Re: [PATCH v7 05/12] PCI: liveupdate: Keep bus numbers constant during Live Update

[sashiko-bot@kernel.org]

> During a Live Update, preserved devices must be allowed to continue
> performing memory transactions so the kernel cannot change the fabric
> topology, including bus numbers, since that would require disabling
> and flushing any memory transactions first.
> 
> To keep bus numbers constant, always inherit the secondary and
> subordinate bus numbers assigned to bridges during scanning, instead of
> assigning new ones, if any PCI devices are being preserved. Note that
> the kernel inherits bus numbers even on bridges without any downstream
> endpoints that were preserved. This avoids accidentally assigning a
> bridge a new window that overlaps with a preserved device that is
> downstream of a different bridge.
> 
> If a bridge is scanned with a broken topology or has no bus numbers
> set during a Live Update, refuse to assign it new bus numbers and refuse
> to enumerate devices below it until the Live Update is finished. This is
> a safety measure to prevent topology conflicts.
> 
> Require that CONFIG_CARDBUS is not enabled to enable
> CONFIG_PCI_LIVEUPDATE since inheriting bus numbers on PCI-to-CardBus
> bridges requires additional work but is not a priority at the moment.
> 
> Reviewed-by: Pranjal Shrivastava <praan@google.com>
> Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
> Signed-off-by: David Matlack <dmatlack@google.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260710212616.1351130-1-dmatlack@google.com?part=5