[6.12.y regression] Regression with 58130e7ce6cb ("PCI/ERR: Ensure error recoverability at all times"): echo vfio-pci >driver_override does not work for DVB Adapter

[Salvatore Bonaccorso <carnil@debian.org>]

Control: forwarded -1 https://lore.kernel.org/regressions/177470500712.1307944.17082968691510345174@eldamar.lan

Hi,

Bernd Schumacher reported in Debian (report and report from bisection
in https://bugs.debian.org/1131025) a 6.12.y specific regression of
58130e7ce6cb ("PCI/ERR: Ensure error recoverability at all times"):

On Tue, Mar 17, 2026 at 08:18:17AM +0100, Bernd Schumacher wrote:
>    * What led up to the situation?
> I have a kvm with linux-image-6.1.0-43-amd64 running vdr and femon.
> On the host I do echovfio-pci >/sys/bus/pci/devices/0000:$PCI/driver_override.
> Then I give the DVB Adapter to the kvm.
> 
> It works, if I boot linux-image-6.12.63+deb13-amd64 on the host.
> If it works dmesg on the kvm says:
> 05:00.0 Multimedia controller: Digital Devices GmbH Octopus DVB Adapter
> dmesg:
> [    2.443770] dvbdev: DVB: registering new adapter (DDBridge)
> [    2.443772] dvbdev: DVB: registering new adapter (DDBridge)
> ...
> [    2.694180] ddbridge 0000:05:00.0: attach tuner input 0 adr 60
> [    2.694183] ddbridge 0000:05:00.0: DVB: registering adapter 0 frontend 0 (STV090x Multistandard)...
> ...
> [    2.738542] ddbridge 0000:05:00.0: attach tuner input 1 adr 63
> [    2.738545] ddbridge 0000:05:00.0: DVB: registering adapter 1 frontend 0 (STV090x Multistandard)...
> 
> 
> It does not work, if I boot linux-image-6.12.73+deb13-amd64 on thehost.
> If it does not work dmesg on th kvm says:
> [    2.413879] ddbridge 0000:05:00.0: detected Digital Devices Cine S2 V6 DVB adapter
> [    2.413901] ddbridge 0000:05:00.0: cannot read registers
> [    2.414569] ddbridge 0000:05:00.0: fail
> 
> If I run femon it says:
> femon: opening frontend failed: No such file or directory

https://bugs.debian.org/1131025#29 contains the bisect log:

| git bisect log says:
| 
| git bisect start
| # Status: warte auf guten und schlechten Commit
| # good: [567bd8cbc2fe6b28b78864cbbbc41b0d405eb83c] Linux 6.12.63
| git bisect good 567bd8cbc2fe6b28b78864cbbbc41b0d405eb83c
| # Status: warte auf schlechten Commit, 1 guter Commit bekannt
| # bad: [5fb0303f6cb6a89bcfb19bd7a68cb793c86e78b2] Linux 6.12.73
| git bisect bad 5fb0303f6cb6a89bcfb19bd7a68cb793c86e78b2
| # good: [b1dd6860167667008c3b6f27628d071dc3daaf04] smb/client: fix
| NT_STATUS_UNABLE_TO_FREE_VM value
| git bisect good b1dd6860167667008c3b6f27628d071dc3daaf04
| # good: [1baa43ebca626aa607a03b1c0023ebac5374e62d] octeontx2-af: Fix
| error handling
| git bisect good 1baa43ebca626aa607a03b1c0023ebac5374e62d
| # good: [3845bd336a406cb7c609b515e6ee4c8818053f69] net/sched: act_ife:
| convert comma to semicolon
| git bisect good 3845bd336a406cb7c609b515e6ee4c8818053f69
| # bad: [2901d799a26d949ccf648a6c176a0091a7f1c0ed] ALSA: hda/realtek:
| Fix headset mic for TongFang X6AR55xU
| git bisect bad 2901d799a26d949ccf648a6c176a0091a7f1c0ed
| # bad: [b9b97e6aeb534315f9646b2090d1a5024c6a4e82] procfs: avoid
| fetching build ID while holding VMA lock
| git bisect bad b9b97e6aeb534315f9646b2090d1a5024c6a4e82
| # good: [b8ea101959ab1a46c92be46c238283b0fe60252e] pmdomain: imx:
| gpcv2: Fix the imx8mm gpu hang due to wrong adb400 reset
| git bisect good b8ea101959ab1a46c92be46c238283b0fe60252e
| # good: [dfc3ab6bd64860f8022d69903be299d09be86e11] mm, shmem: prevent
| infinite loop on truncate race
| git bisect good dfc3ab6bd64860f8022d69903be299d09be86e11
| # bad: [9bcc47343ee0ef346aa7b2b460c8ff56bd882fe7] ublk: fix deadlock
| when reading partition table
| git bisect bad 9bcc47343ee0ef346aa7b2b460c8ff56bd882fe7
| # good: [ff48c9312d042bfbe826ca675e98acc6c623211c] KVM: Don't clobber
| irqfd routing type when deassigning irqfd
| git bisect good ff48c9312d042bfbe826ca675e98acc6c623211c
| # bad: [d288ba832d92d16f7db0f6996ffbde2e79190ffe] tools/power
| turbostat: fix GCC9 build regression
| git bisect bad d288ba832d92d16f7db0f6996ffbde2e79190ffe
| # bad: [58130e7ce6cb6e1f73221e412fef6c85ee561425] PCI/ERR: Ensure error
| recoverability at all times
| git bisect bad 58130e7ce6cb6e1f73221e412fef6c85ee561425
| # first bad commit: [58130e7ce6cb6e1f73221e412fef6c85ee561425] PCI/ERR:
| Ensure error recoverability at all times

And https://bugs.debian.org/1131025#43 confirms again the single
revert fixing the issue.

#regzbot introduced: 58130e7ce6cb6e1f73221e412fef6c85ee561425
#regzbot link: https://bugs.debian.org/1131025

Anything else we can provide to identify the issue present in 6.12.y
kernels?

Regards,
Salvatore