linux-kernel - Re: [PATCH v3] x86/sev: Do not touch VMSA pages during kdump of SNP guest memory

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Message-ID: <07a171bf-27b0-f273-b3cd-9c77f68d865f@amd.com>
Date: Tue, 29 Apr 2025 13:38:38 -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: kees@...nel.org, michael.roth@....com, nikunj@....com, seanjc@...gle.com,
 ardb@...nel.org, gustavoars@...nel.org, sgarzare@...hat.com,
 stable@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org, kexec@...ts.infradead.org,
 linux-coco@...ts.linux.dev
Subject: Re: [PATCH v3] x86/sev: Do not touch VMSA pages during kdump of SNP
 guest memory

On 4/28/25 16:41, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@....com>
> 
> When kdump is running makedumpfile to generate vmcore and dumping SNP
> guest memory it touches the VMSA page of the vCPU executing kdump which
> then results in unrecoverable #NPF/RMP faults as the VMSA page is
> marked busy/in-use when the vCPU is running and subsequently causes
> guest softlockup/hang.
> 
> Additionally other APs may be halted in guest mode and their VMSA pages
> are marked busy and touching these VMSA pages during guest memory dump
> will also cause #NPF.
> 
> Issue AP_DESTROY GHCB calls on other APs to ensure they are kicked out
> of guest mode and then clear the VMSA bit on their VMSA pages.
> 
> If the vCPU running kdump is an AP, mark it's VMSA page as offline to
> ensure that makedumpfile excludes that page while dumping guest memory.
> 
> 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 | 241 +++++++++++++++++++++++++--------------
>  1 file changed, 155 insertions(+), 86 deletions(-)
>