[patch 32/45] KVM guest: do not batch pte updates from interrupt context

[Greg KH]

2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

commit 6ba661787594868512a71c129062ebd57d0c01e7 upstream.

Commit b8bcfe997e4 made paravirt pte updates synchronous in interrupt
context.

Unfortunately the KVM pv mmu code caches the lazy/nonlazy mode
internally, so a pte update from interrupt context during a lazy mmu
operation can be batched while it should be performed synchronously.

https://bugzilla.redhat.com/show_bug.cgi?id=518022

Drop the internal mode variable and use paravirt_get_lazy_mode(), which
returns the correct state.

Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/x86/kernel/kvm.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -34,7 +34,6 @@
 struct kvm_para_state {
 	u8 mmu_queue[MMU_QUEUE_SIZE];
 	int mmu_queue_len;
-	enum paravirt_lazy_mode mode;
 };
 
 static DEFINE_PER_CPU(struct kvm_para_state, para_state);
@@ -77,7 +76,7 @@ static void kvm_deferred_mmu_op(void *bu
 {
 	struct kvm_para_state *state = kvm_para_state();
 
-	if (state->mode != PARAVIRT_LAZY_MMU) {
+	if (paravirt_get_lazy_mode() != PARAVIRT_LAZY_MMU) {
 		kvm_mmu_op(buffer, len);
 		return;
 	}
@@ -185,10 +184,7 @@ static void kvm_release_pt(unsigned long
 
 static void kvm_enter_lazy_mmu(void)
 {
-	struct kvm_para_state *state = kvm_para_state();
-
 	paravirt_enter_lazy_mmu();
-	state->mode = paravirt_get_lazy_mode();
 }
 
 static void kvm_leave_lazy_mmu(void)
@@ -197,7 +193,6 @@ static void kvm_leave_lazy_mmu(void)
 
 	mmu_queue_flush(state);
 	paravirt_leave_lazy_mmu();
-	state->mode = paravirt_get_lazy_mode();
 }
 
 static void __init paravirt_ops_setup(void)


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