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Date:   Mon, 31 Oct 2022 07:22:36 -0700
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Subject: Re: [PATCH 2/2] x86/tdx: Do not allow #VE due to EPT violation on the
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To:     Guorui Yu <GuoRui.Yu@linux.alibaba.com>,
        kirill.shutemov@linux.intel.com
Cc:     ak@linux.intel.com, bp@alien8.de, dan.j.williams@intel.com,
        david@redhat.com, elena.reshetova@intel.com, hpa@zytor.com,
        linux-kernel@vger.kernel.org, luto@kernel.org, mingo@redhat.com,
        peterz@infradead.org, sathyanarayanan.kuppuswamy@linux.intel.com,
        seanjc@google.com, tglx@linutronix.de, thomas.lendacky@amd.com,
        x86@kernel.org
References: <20221028141220.29217-3-kirill.shutemov@linux.intel.com>
 <b5d04a6c-79b4-bbdc-b613-6958d9f75d53@linux.alibaba.com>
From:   Dave Hansen <dave.hansen@intel.com>
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On 10/30/22 21:07, Guorui Yu wrote:
> We have encountered similar problems on SEV-ES, here are their fixes
> on Kernel [1] and OVMF[2].

SEV-ES and TDX are very different beasts in this area.

> Instead of enforcing the ATTR_SEPT_VE_DISABLE in TDX guest kernel, I
> think the fix should also include necessary check on the MMIO path of
> the #VE routine.

Instead?

Without ATTR_SEPT_VE_DISABLE, a #VE can occur on basically any
instruction.  We call those kinds of exceptions "paranoid entry" points.
 They need special handling like the NMI or #MC handlers.

I'd be happy to look at a patch that does the MMIO path check *and*
turns the #VE handler into a robust entry point.

Bonus points if you can do ~5 lines of C like the approach in this thread.