linux-kernel - Re: [RFC v1 05/26] x86/traps: Add #VE support for TDX guest

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Message-ID: <CALCETrWPCTmoeFBEJvw98zwNpw316Xii_16COZAWoYNC=obF+w@mail.gmail.com>
Date:   Fri, 12 Feb 2021 11:47:09 -0800
From:   Andy Lutomirski <luto@...nel.org>
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>,
        LKML <linux-kernel@...r.kernel.org>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [RFC v1 05/26] x86/traps: Add #VE support for TDX guest

On Fri, Feb 5, 2021 at 3:39 PM Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:
>
> From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
>
> The TDX module injects #VE exception to the guest TD in cases of
> disallowed instructions, disallowed MSR accesses and subset of CPUID
> leaves. Also, it's theoretically possible for CPU to inject #VE
> exception on EPT violation, but the TDX module makes sure this does
> not happen, as long as all memory used is properly accepted using
> TDCALLs.

By my very cursory reading of the TDX arch specification 9.8.2,
"Secure" EPT violations don't send #VE.  But the docs are quite
unclear, or at least the docs I found are.  What happens if the guest
attempts to access a secure GPA that is not ACCEPTed?  For example,
suppose the VMM does THH.MEM.PAGE.REMOVE on a secure address and the
guest accesses it, via instruction fetch or data access.  What
happens?