linux-kernel - Re: [PATCH 2/2] x86/tdx: Do not allow #VE due to EPT violation on the private memory

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Message-ID: <1542cb57-7e3a-5881-a81c-031349ae8507@intel.com>
Date:   Fri, 28 Oct 2022 08:41:59 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        luto@...nel.org, peterz@...radead.org
Cc:     sathyanarayanan.kuppuswamy@...ux.intel.com, ak@...ux.intel.com,
        dan.j.williams@...el.com, david@...hat.com, hpa@...or.com,
        seanjc@...gle.com, thomas.lendacky@....com,
        elena.reshetova@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86/tdx: Do not allow #VE due to EPT violation on the
 private memory

On 10/28/22 07:12, Kirill A. Shutemov wrote:
>  arch/x86/coco/tdx/tdx.c | 49 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 49 insertions(+)

The patch is good, but I'm not crazy about the changelog or the big ol'
comment.

Really, this would do:

	/*
	 * The kernel can not handle #VE's when accessing normal kernel
	 * memory.  Ensure that no #VE will be delivered for accesses to
	 * TD-private memory.  Only VMM-shared memory (MMIO) will #VE.
	 */
	if (!(td_attr & ATTR_SEPT_VE_DISABLE))
		panic("TD misconfiguration: SEPT_VE_DISABLE attibute must be set.\n");

I'll probably trim both of them down.  If I chop out something that's
critical, let me know, otherwise let's follow up and stick all of those
details in Documentation.