From: Vasant Hegde <vasant.hegde@amd.com>
To: Ashish Kalra <Ashish.Kalra@amd.com>,
joro@8bytes.org, suravee.suthikulpanit@amd.com,
thomas.lendacky@amd.com, Sairaj.ArunKodilkar@amd.com,
herbert@gondor.apana.org.au
Cc: seanjc@google.com, pbonzini@redhat.com, will@kernel.org,
robin.murphy@arm.com, john.allen@amd.com, davem@davemloft.net,
michael.roth@amd.com, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
kvm@vger.kernel.org
Subject: Re: [PATCH v5 4/4] iommu/amd: Skip enabling command/event buffers for kdump
Date: Thu, 21 Aug 2025 17:02:17 +0530 [thread overview]
Message-ID: <7deb2d90-8a42-480b-b4e2-f784927160f8@amd.com> (raw)
In-Reply-To: <e66b75e126fa245e126fe81ed73baffdf603369a.1753911773.git.ashish.kalra@amd.com>
On 7/31/2025 3:26 AM, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@amd.com>
>
> After a panic if SNP is enabled in the previous kernel then the kdump
> kernel boots with IOMMU SNP enforcement still enabled.
>
> IOMMU command buffers and event buffer registers remain locked and
> exclusive to the previous kernel. Attempts to enable command and event
> buffers in the kdump kernel will fail, as hardware ignores writes to
> the locked MMIO registers as per AMD IOMMU spec Section 2.12.2.1.
>
> Skip enabling command buffers and event buffers for kdump boot as they
> are already enabled in the previous kernel.
>
> Tested-by: Sairaj Kodilkar <sarunkod@amd.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
-Vasant
prev parent reply other threads:[~2025-08-21 11:32 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-30 21:55 [PATCH v5 0/4] Add host kdump support for SNP Ashish Kalra
2025-07-30 21:55 ` [PATCH v5 1/4] iommu/amd: Add support to remap/unmap IOMMU buffers for kdump Ashish Kalra
2025-08-21 11:29 ` Vasant Hegde
2025-07-30 21:56 ` [PATCH v5 2/4] iommu/amd: Reuse device table " Ashish Kalra
2025-08-21 11:45 ` Vasant Hegde
2025-07-30 21:56 ` [PATCH v5 3/4] crypto: ccp: Skip SEV and SNP INIT for kdump boot Ashish Kalra
2025-08-22 16:48 ` Tom Lendacky
2025-07-30 21:56 ` [PATCH v5 4/4] iommu/amd: Skip enabling command/event buffers for kdump Ashish Kalra
2025-08-21 11:32 ` Vasant Hegde [this message]
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