linux-kernel - Re: [PATCH v5] x86/sev: Fix making shared pages private during kdump

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Message-ID: <20250507094211.GAaBsq8zEJMAuffwmh@fat_crate.local>
Date: Wed, 7 May 2025 11:42:11 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ashish Kalra <Ashish.Kalra@....com>
Cc: tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
	x86@...nel.org, thomas.lendacky@....com, hpa@...or.com,
	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 v5] x86/sev: Fix making shared pages private during kdump

On Tue, May 06, 2025 at 06:35:29PM +0000, 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.
> 
> The check for handling the case of GHCB contained within a huge
> page incorrectly skips a page just below the GHCB page from being
> transitioned back to private during kdump preparation.
> 
> This skipped page causes a 0x404 #VC exception when it is accessed
> later while dumping guest memory during vmcore generation via kdump.
> 
> Correct the range to be checked for GHCB contained in a huge page.
> Also ensure that the skipped huge page containing the GHCB page is
> transitioned back to private by applying the correct address mask
> later when changing GHCBs to private at end of kdump preparation.
> 
> Fixes: 3074152e56c9 ("x86/sev: Convert shared memory back to private on kexec")
> Cc: stable@...r.kernel.org
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
>  arch/x86/coco/sev/core.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)

Ok, I've pushed both patches here:

https://git.kernel.org/pub/scm/linux/kernel/git/bp/bp.git/log/?h=tip-x86-urgent-sev

Please have those who are affected by the issues test and report back.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette