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authorMarcelo Tosatti <mtosatti@redhat.com>2008-06-06 16:37:35 -0300
committerAvi Kivity <avi@qumranet.com>2008-06-24 12:16:52 +0300
commitd4acf7e7abe45457e751525a2a4d5b693dfdd597 (patch)
tree2ff1cf6f59b0591ea39c0457705188d5f46cb118
parent62786b9e81a2dbe9c073a2ade52d33a2627d6d85 (diff)
KVM: Fix race between timer migration and vcpu migration
A guest vcpu instance can be scheduled to a different physical CPU between the test for KVM_REQ_MIGRATE_TIMER and local_irq_disable(). If that happens, the timer will only be migrated to the current pCPU on the next exit, meaning that guest LAPIC timer event can be delayed until a host interrupt is triggered. Fix it by cancelling guest entry if any vcpu request is pending. This has the side effect of nicely consolidating vcpu->requests checks. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
-rw-r--r--arch/x86/kvm/x86.c15
1 files changed, 3 insertions, 12 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 00acf1301a15..b90744a1dc3a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2759,6 +2759,8 @@ again:
if (vcpu->requests) {
if (test_and_clear_bit(KVM_REQ_MIGRATE_TIMER, &vcpu->requests))
__kvm_migrate_timers(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;
@@ -2781,21 +2783,13 @@ again:
local_irq_disable();
- if (need_resched()) {
+ if (vcpu->requests || need_resched()) {
local_irq_enable();
preempt_enable();
r = 1;
goto out;
}
- if (vcpu->requests)
- if (test_bit(KVM_REQ_MMU_RELOAD, &vcpu->requests)) {
- local_irq_enable();
- preempt_enable();
- r = 1;
- goto out;
- }
-
if (signal_pending(current)) {
local_irq_enable();
preempt_enable();
@@ -2825,9 +2819,6 @@ again:
kvm_guest_enter();
- if (vcpu->requests)
- if (test_and_clear_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests))
- kvm_x86_ops->tlb_flush(vcpu);
KVMTRACE_0D(VMENTRY, vcpu, entryexit);
kvm_x86_ops->run(vcpu, kvm_run);

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