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Subject: Re: [PATCH v4 1/1] x86/tdx: Handle MWAIT, MONITOR and WBINVD
To:     Dave Hansen <dave.hansen@intel.com>,
        Sean Christopherson <seanjc@google.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Andi Kleen <ak@linux.intel.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Raj Ashok <ashok.raj@intel.com>, linux-kernel@vger.kernel.org
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From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
Message-ID: <ef49222a-8ffc-dacc-4f21-3bd1ef13a2ac@linux.intel.com>
Date:   Wed, 31 Mar 2021 15:28:58 -0700
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On 3/31/21 3:11 PM, Dave Hansen wrote:
> On 3/31/21 3:06 PM, Sean Christopherson wrote:
>> I've no objection to a nice message in the #VE handler.  What I'm objecting to
>> is sanity checking the CPUID model provided by the TDX module.  If we don't
>> trust the TDX module to honor the spec, then there are a huge pile of things
>> that are far higher priority than MONITOR/MWAIT.
> 
> In other words:  Don't muck with CPUID or the X86_FEATURE at all.  Don't
> check it to comply with the spec.  If something doesn't comply, we'll
> get a #VE at *SOME* point.  We don't need to do belt-and-suspenders
> programming here.
> 
> That sounds sane to me.
But I think there are cases (like MCE) where SEAM does not disable them because
there will be future support for it. We should at-least suppress such features
in kernel.
> 

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer