linux-kernel - AMD SNP guest kdump broken since linuxnext-20250908

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Message-ID: <e8ace4cc-eb22-4117-b34d-16ecc1c8742d@amd.com>
Date: Wed, 24 Sep 2025 17:35:42 +0530
From: "Aithal, Srikanth" <sraithal@....com>
To: Linux-Next Mailing List <linux-next@...r.kernel.org>, open list
	<linux-kernel@...r.kernel.org>, KVM <kvm@...r.kernel.org>
CC: "Kalra, Ashish" <Ashish.Kalra@....com>
Subject: AMD SNP guest kdump broken since linuxnext-20250908

Hello all,

kdump on an SNP guest is broken in linux-next, starting with 
next-20250908 [1].

kdump on an SNP guest works with the following kernels as the guest kernel:

 1. https://git.kernel.org/pub/scm/virt/kvm/kvm.git, kvm/next
 2. git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git,
    next-20250905
 3. git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git,
    v6.17-rc7

The crash log during kdump varies each time. I have attached all 
variants of the error console logs to this bug report as files, as they 
are too large to include here.

kdump with other guest types (normal, SEV, SEV-ES) is working fine.

I attempted bisecting multiple times, but due to varying error console 
messages—sometimes with a call trace, sometimes just a hang with no 
error messages, and sometimes with extensive register dumps including 
KVM hardware error messages—I had no success until now. Additionally, a 
couple of linux-next bisect attempt pointed to a merge commit where the 
parent commits had no issues, suggesting a possible merge problem.

I am also attaching the host kernel config and guest kernel config used 
for these tests.

Tests were conducted with the following component versions:

  * Host kernel: next-20250919
  * QEMU version: v10.1.0
  * EDK2: edk2-stable202508
  * Platform: Milan with the latest BIOS v2.20

Thank you,

Srikanth Aithal <Srikanth.Aithal@....com>

Content of type "text/html" skipped

View attachment "call_trace01.log" of type "text/plain" (5729 bytes)

View attachment "call_trace02.txt" of type "text/plain" (100271 bytes)

View attachment "call_trace03.txt" of type "text/plain" (5958 bytes)

View attachment "guest_config" of type "text/plain" (155306 bytes)

View attachment "host_config" of type "text/plain" (190043 bytes)