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Date:   Thu, 23 Nov 2017 17:13:32 +0800
From:   Wanpeng Li <>
To:     Paolo Bonzini <>
Cc:     Liran Alon <>,
        "" <>,
        kvm <>,
        Radim Krčmář <>,
        Wanpeng Li <>,
        Dmitry Vyukov <>
Subject: Re: [PATCH] KVM: VMX: Fix vmx->nested freeing when no SMI handler

d2017-11-23 0:56 GMT+08:00 Paolo Bonzini <>:
> 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

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