linux-kernel - Re: [PATCH v5 07/12] x86/traps: Add #VE support for TDX guest

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Date:   Tue, 24 Aug 2021 10:36:34 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter H Anvin <hpa@...or.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>,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 07/12] x86/traps: Add #VE support for TDX guest

On 8/24/21 10:32 AM, Kuppuswamy, Sathyanarayanan wrote:
>>> +    if (fixup_exception(regs, X86_TRAP_VE, error_code, 0))
>>
>> There are exception table entries which can trigger a #VE?
> 
> It is required to handle #VE exceptions raised by unhandled MSR
> read/writes.

Is that really the *complete* set of reasons that a #VE can be triggered
from the kernel?

Just off the top of my head, I could imagine the kernel doing a
copy_{to,from}_user() which touched user-mapped MMIO causing a #VE.