From 2eec73437487aa690882cafddca6e4d93df46f26 Mon Sep 17 00:00:00 2001
From: Jan Kiszka <jan.kiszka@siemens.com>
Date: Mon, 1 Nov 2010 14:01:29 +0100
Subject: [PATCH] KVM: x86: Avoid issuing wbinvd twice
Micro optimization to avoid calling wbinvd twice on the CPU that has to
emulate it. As we might be preempted between smp_call_function_many and
the local wbinvd, the cache might be filled again so that real work
could be done uselessly.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---
arch/x86/kvm/x86.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 35f82f2c66f6..c10135bc0f2f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4007,13 +4007,15 @@ int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu)
return X86EMUL_CONTINUE;
if (kvm_x86_ops->has_wbinvd_exit()) {
- preempt_disable();
+ int cpu = get_cpu();
+
+ cpumask_set_cpu(cpu, vcpu->arch.wbinvd_dirty_mask);
smp_call_function_many(vcpu->arch.wbinvd_dirty_mask,
wbinvd_ipi, NULL, 1);
- preempt_enable();
+ put_cpu();
cpumask_clear(vcpu->arch.wbinvd_dirty_mask);
- }
- wbinvd();
+ } else
+ wbinvd();
return X86EMUL_CONTINUE;
}
EXPORT_SYMBOL_GPL(kvm_emulate_wbinvd);
--
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