| Message ID | 20200827162720.278690-2-mlevitsk@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Few nSVM bugfixes | expand |
On 27/08/20 18:27, Maxim Levitsky wrote: > However in nested_svm_vmexit we were first were setting GIF to false, > but then we overwrite this with value from the hsave area. Do you mean we are overwriting the resulting intercepts with values from the hsave area? If so, I can rewrite the commit message but the patch is good! Paolo
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index fb68467e60496..95fdf068fe4c1 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -586,7 +586,6 @@ int nested_svm_vmexit(struct vcpu_svm *svm) svm->vcpu.arch.mp_state = KVM_MP_STATE_RUNNABLE; /* Give the current vmcb to the guest */ - svm_set_gif(svm, false); nested_vmcb->save.es = vmcb->save.es; nested_vmcb->save.cs = vmcb->save.cs; @@ -632,6 +631,9 @@ int nested_svm_vmexit(struct vcpu_svm *svm) /* Restore the original control entries */ copy_vmcb_control_area(&vmcb->control, &hsave->control); + /* On vmexit the GIF is set to false */ + svm_set_gif(svm, false); + svm->vmcb->control.tsc_offset = svm->vcpu.arch.tsc_offset = svm->vcpu.arch.l1_tsc_offset;
Currently code in svm_set_nested_state copies the current vmcb control area to L1 control area (hsave->control), under assumption that it mostly reflects the defaults that kvm choose, and later qemu overrides these defaults with L2 state using standard KVM interfaces, like KVM_SET_REGS. However nested GIF (which is AMD specific thing) is by default is true, and it is copied to hsave area as such. This alone is not a big deal since on VMexit, GIF is always set to false, regardless of what it was on VM entry. However in nested_svm_vmexit we were first were setting GIF to false, but then we overwrite this with value from the hsave area. Now on normal vm entry this is not a problem, since GIF is false prior to normal vm entry, and this is the value that copied to hsave, and then restored, but this is not always the case when the nested state is loaded as explained above. Anyway to fix this issue, move svm_set_gif after we restore the L1 control state in nested_svm_vmexit, so that even with wrong GIF in the saved L1 control area, we still clear GIF as the spec says. All of this is only relevant when GIF virtualization is enabled, (otherwise nested GIF doesn't reside in the vmcb). Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com> --- arch/x86/kvm/svm/nested.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)