* [PATCH v4 4.4 2/4] x86/fpu: Remove use_eager_fpu()
[not found] <1539673203-21068-1-git-send-email-daniel.sangorrin@toshiba.co.jp>
2018-10-16 7:00 ` [PATCH v4 4.4 1/4] KVM: x86: remove eager_fpu field of struct kvm_vcpu_arch Daniel Sangorrin
@ 2018-10-16 7:00 ` Daniel Sangorrin
2018-10-16 7:00 ` [PATCH v4 4.4 3/4] x86/fpu: Remove struct fpu::counter Daniel Sangorrin
2018-10-16 7:00 ` [PATCH v4 4.4 4/4] x86/fpu: Finish excising 'eagerfpu' Daniel Sangorrin
3 siblings, 0 replies; 4+ messages in thread
From: Daniel Sangorrin @ 2018-10-16 7:00 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, Alexey Makhalov, Matt Helsley (VMware),
Borislav Petkov, yu-cheng yu, 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 715399b..c194d57 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 ec2aedb..2ff03cc 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -57,11 +57,6 @@ 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(X86_FEATURE_XSAVEOPT);
@@ -498,24 +493,6 @@ 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);
@@ -524,7 +501,6 @@ 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);
@@ -549,22 +525,17 @@ 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();
}
/*
@@ -591,8 +562,7 @@ 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))
@@ -608,8 +578,6 @@ 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);
}
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v4 4.4 3/4] x86/fpu: Remove struct fpu::counter
[not found] <1539673203-21068-1-git-send-email-daniel.sangorrin@toshiba.co.jp>
2018-10-16 7:00 ` [PATCH v4 4.4 1/4] KVM: x86: remove eager_fpu field of struct kvm_vcpu_arch Daniel Sangorrin
2018-10-16 7:00 ` [PATCH v4 4.4 2/4] x86/fpu: Remove use_eager_fpu() Daniel Sangorrin
@ 2018-10-16 7:00 ` Daniel Sangorrin
2018-10-16 7:00 ` [PATCH v4 4.4 4/4] x86/fpu: Finish excising 'eagerfpu' Daniel Sangorrin
3 siblings, 0 replies; 4+ messages in thread
From: Daniel Sangorrin @ 2018-10-16 7:00 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, Greg Kroah-Hartman, Bo Gan, Alexey Makhalov,
Matt Helsley (VMware),
Borislav Petkov, Andy Lutomirski, 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 2ff03cc..16825dd 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -575,15 +575,12 @@ 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 */
--
2.7.4
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH v4 4.4 4/4] x86/fpu: Finish excising 'eagerfpu'
[not found] <1539673203-21068-1-git-send-email-daniel.sangorrin@toshiba.co.jp>
` (2 preceding siblings ...)
2018-10-16 7:00 ` [PATCH v4 4.4 3/4] x86/fpu: Remove struct fpu::counter Daniel Sangorrin
@ 2018-10-16 7:00 ` Daniel Sangorrin
3 siblings, 0 replies; 4+ messages in thread
From: Daniel Sangorrin @ 2018-10-16 7:00 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, Bo Gan, Matt Helsley (VMware),
Borislav Petkov, Konrad Rzeszutek Wilk, 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>
---
Documentation/kernel-parameters.txt | 5 -----
arch/x86/include/asm/cpufeatures.h | 1 -
arch/x86/include/asm/fpu/types.h | 23 -----------------------
3 files changed, 29 deletions(-)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 3fd53e1..da515c5 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -961,11 +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/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index dd2269dc..a5fa319 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.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;
/*
--
2.7.4
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