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From:   Wanpeng Li <kernellwp@gmail.com>
Date:   Thu, 23 Nov 2017 17:13:32 +0800
Message-ID: <CANRm+Cw7Hta7TRBZbqHkg_-UBoQYHYZoGPTEcw6TRZ2kmDcYwg@mail.gmail.com>
Subject: Re: [PATCH] KVM: VMX: Fix vmx->nested freeing when no SMI handler
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Liran Alon <LIRAN.ALON@oracle.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        kvm <kvm@vger.kernel.org>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Wanpeng Li <wanpeng.li@hotmail.com>,
        Dmitry Vyukov <dvyukov@google.com>
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d2017-11-23 0:56 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
> 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
> KVM_SET_MSRS.

Do it in v2. :)

Regards,
Wanpeng Li

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