_disable();
- fpu->counter = 0;
if (fpu->fpregs_active) {
/* Ignore delayed exceptions from user space */
--
2.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v3 4.4.y 3/3] x86/fpu: Finish excising 'eagerfpu'
[not found] <1531270120-19068-1-git-send-email-daniel.sangorrin@toshiba.co.jp>
2018-07-11 0:48 ` [PATCH v3 4.4.y 1/3] x86/fpu: Remove use_eager_fpu() Daniel Sangorrin
2018-07-11 0:48 ` [PATCH v3 4.4.y 2/3] x86/fpu: Remove struct fpu::counter Daniel Sangorrin
@ 2018-07-11 0:48 ` Daniel Sangorrin
2 siblings, 0 replies; 4+ messages in thread
From: Daniel Sangorrin @ 2018-07-11 0:48 UTC (permalink / raw)
To: stable
Cc: Andy Lutomirski, Borislav Petkov, Brian Gerst, Dave Hansen,
Denys Vlasenko, Fenghua Yu, H. Peter Anvin, Josh Poimboeuf,
Linus Torvalds, Oleg Nesterov, Peter Zijlstra,
Quentin Casasnovas, Rik van Riel, Thomas Gleixner, Ingo Molnar,
Jonathan Corbet, Ingo Molnar, x86, Greg Kroah-Hartman,
David Woodhouse, Razvan Ghitulete, Kees Cook, Borislav Petkov,
Hugh Dickins, linux-doc, linux-kernel
From: Andy Lutomirski <luto@kernel.org>
commit e63650840e8b053aa09ad934877e87e9941ed135 upstream
Now that eagerfpu= is gone, remove it from the docs and some
comments. Also sync the changes to tools/.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/cf430dd4481d41280e93ac6cf0def1007a67fc8e.1476740397.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Daniel Sangorrin <daniel.sangorrin@toshiba.co.jp>
Conflicts:
Documentation/kernel-parameters.txt
arch/x86/include/asm/cpufeatures.h
arch/x86/mm/pkeys.c
tools/arch/x86/include/asm/cpufeatures.h
---
Documentation/kernel-parameters.txt | 6 ------
arch/x86/include/asm/cpufeature.h | 1 -
arch/x86/include/asm/fpu/types.h | 23 -----------------------
3 files changed, 30 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4df6bd7..792945c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -961,12 +961,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
See Documentation/x86/intel_mpx.txt for more
information about the feature.
- eagerfpu= [X86]
- on enable eager fpu restore
- off disable eager fpu restore
- auto selects the default scheme, which automatically
- enables eagerfpu restore for xsaveopt.
-
module.async_probe [KNL]
Enable asynchronous probe on this module.
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 232621c..ac4aa86 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -104,7 +104,6 @@
#define X86_FEATURE_EXTD_APICID ( 3*32+26) /* has extended APICID (8 bits) */
#define X86_FEATURE_AMD_DCM ( 3*32+27) /* multi-node processor */
#define X86_FEATURE_APERFMPERF ( 3*32+28) /* APERFMPERF */
-/* free, was #define X86_FEATURE_EAGER_FPU ( 3*32+29) * "eagerfpu" Non lazy FPU restore */
#define X86_FEATURE_NONSTOP_TSC_S3 ( 3*32+30) /* TSC doesn't stop in S3 state */
/* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index dcb85a9..0d81c7d 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -310,29 +310,6 @@ struct fpu {
* the registers in the FPU are more recent than this state
* copy. If the task context-switches away then they get
* saved here and represent the FPU state.
- *
- * After context switches there may be a (short) time period
- * during which the in-FPU hardware registers are unchanged
- * and still perfectly match this state, if the tasks
- * scheduled afterwards are not using the FPU.
- *
- * This is the 'lazy restore' window of optimization, which
- * we track though 'fpu_fpregs_owner_ctx' and 'fpu->last_cpu'.
- *
- * We detect whether a subsequent task uses the FPU via setting
- * CR0::TS to 1, which causes any FPU use to raise a #NM fault.
- *
- * During this window, if the task gets scheduled again, we
- * might be able to skip having to do a restore from this
- * memory buffer to the hardware registers - at the cost of
- * incurring the overhead of #NM fault traps.
- *
- * Note that on modern CPUs that support the XSAVEOPT (or other
- * optimized XSAVE instructions), we don't use #NM traps anymore,
- * as the hardware can track whether FPU registers need saving
- * or not. On such CPUs we activate the non-lazy ('eagerfpu')
- * logic, which unconditionally saves/restores all FPU state
- * across context switches. (if FPU state exists.)
*/
union fpregs_state state;
/*
--
2.1.4
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