Re: [PATCH v3 3/8] PCI: Restore resource alignment

[Bjorn Helgaas]

On Thu, Aug 08, 2024 at 04:28:50PM -0400, Stewart Hildebrand wrote:
> On 8/8/24 15:28, Bjorn Helgaas wrote:
> > On Wed, Aug 07, 2024 at 11:17:12AM -0400, Stewart Hildebrand wrote:
> >> Devices with alignment specified will lose their alignment in cases when
> >> the bridge resources have been released, e.g. due to insufficient bridge
> >> window size. Restore the alignment.
> > 
> > I guess this fixes a problem when the user has specified
> > "pci=resource_alignment=..." and we've decided to release and
> > reallocate a bridge window?  Just looking for a bit more concrete
> > description of what this problem would look like to a user.
> 
> Yes. When alignment has been specified via pcibios_default_alignment()
> or by the user with "pci=resource_alignment=...", and the bridge window
> is being reallocated, the specified alignment is lost and the resource
> may not be sufficiently aligned after reallocation.
> 
> I can expand the commit description.

I think a hint about where the alignment gets lost would be helpful,
too.

This seems like a problem users could be seeing today, even
independent of the device passthrough issue that I think is the main
thrust of this series.  If there's a problem report or an easy way to
reproduce this problem, that would be nice, too.

Bjorn