linux-kernel - [PATCH] kvm/x86: check KVM_REQ_TLB

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Date:	Mon, 16 Mar 2009 14:03:45 +0100
From:	Joerg Roedel <joerg.roedel@....com>
To:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>
CC:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Joerg Roedel <joerg.roedel@....com>
Subject: [PATCH] kvm/x86: check KVM_REQ_TLB_FLUSH with irqs disabled

For KVM remote TLB flushes we need to check the KVM_REQ_TLB_FLUSH
request flag when the irqs are already disabled. Otherwise there is a
small window of time for a race condition where we may enter a guest
without doing a requested TLB flush.

Signed-off-by: Joerg Roedel <joerg.roedel@....com>
---
 arch/x86/kvm/x86.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b556b6a..301660a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3108,8 +3108,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 			kvm_write_guest_time(vcpu);
 		if (test_and_clear_bit(KVM_REQ_MMU_SYNC, &vcpu->requests))
 			kvm_mmu_sync_roots(vcpu);
-		if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests))
-			kvm_x86_ops->tlb_flush(vcpu);
 		if (test_and_clear_bit(KVM_REQ_REPORT_TPR_ACCESS,
 				       &vcpu->requests)) {
 			kvm_run->exit_reason = KVM_EXIT_TPR_ACCESS;
@@ -3133,6 +3131,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 
 	local_irq_disable();
 
+	if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests))
+		kvm_x86_ops->tlb_flush(vcpu);
+
 	if (vcpu->requests || need_resched() || signal_pending(current)) {
 		local_irq_enable();
 		preempt_enable();
-- 
1.5.6.4


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