linux-kernel - Re: [PATCH v2] x86/sev: Fix making shared pages private during kdump

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Message-ID: <b7a8dce0-96b6-295b-d2c2-3d4439181488@amd.com>
Date: Tue, 29 Apr 2025 13:44:36 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Ashish Kalra <Ashish.Kalra@....com>, tglx@...utronix.de,
 mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org, bp@...en8.de,
 hpa@...or.com
Cc: michael.roth@....com, nikunj@....com, seanjc@...gle.com, ardb@...nel.org,
 stable@...r.kernel.org, linux-kernel@...r.kernel.org,
 kexec@...ts.infradead.org, linux-coco@...ts.linux.dev
Subject: Re: [PATCH v2] x86/sev: Fix making shared pages private during kdump

On 4/28/25 14:26, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@....com>
> 
> When the shared pages are being made private during kdump preparation
> there are additional checks to handle shared GHCB pages.
> 
> These additional checks include handling the case of GHCB page being
> contained within a huge page.
> 
> There is a bug in this additional check for GHCB page contained
> within a huge page which causes any shared page just below the
> per-cpu GHCB getting skipped from being transitioned back to private
> before kdump preparation which subsequently causes a 0x404 #VC
> exception when this shared page is accessed later while dumping guest
> memory during vmcore generation via kdump.
> 
> Correct the detection and handling of GHCB pages contained within
> a huge page.
> 
> Cc: stable@...r.kernel.org
> Fixes: 3074152e56c9 ("x86/sev: Convert shared memory back to private on kexec")
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>

Reviewed-by: Tom Lendacky <thomas.lendacky@....com>

> ---
>  arch/x86/coco/sev/core.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
>