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

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Message-ID: <20210407152417.GM1285835@tassilo.jf.intel.com>
Date:   Wed, 7 Apr 2021 08:24:17 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andy Lutomirski <luto@...nel.org>,
        "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...el.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>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD

> Hmm, I forgot about that quirk.  I would expect the TDX Module to inject a #GP
> for that case.  I can't find anything in the spec that confirms or denies that,
> but injecting #VE would be weird and pointless.
> 
> Andi/Sathya, the TDX Module spec should be updated to state that XSETBV will
> #GP at CPL!=0.  If that's not already the behavior, the module should probably
> be changed...

I asked about this and the answer was that XSETBV behaves architecturally inside
a TD (no #VE), thus there is nothing to document.

-Andi