linux-kernel - Re: [RFC v2 16/32] x86/tdx: Handle MWAIT, MONITOR and WBINVD

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Message-ID: <f00f6e1b-f152-a51d-d8c1-612f2e81e3aa@intel.com>
Date:   Tue, 11 May 2021 08:53:24 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 16/32] x86/tdx: Handle MWAIT, MONITOR and WBINVD

On 4/26/21 11:01 AM, Kuppuswamy Sathyanarayanan wrote:
> For WBIND instruction, since it's related to memory writeback

	^ WBINVD

> and cache flushes, it's mainly used in context of IO devices. Since
> TDX 1.0 does not support non-virtual I/O devices, skipping it should
> not cause any fatal issues. But
Do me a favor:

	grep -ri wbinvd arch/x86/

How many I/O devices do you see?

Please get your ducks in a row here.  Come up with a coherent changelog
about why the arch/x86 use of WBINVD doesn't apply to TDX guests.
Explain the audit that you did.  You *DID* do an audit, right?