linux-kernel - Re: [Question] some questions about vmx

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Message-ID: <87eev6g3xd.fsf@vitty.brq.redhat.com>
Date:   Fri, 07 Feb 2020 10:08:46 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     linmiaohe <linmiaohe@...wei.com>
Cc:     "pbonzini\@redhat.com" <pbonzini@...hat.com>,
        "rkrcmar\@redhat.com" <rkrcmar@...hat.com>,
        "sean.j.christopherson\@intel.com" <sean.j.christopherson@...el.com>,
        "wanpengli\@tencent.com" <wanpengli@...cent.com>,
        "jmattson\@google.com" <jmattson@...gle.com>,
        "joro\@8bytes.org" <joro@...tes.org>,
        "tglx\@linutronix.de" <tglx@...utronix.de>,
        "mingo\@redhat.com" <mingo@...hat.com>,
        "bp\@alien8.de" <bp@...en8.de>, "hpa\@zytor.com" <hpa@...or.com>,
        "kvm\@vger.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86\@kernel.org" <x86@...nel.org>
Subject: Re: [Question] some questions about vmx

linmiaohe <linmiaohe@...wei.com> writes:

> Hi:
> Vitaly Kuznetsov <vkuznets@...hat.com> writes:
>>linmiaohe <linmiaohe@...wei.com> writes:
>>
>>> About nWMX.
>>> When nested_vmx_handle_enlightened_vmptrld() return 0, it do not 
>>> inject any exception or set rflags to Indicate VMLAUNCH instruction 
>>> failed and skip this instruction. This would cause nested_vmx_run() 
>>
>>Yes, it seems it can. 
>>
>>nested_vmx_handle_enlightened_vmptrld() has two possible places where it can fail:
>>
>>kvm_vcpu_map() -- meaning that the guest passed some invalid GPA.
>>revision id check -- meaning that the supplied eVMCS is unsupported/garbage.
>>
>>I think the right behavior would be to nested_vmx_failInvalid() in both these cases. We can also check what genuing Hyper-V does.
>>
>
> Many thanks for your reply. I think this would be a problem too. And would you like to fix this potential problem? I have no idea
> how to fix this correctly...

Yes,

let me check what happens on Hyper-V and I'll send a patch. The problem
should not be that severe as it only affect misbehaving L1 hypervisors.

-- 
Vitaly