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

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Message-ID: <877e10gc3h.fsf@vitty.brq.redhat.com>
Date:   Thu, 06 Feb 2020 13:00:02 +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:

> 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()
> return 1 and resume guest and retry this instruction. When the error causing nested_vmx_handle_enlightened_vmptrld()
> failed can't be handled, would deadloop ouucr ?

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.

-- 
Vitaly