Re: [PATCH 20/30] KVM: SVM: preserve VGIF across VMCB switch

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On 5/29/20 8:39 AM, Paolo Bonzini wrote:
There is only one GIF flag for the whole processor, so make sure it is not clobbered
when switching to L2 (in which case we also have to include the V_GIF_ENABLE_MASK,
lest we confuse enable_gif/disable_gif/gif_set).  When going back, L1 could in
theory have entered L2 without issuing a CLGI so make sure the svm_set_gif is
done last, after svm->vmcb->control.int_ctl has been copied back from hsave.

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
  arch/x86/kvm/svm/nested.c | 6 +++++-
  1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 7e4a506828c9..6c7f0bffdf01 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -293,6 +293,7 @@ static void nested_prepare_vmcb_save(struct vcpu_svm *svm, struct vmcb *nested_v
static void nested_prepare_vmcb_control(struct vcpu_svm *svm)
  {
+	const u32 mask = V_INTR_MASKING_MASK | V_GIF_ENABLE_MASK | V_GIF_MASK;
  	if (svm->nested.ctl.nested_ctl & SVM_NESTED_CTL_NP_ENABLE)
  		nested_svm_init_mmu_context(&svm->vcpu);
@@ -308,7 +309,10 @@ static void nested_prepare_vmcb_control(struct vcpu_svm *svm)
  	svm->vmcb->control.tsc_offset = svm->vcpu.arch.tsc_offset =
  		svm->vcpu.arch.l1_tsc_offset + svm->nested.ctl.tsc_offset;
- svm->vmcb->control.int_ctl = svm->nested.ctl.int_ctl | V_INTR_MASKING_MASK;
+	svm->vmcb->control.int_ctl             =
+		(svm->nested.ctl.int_ctl & ~mask) |
+		(svm->nested.hsave->control.int_ctl & mask);


If this is the very first VMRUN, do we have any int_ctl saved in hsave ?

+
  	svm->vmcb->control.virt_ext            = svm->nested.ctl.virt_ext;
  	svm->vmcb->control.int_vector          = svm->nested.ctl.int_vector;
  	svm->vmcb->control.int_state           = svm->nested.ctl.int_state;



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