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x86/paravirt: Optimize native pv_lock_ops.vcpu_is_preempted()

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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) <peterz@infradead.org>
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2016-11-15 16:47:06 +01:00 committed by Ingo Molnar
parent 05ffc95139
commit 3cded41794
9 changed files with 54 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/x86/include/asm/paravirt.h
View File

@ -678,6 +678,11 @@ static __always_inline void pv_kick(int cpu)
PVOP_VCALL1(pv_lock_ops.kick, cpu);
}
static __always_inline bool pv_vcpu_is_preempted(int cpu)
{
return PVOP_CALLEE1(bool, pv_lock_ops.vcpu_is_preempted, cpu);
}
#endif /* SMP && PARAVIRT_SPINLOCKS */
#ifdef CONFIG_X86_32

2
arch/x86/include/asm/paravirt_types.h
View File

@ -311,7 +311,7 @@ struct pv_lock_ops {
void (*wait)(u8 *ptr, u8 val);
void (*kick)(int cpu);
bool (*vcpu_is_preempted)(int cpu);
struct paravirt_callee_save vcpu_is_preempted;
};
/* This contains all the paravirt structures: we get a convenient

6
arch/x86/include/asm/qspinlock.h
View File

@ -32,6 +32,12 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
{
pv_queued_spin_unlock(lock);
}
#define vcpu_is_preempted vcpu_is_preempted
static inline bool vcpu_is_preempted(int cpu)
{
return pv_vcpu_is_preempted(cpu);
}
#else
static inline void queued_spin_unlock(struct qspinlock *lock)
{

8
arch/x86/include/asm/spinlock.h
View File

@ -26,14 +26,6 @@
extern struct static_key paravirt_ticketlocks_enabled;
static __always_inline bool static_key_false(struct static_key *key);
#ifdef CONFIG_PARAVIRT_SPINLOCKS
#define vcpu_is_preempted vcpu_is_preempted
static inline bool vcpu_is_preempted(int cpu)
{
return pv_lock_ops.vcpu_is_preempted(cpu);
}
#endif
#include <asm/qspinlock.h>
/*

25
arch/x86/kernel/kvm.c
View File

@ -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 @@ static void kvm_wait(u8 *ptr, u8 val)
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)

14
arch/x86/kernel/paravirt-spinlocks.c
View File

@ -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 0;
return false;
}
PV_CALLEE_SAVE_REGS_THUNK(__native_vcpu_is_preempted);
bool pv_is_native_vcpu_is_preempted(void)
{
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);

8
arch/x86/kernel/paravirt_patch_32.c
View File

@ -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:

8
arch/x86/kernel/paravirt_patch_64.c
View File

@ -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:

5
arch/x86/xen/spinlock.c
View File

@ -114,6 +114,8 @@ void xen_uninit_lock_cpu(int cpu)
per_cpu(irq_name, cpu) = NULL;
}
PV_CALLEE_SAVE_REGS_THUNK(xen_vcpu_stolen);
/*
* Our init of PV spinlocks is split in two init functions due to us
* using paravirt patching and jump labels patching and having to do
@ -136,8 +138,7 @@ void __init xen_init_spinlocks(void)
pv_lock_ops.queued_spin_unlock = PV_CALLEE_SAVE(__pv_queued_spin_unlock);
pv_lock_ops.wait = xen_qlock_wait;
pv_lock_ops.kick = xen_qlock_kick;
pv_lock_ops.vcpu_is_preempted = xen_vcpu_stolen;
pv_lock_ops.vcpu_is_preempted = PV_CALLEE_SAVE(xen_vcpu_stolen);
}
/*