linux-kernel - Re: [PATCH v3 22/22] kvm: x86: Disable interception for IA32

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Date:   Tue, 4 Jan 2022 19:32:47 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Jing Liu <jing2.liu@...el.com>
Cc:     x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, corbet@....net, shuah@...nel.org,
        jun.nakajima@...el.com, kevin.tian@...el.com,
        jing2.liu@...ux.intel.com, guang.zeng@...el.com,
        wei.w.wang@...el.com, yang.zhong@...el.com
Subject: Re: [PATCH v3 22/22] kvm: x86: Disable interception for IA32_XFD on
 demand

On 12/29/21 02:04, Sean Christopherson wrote:
> 
> Speaking of nested, interception of #NM in vmx_update_exception_bitmap() is wrong
> with respect to nested guests.  Until XFD is supported for L2, which I didn't see
> in this series, #NM should not be intercepted while L2 is running.

Why wouldn't L2 support XFD, since there are no new VMCS bits?  As long 
as L0 knows what to do with XFD and XFD_ERR, it will do the right thing 
no matter if L1 or L2 is running.

Paolo