linux-kernel - Re: [PATCH v1 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD

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Message-Id: <91C0F6F1-B8C3-4130-B903-C63CD4B87F3F@amacapital.net>
Date:   Sat, 27 Mar 2021 09:03:36 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     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>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD




> On Mar 26, 2021, at 8:40 PM, Kuppuswamy, Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:
> 
> 
> 
> On 3/26/21 7:40 PM, Andy Lutomirski wrote:
>>>> On Mar 26, 2021, at 5:18 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 as no ops.
>> These should at least be WARN.
> I will change it to WARN.
>> Does TDX send #UD if these instructions have the wrong CPL?  
> No, TDX does not trigger #UD for these instructions.
> If the #VE came from user mode, we should send an appropriate signal instead.
> It will be mapped into #GP(0) fault. This should be enough notification right?

Yes. And I did mean #GP, not #UD.