Re: [PATCH v3 0/2] PCI: Wait after FLR for devices that don't honor Immediate Readiness

[Bjorn Helgaas]

On Sun, Oct 11, 2026 at 09:01:43PM +0200, Alexander Gruhlke wrote:
> Since v7.2, VFIO passthrough of a Samsung 990 PRO NVMe [144d:a80c] fails
> on the second VM start, and the device is inaccessible until reboot.  The
> drive advertises Immediate Readiness but returns ~0 for up to 7 ms after
> FLR, so since 10baa9b4df40 ("PCI: Drop unnecessary retries when restoring
> BARs") the config restore after FLR is lost.
> 
> Patch 1 ignores Immediate Readiness on that drive.  Firmware 8B2QJXD7
> fixes it, but the Revision ID and Subsystem ID don't change, so the
> quirk can't tell firmware versions apart.  A 990 EVO Plus [144d:a80d]
> reports the same errors [1], but it isn't confirmed to advertise
> Immediate Readiness, so it's not included.
> 
> Patch 2 is independent and keeps pci_dev_wait() from treating ~0 as
> ready with RRS Software Visibility, which also affects the Intel
> [8086:0a54] in the open d591f6804e7e regression.  Hui, Linux-Fan: testing
> patch 2 on that drive would be appreciated.
> 
> Tested on v7.2.9 (Ryzen 9 7950X, X670E): with patch 1 and drive firmware
> 1B2QJXD7, three VM starts in a row work, and every FLR reports "ready
> 0ms after FLR".  With firmware 8B2QJXD7, plain v7.2.9 works.
> 
> Patch 2 is only tested for regressions, as the drive no longer shows the
> problem: below a Root Port with RRS SV, three VM starts work and every
> FLR reports "ready 0ms after FLR".  The VF path is untested with the
> patch, but on another machine, an X550 VF below a Root Port with RRS SV
> reads ~0 from the Vendor ID and valid data from the Command register
> 100 ms after FLR.  v1's variant, which read the Command register, was
> tested against the old firmware, and the drive's Vendor ID read ~0
> while it wasn't ready.  Applies to pci/next.
> 
> Changes since v2:
> - Patch 1: add Lukas's Reviewed-by
> - Patch 2: read the Command register on VFs whose Vendor ID reads ~0
>   instead of treating them as ready (Lukas, sashiko)
> 
> v2: https://lore.kernel.org/r/20261011163249.18479-1-gruhlke@xxxxxxxxxxx
> v1: https://lore.kernel.org/r/20261010160529.27974-1-gruhlke@xxxxxxxxxxx
> 
> [1] https://bbs.archlinux.org/viewtopic.php?id=314833
> 
> Alexander Gruhlke (2):
>   PCI: Ignore Immediate Readiness on Samsung 990 PRO NVMe
>   PCI: Don't treat ~0 as ready in pci_dev_wait() with RRS SV
> 
>  drivers/pci/pci.c    | 14 ++++++++++----
>  drivers/pci/quirks.c | 11 +++++++++++
>  2 files changed, 21 insertions(+), 4 deletions(-)

Applied to pci/reset for v7.4, thank you!