From 3cded41794818d788aa1dc028ede4a1c1222d937 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 15 Nov 2016 16:47:06 +0100 Subject: x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted() Avoid the pointless function call to pv_lock_ops.vcpu_is_preempted() when a paravirt spinlock enabled kernel is ran on native hardware. Do this by patching out the CALL instruction with "XOR %RAX,%RAX" which has the same effect (0 return value). Signed-off-by: Peter Zijlstra (Intel) Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds Cc: Pan Xinhui Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: benh@kernel.crashing.org Cc: boqun.feng@gmail.com Cc: borntraeger@de.ibm.com Cc: bsingharora@gmail.com Cc: dave@stgolabs.net Cc: jgross@suse.com Cc: kernellwp@gmail.com Cc: konrad.wilk@oracle.com Cc: mpe@ellerman.id.au Cc: paulmck@linux.vnet.ibm.com Cc: paulus@samba.org Cc: pbonzini@redhat.com Cc: rkrcmar@redhat.com Cc: will.deacon@arm.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/kvm.c | 25 +++++++++++++------------ arch/x86/kernel/paravirt-spinlocks.c | 14 ++++++++++---- arch/x86/kernel/paravirt_patch_32.c | 8 ++++++++ arch/x86/kernel/paravirt_patch_64.c | 8 ++++++++ 4 files changed, 39 insertions(+), 16 deletions(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 0b48dd2c3554..52e90d6054fb 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -415,15 +415,6 @@ void kvm_disable_steal_time(void) wrmsr(MSR_KVM_STEAL_TIME, 0, 0); } -static bool kvm_vcpu_is_preempted(int cpu) -{ - struct kvm_steal_time *src; - - src = &per_cpu(steal_time, cpu); - - return !!src->preempted; -} - #ifdef CONFIG_SMP static void __init kvm_smp_prepare_boot_cpu(void) { @@ -480,9 +471,6 @@ void __init kvm_guest_init(void) if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) { has_steal_clock = 1; pv_time_ops.steal_clock = kvm_steal_clock; -#ifdef CONFIG_PARAVIRT_SPINLOCKS - pv_lock_ops.vcpu_is_preempted = kvm_vcpu_is_preempted; -#endif } if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) @@ -604,6 +592,14 @@ out: local_irq_restore(flags); } +__visible bool __kvm_vcpu_is_preempted(int cpu) +{ + struct kvm_steal_time *src = &per_cpu(steal_time, cpu); + + return !!src->preempted; +} +PV_CALLEE_SAVE_REGS_THUNK(__kvm_vcpu_is_preempted); + /* * Setup pv_lock_ops to exploit KVM_FEATURE_PV_UNHALT if present. */ @@ -620,6 +616,11 @@ void __init kvm_spinlock_init(void) pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock); pv_lock_ops.wait = kvm_wait; pv_lock_ops.kick = kvm_kick_cpu; + + if (kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)) { + pv_lock_ops.vcpu_is_preempted = + PV_CALLEE_SAVE(__kvm_vcpu_is_preempted); + } } static __init int kvm_spinlock_init_jump(void) diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c index 2f204dd552a4..6d4bf812af45 100644 --- a/arch/x86/kernel/paravirt-spinlocks.c +++ b/arch/x86/kernel/paravirt-spinlocks.c @@ -12,7 +12,6 @@ __visible void __native_queued_spin_unlock(struct qspinlock *lock) { native_queued_spin_unlock(lock); } - PV_CALLEE_SAVE_REGS_THUNK(__native_queued_spin_unlock); bool pv_is_native_spin_unlock(void) @@ -21,9 +20,16 @@ bool pv_is_native_spin_unlock(void) __raw_callee_save___native_queued_spin_unlock; } -static bool native_vcpu_is_preempted(int cpu) +__visible bool __native_vcpu_is_preempted(int cpu) +{ + return false; +} +PV_CALLEE_SAVE_REGS_THUNK(__native_vcpu_is_preempted); + +bool pv_is_native_vcpu_is_preempted(void) { - return 0; + return pv_lock_ops.vcpu_is_preempted.func == + __raw_callee_save___native_vcpu_is_preempted; } struct pv_lock_ops pv_lock_ops = { @@ -32,7 +38,7 @@ struct pv_lock_ops pv_lock_ops = { .queued_spin_unlock = PV_CALLEE_SAVE(__native_queued_spin_unlock), .wait = paravirt_nop, .kick = paravirt_nop, - .vcpu_is_preempted = native_vcpu_is_preempted, + .vcpu_is_preempted = PV_CALLEE_SAVE(__native_vcpu_is_preempted), #endif /* SMP */ }; EXPORT_SYMBOL(pv_lock_ops); diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c index 920c6ae08592..ff03dbd28625 100644 --- a/arch/x86/kernel/paravirt_patch_32.c +++ b/arch/x86/kernel/paravirt_patch_32.c @@ -12,6 +12,7 @@ DEF_NATIVE(pv_cpu_ops, clts, "clts"); #if defined(CONFIG_PARAVIRT_SPINLOCKS) DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%eax)"); +DEF_NATIVE(pv_lock_ops, vcpu_is_preempted, "xor %eax, %eax"); #endif unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len) @@ -27,6 +28,7 @@ unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len) } extern bool pv_is_native_spin_unlock(void); +extern bool pv_is_native_vcpu_is_preempted(void); unsigned native_patch(u8 type, u16 clobbers, void *ibuf, unsigned long addr, unsigned len) @@ -56,6 +58,12 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, end = end_pv_lock_ops_queued_spin_unlock; goto patch_site; } + case PARAVIRT_PATCH(pv_lock_ops.vcpu_is_preempted): + if (pv_is_native_vcpu_is_preempted()) { + start = start_pv_lock_ops_vcpu_is_preempted; + end = end_pv_lock_ops_vcpu_is_preempted; + goto patch_site; + } #endif default: diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c index bb3840cedb4f..e61dd9791f4f 100644 --- a/arch/x86/kernel/paravirt_patch_64.c +++ b/arch/x86/kernel/paravirt_patch_64.c @@ -21,6 +21,7 @@ DEF_NATIVE(, mov64, "mov %rdi, %rax"); #if defined(CONFIG_PARAVIRT_SPINLOCKS) DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%rdi)"); +DEF_NATIVE(pv_lock_ops, vcpu_is_preempted, "xor %rax, %rax"); #endif unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len) @@ -36,6 +37,7 @@ unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len) } extern bool pv_is_native_spin_unlock(void); +extern bool pv_is_native_vcpu_is_preempted(void); unsigned native_patch(u8 type, u16 clobbers, void *ibuf, unsigned long addr, unsigned len) @@ -68,6 +70,12 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, end = end_pv_lock_ops_queued_spin_unlock; goto patch_site; } + case PARAVIRT_PATCH(pv_lock_ops.vcpu_is_preempted): + if (pv_is_native_vcpu_is_preempted()) { + start = start_pv_lock_ops_vcpu_is_preempted; + end = end_pv_lock_ops_vcpu_is_preempted; + goto patch_site; + } #endif default: -- cgit v1.2.3