Re: [PATCH v10 06/13] PCI: liveupdate: Preserve bus numbers during Live Update

[sashiko-bot@kernel.org]

> Keep the secondary and subordinate bus numbers that the previous kernel
> programmed into bridges, rather than assigning new ones, if the previous
> kernel preserved any device across a Live Update. Do this even on
> architectures that would otherwise always assign bus numbers themselves,
> e.g. when pci=assign-busses is passed.
> 
> Preserved devices must be allowed to continue performing memory
> transactions across a Live Update, so the kernel cannot change the
> fabric topology. Changing the bus numbers of a bridge changes the
> RequesterIDs of the devices below it, which would require disabling and
> flushing any in-flight memory transactions first.
> 
> Apply the policy globally rather than only to the paths that contain
> preserved devices. Bus numbers have to be preserved above a preserved
> device anyway, since an upstream bridge cannot expand its window. A
> [ ... ]
> Require that CONFIG_CARDBUS is not enabled to enable
> CONFIG_PCI_LIVEUPDATE since preserving bus numbers on PCI-to-CardBus
> bridges requires additional work but is not a priority at the moment.
> 
> Signed-off-by: David Matlack <dmatlack@google.com>

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

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