Re: [PATCH] KVM: VMX: Fix vmx->nested freeing when no SMI handler

From: Wanpeng Li
Date: Thu Nov 23 2017 - 04:13:44 EST

d2017-11-23 0:56 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>:
> On 22/11/2017 10:43, Liran Alon wrote:
>>>> I think we should also set "vmx->nested.smm.vmxon = false;"
>>>> after "vmx->nested.vmxon = false;" to correctlyhandle the case
>>>> VMXOFF is executed from SMI handler. Otherwise, when SMI handler
>>>> executes RSM, we will reach vmx_pre_leave_smm() which will set
>>>> again "vmx->nested.vmxon = true;" which I think shouldn't
>>>> happen.
>>> I didn't see a real scenario for this.
>> Actually I later saw that handle_vmoff() calls
>> nested_vmx_check_permission() which indeed won't allow to continue
>> executing if running from SMI because vmx->nested.vmxon=false; and
>> therefore this will raise a #UD. So you are right. :)
> Still, not clearing the flag is wrong. free_nested is also called by
> vmx_leave_nested when the host writes 0 to MSR_IA32_FEATURE_CONTROL with

Do it in v2. :)

Wanpeng Li