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

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Date:   Fri, 12 Feb 2021 11:20:14 -0800
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>
Cc:     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>,
        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 2/5/21 3:38 PM, Kuppuswamy Sathyanarayanan wrote:
> More details on cases where #VE exceptions are allowed/not-allowed:
> 
> The #VE exception do not occur in the paranoid entry paths, like NMIs.
> While other operations during an NMI might cause #VE, these are in the
> NMI code that can handle nesting, so there is no concern about
> reentrancy. This is similar to how #PF is handled in NMIs.
> 
> The #VE exception also cannot happen in entry/exit code with the
> wrong gs, such as the SWAPGS code, so it's entry point does not
> need "paranoid" handling.

Considering:

https://lore.kernel.org/lkml/20200825171903.GA20660@sjchrist-ice/

I would suggest revisiting this part of the changelog.