linux-kernel - Re: [PATCH v8 06/11] x86/traps: Add #VE support for TDX guest

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Date:   Sat, 9 Oct 2021 11:56:35 +0800
From:   Lai Jiangshan <jiangshanlai+lkml@...il.com>
To:     Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        X86 ML <x86@...nel.org>, Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>, Deep Shah <sdeep@...are.com>,
        VMware Inc <pv-drivers@...are.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Peter H Anvin <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 06/11] x86/traps: Add #VE support for TDX guest

On Tue, Oct 5, 2021 at 10:54 AM Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com> wrote:

>
> The entry paths do not access TD-shared memory, MMIO regions or use
> those specific MSRs, instructions, CPUID leaves that might generate #VE.
> In addition, all interrupts including NMIs are blocked by the hardware
> starting with #VE delivery until TDGETVEINFO is called.  This eliminates
> the chance of a #VE during the syscall gap or paranoid entry paths and
> simplifies #VE handling.

Hello

If the reason is applied to #VE, I think it can be applied to SVM-ES's
#VC too.  (I wish the entry code for #VC to be simplified since I'm
moving some the asm entry code to C code)


And I'm sorry I haven't read all the emails.
Has the question asked by Andy Lutomirski been answered in any emails?

https://lore.kernel.org/lkml/CALCETrU9XypKbj-TrXLB3CPW6=MZ__5ifLz0ckbB=c=Myegn9Q@mail.gmail.com/

Thanks
Lai

>
> After TDGETVEINFO #VE could happen in theory (e.g. through an NMI),
> but it is expected not to happen because TDX expects NMIs not to
> trigger #VEs. Another case where they could happen is if the #VE
> exception panics, but in this case there are no guarantees on anything
> anyways.
>