linux-kernel - Re: [REGRESSION][BISECTED] PCI Passthrough / SR-IOV Failure on Stable Kernel ≥ v6.12.35

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Message-ID: <6294f64a-d92d-4619-aef1-a142f5e8e4a5@linux.intel.com>
Date: Tue, 22 Jul 2025 09:30:32 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Ban ZuoXiang <bbaa@...a.fun>
Cc: iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org, bbaa@...a.moe
Subject: Re: [REGRESSION][BISECTED] PCI Passthrough / SR-IOV Failure on Stable Kernel ≥ v6.12.35

On 7/21/25 17:59, Ban ZuoXiang wrote:
> Hi all,
> 
> We've identified a regression affecting PCI passthrough / SR-IOV virtualization starting from Linux v6.12.35.
> 
> A user reported that [1], beginning with this version, SR-IOV virtual functions fail to initialize properly inside the guest. The issue appears to some MMIO operations not completing correctly in the guest.
> 
>> [    2.152320] i915 0000:07:00.0: [drm]*ERROR* GT0: GUC: mmio request 0x4509: failure 306/0
>> [    2.152327] i915 0000:07:00.0: [drm]*ERROR* GuC initialization failed (-ENXIO)
>> [    2.152330] i915 0000:07:00.0: [drm]*ERROR* GT0: Failed to initialize GPU, declaring it wedged!
> Here is the|git bisect| log:
> 
>> # bad: [fbad404f04d758c52bae79ca20d0e7fe5fef91d3] Linux 6.12.37
>> # good: [e03ced99c437f4a7992b8fa3d97d598f55453fd0] Linux 6.12.33
>> git bisect start 'HEAD' 'v6.12.33'
>> # bad: [b01a29a80cca28f0c7d0864e2d62fb9616051bfc] ACPI: bus: Bail out if acpi_kobj registration fails
>> git bisect bad b01a29a80cca28f0c7d0864e2d62fb9616051bfc
>> # bad: [b01a29a80cca28f0c7d0864e2d62fb9616051bfc] ACPI: bus: Bail out if acpi_kobj registration fails
>> git bisect bad b01a29a80cca28f0c7d0864e2d62fb9616051bfc
>> # good: [35f116a4658f787bea7e82fdd23e2e9789254f5e] drm/xe: Make xe_gt_freq part of the Documentation
>> git bisect good 35f116a4658f787bea7e82fdd23e2e9789254f5e
>> # good: [261f2a655b709e59a8d759ce9fa478778d9e84f4] crypto: qat - add shutdown handler to qat_c3xxx
>> git bisect good 261f2a655b709e59a8d759ce9fa478778d9e84f4
>> # good: [4d0686b53cc9342be3f8ce06336fd5ab0d206355] ata: ahci: Disallow LPM for Asus B550-F motherboard
>> git bisect good 4d0686b53cc9342be3f8ce06336fd5ab0d206355
>> # bad: [ce4ef0274cb66a4750000f33f2d316c0dbaf4515] KVM: s390: rename PROT_NONE to PROT_TYPE_DUMMY
>> git bisect bad ce4ef0274cb66a4750000f33f2d316c0dbaf4515
>> # bad: [8d0645b59b19d97a3b7c5a3fb8dae0c89e98cde9] parisc/unaligned: Fix hex output to show 8 hex chars
>> git bisect bad 8d0645b59b19d97a3b7c5a3fb8dae0c89e98cde9
>> # good: [fed611bd8c7b76b070aa407d0c7558e20d9e1f68] f2fs: fix to do sanity check on ino and xnid
>> git bisect good fed611bd8c7b76b070aa407d0c7558e20d9e1f68
>> # good: [8a008c89e5e5c5332e4c0a33d707db9ddd529f8a] net/sched: fix use-after-free in taprio_dev_notifier
>> git bisect good 8a008c89e5e5c5332e4c0a33d707db9ddd529f8a
>> # bad: [3f2098f4fba7718eb2501207ca6e99d22427f25a] fbdev: Fix do_register_framebuffer to prevent null-ptr-deref in fb_videomode_to_var
>> git bisect bad 3f2098f4fba7718eb2501207ca6e99d22427f25a
>> # bad: [fb5873b779dd5858123c19bbd6959566771e2e83] iommu/vt-d: Restore context entry setup order for aliased devices
>> git bisect bad fb5873b779dd5858123c19bbd6959566771e2e83
>> # good: [81c64c2f84ab581d1c45dbbbca941c13128faee6] net: ftgmac100: select FIXED_PHY
>> git bisect good 81c64c2f84ab581d1c45dbbbca941c13128faee6
>> # first bad commit: [fb5873b779dd5858123c19bbd6959566771e2e83] iommu/vt-d: Restore context entry setup order for aliased devices
>>
>> commit fb5873b779dd5858123c19bbd6959566771e2e83
>> Author: Lu Baolu<baolu.lu@...ux.intel.com>
>> Date:   Tue May 20 15:58:49 2025 +0800
>>
>>      iommu/vt-d: Restore context entry setup order for aliased devices
>>      
>>      commit 320302baed05c6456164652541f23d2a96522c06 upstream.
> This commit was introduced in [2], and the issue only affects stable kernels prior to v6.15. Besides, the Ubuntu v6.14-series kernel used by Proxmox also appears to be affected [3].

Thanks for reporting. Can this issue be reproduced with the latest
mainline linux kernel? Can it work if you simply revert this commit?

Thanks,
baolu