[PATCH] KVM: MMU: make kvm_mmu_reset_context() flush the guest TLB

[PATCH] KVM: MMU: make kvm_mmu_reset_context() flush the guest TLB

[Avi Kivity]

kvm_set_cr0() and kvm_set_cr4(), and possible other functions,
assume that kvm_mmu_reset_context() flushes the guest TLB.  However,
it does not.

Fix by flushing the tlb (and syncing the new root as well).

Signed-off-by: Avi Kivity <avi@redhat.com>
---
 arch/x86/kvm/mmu.c |   12 +++++++++++-
 1 files changed, 11 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 19ebb76..b439ab7 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3042,8 +3042,18 @@ static void destroy_kvm_mmu(struct kvm_vcpu *vcpu)
 
 int kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
 {
+	int r;
+
 	destroy_kvm_mmu(vcpu);
-	return init_kvm_mmu(vcpu);
+	r = init_kvm_mmu(vcpu);
+
+	if (r)
+		goto err;
+
+	kvm_mmu_sync_roots(vcpu);
+	kvm_mmu_flush_tlb(vcpu);
+err:
+	return r;
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_reset_context);
 
-- 
1.7.5.3

Re: [PATCH] KVM: MMU: make kvm_mmu_reset_context() flush the guest TLB

[Marcelo Tosatti]

On Sun, Jun 12, 2011 at 06:25:00PM +0300, Avi Kivity wrote:
> kvm_set_cr0() and kvm_set_cr4(), and possible other functions,
> assume that kvm_mmu_reset_context() flushes the guest TLB.  However,
> it does not.

TLB flush should be done lazily during guest entry, in
kvm_mmu_load(). Don't see why this patch is needed.

> 
> Fix by flushing the tlb (and syncing the new root as well).
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>

Re: [PATCH] KVM: MMU: make kvm_mmu_reset_context() flush the guest TLB

[Avi Kivity]

On 06/20/2011 09:32 PM, Marcelo Tosatti wrote:
> On Sun, Jun 12, 2011 at 06:25:00PM +0300, Avi Kivity wrote:
> >  kvm_set_cr0() and kvm_set_cr4(), and possible other functions,
> >  assume that kvm_mmu_reset_context() flushes the guest TLB.  However,
> >  it does not.
>
> TLB flush should be done lazily during guest entry, in
> kvm_mmu_load(). Don't see why this patch is needed.

You're right.  It should be reverted.

-- 
error compiling committee.c: too many arguments to function