linux-kernel - Re: [PATCH v4 2/2] x86/devmem: Drop /dev/mem access for confidential guests

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Message-ID: <CAMGD6P0ORZF6Tbkuedv99jEpk+6HjG=pyqCwTHKU5dVxt+kRCQ@mail.gmail.com>
Date: Mon, 28 Apr 2025 09:30:36 -0700
From: Jianxiong Gao <jxgao@...gle.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Dan Williams <dan.j.williams@...el.com>, dave.hansen@...ux.intel.com, x86@...nel.org, 
	Kees Cook <kees@...nel.org>, Ingo Molnar <mingo@...nel.org>, Naveen N Rao <naveen@...nel.org>, 
	Vishal Annapurve <vannapurve@...gle.com>, Kirill Shutemov <kirill.shutemov@...ux.intel.com>, 
	Nikolay Borisov <nik.borisov@...e.com>, stable@...r.kernel.org, linux-coco@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] x86/devmem: Drop /dev/mem access for confidential guests

On Mon, Apr 28, 2025 at 8:53 AM Dave Hansen <dave.hansen@...el.com> wrote:
>
> Would most developers reading this know what an "SEPT violation" is or
> what its implications are?
>
> This results in an immediate exit from and termination of the TDX guest,
> right?
>
In most cases yes but it depends on the settings.

If TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE is set then the TDX guest
is terminated immediately.

Otherwise a #VE is generated for the guest to handle.

TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE is disabled by default. See [1].

[1] https://lore.kernel.org/all/20250401130205.2198253-11-xiaoyao.li@intel.com/