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 ---
This is the 1st of 3 patches that I backported to remove fpu lazy mode deadcode from stable 4.4.
Important: the patch depends on commit 5a5fbdc0e3f1 ("KVM: x86: remove eager_fpu field of struct kvm_vcpu_arch"), please cherry-pick it.
While backporting there was a conflict with fpu/core.c, caused by commit bf15a8cf8d14 ("x86/fpu/xstate: Rename 'xstate_size' to 'fpu_kernel_xstate_size', to distinguish it from 'fpu_user_xstate_size'") not being in 4.4.y. I fixed that conflict manually. (Resending with all maintainers in Cc)
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); }