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locking/core, x86/paravirt: Implement vcpu_is_preempted(cpu) for KVM and Xen guests 

Optimize spinlock and mutex busy-loops by providing a vcpu_is_preempted(cpu)
function on KVM and Xen platforms.

Extend the pv_lock_ops interface accordingly and implement the callbacks
on KVM and Xen.

Signed-off-by: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
[ Translated to English. ]
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: David.Laight@ACULAB.COM
Cc: Linus Torvalds <torvalds@linux-foundation.org>
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: linuxppc-dev@lists.ozlabs.org
Cc: mpe@ellerman.id.au
Cc: paulmck@linux.vnet.ibm.com
Cc: paulus@samba.org
Cc: rkrcmar@redhat.com
Cc: virtualization@lists.linux-foundation.org
Cc: will.deacon@arm.com
Cc: xen-devel-request@lists.xenproject.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/1478077718-37424-7-git-send-email-xinhui.pan@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Pan Xinhui 2016-11-02 05:08:33 -04:00 committed by Ingo Molnar
parent 760928c0da
commit 446f3dc8cc
3 changed files with 16 additions and 0 deletions
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2
arch/x86/include/asm/paravirt_types.h
View File

@ -310,6 +310,8 @@ struct pv_lock_ops {
void (*wait)(u8 *ptr, u8 val);
void (*kick)(int cpu);
bool (*vcpu_is_preempted)(int cpu);
};
/* This contains all the paravirt structures: we get a convenient

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

@ -26,6 +26,14 @@
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>
/*

6
arch/x86/kernel/paravirt-spinlocks.c
View File

@ -21,12 +21,18 @@ bool pv_is_native_spin_unlock(void)
__raw_callee_save___native_queued_spin_unlock;
}
static bool native_vcpu_is_preempted(int cpu)
{
return 0;
}
struct pv_lock_ops pv_lock_ops = {
#ifdef CONFIG_SMP
.queued_spin_lock_slowpath = native_queued_spin_lock_slowpath,
.queued_spin_unlock = PV_CALLEE_SAVE(__native_queued_spin_unlock),
.wait = paravirt_nop,
.kick = paravirt_nop,
.vcpu_is_preempted = native_vcpu_is_preempted,
#endif /* SMP */
};
EXPORT_SYMBOL(pv_lock_ops);