linux-kernel - Re: [PATCH v3 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD

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Message-ID: <YGJlH76t+BGrIDVc@google.com>
Date:   Mon, 29 Mar 2021 23:39:11 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Raj Ashok <ashok.raj@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD

On Mon, Mar 29, 2021, Andy Lutomirski wrote:
> 
> > On Mar 29, 2021, at 4:17 PM, Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:
> > 
> > In non-root TDX guest mode, MWAIT, MONITOR and WBINVD instructions
> > are not supported. So handle #VE due to these instructions
> > appropriately.
> 
> Is there something I missed elsewhere in the code that checks CPL?

#GP due to CPL!=0 has priority over VM-Exit, i.e. userspace will get a #GP
directly; there will be no VM-Exit to the TDX Module and thus no #VE.

SDM section "25.1.1 - Relative Priority of Faults and VM Exits".