linux-kernel - Re: [RFC v2-fix-v4 1/1] x86/tdx: Skip WBINVD instruction for TDX guest

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Message-ID: <ffedf1d2-e5ec-e0e3-8e83-edd186231029@linux.intel.com>
Date:   Tue, 8 Jun 2021 21:27:48 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.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 Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v2-fix-v4 1/1] x86/tdx: Skip WBINVD instruction for TDX
 guest


here is no resume path.

> Host is free to go into S3 independent of any guest state.

Actually my understanding is that none of the systems which support TDX 
support S3. S3 has been deprecated for a long time.


>   A hostile
> host is free to do just enough cache management so that it can resume
> from S3 while arranging for TDX guest dirty data to be lost. Does a
> TDX guest go fatal if the cache loses power?

That would be a machine check, and yes it would be fatal.

-Andi