Re: [PATCH 02/20] PCI: fix pci_remap_iospace() remap attribute

Luis R. Rodriguez
2017-03-17T16:28:45Z

On Fri, Mar 17, 2017 at 10:43:39AM +0000, Liviu Dudau wrote:
> On Fri, Mar 17, 2017 at 01:33:21AM +0100, Luis R. Rodriguez wrote:
> > a) should we then use a Fixes tag for this patch ?
>
> I'm not aware of issues being reported, but Lorenzo might have more info on this.

Lorenzo ? If not what exactly made you discover this ? If it is a fix, and only
ARM64 is implicated, seems like a worthy change to consider for stable for the
sake of stable ARM64 kernels. But, that would leave the PCI config space without
a simple 1 liner fix too -- so maybe its not worth it. Distributions wanting
to support ARM64 however would like to carry these changes, so some annotations
such as Fixes should help.

> > b) it does not seem clear what the semantics for pgprot_device() or even
> > pgprot_noncached(). Can you add some ?
> >
> > 8b921acfeffdb ("PCI: Add pci_remap_iospace() to map bus I/O resources")
> >
> > Also this patch claims archs can override this call alone, as its __weak.
> > So is the right thing to do to change pci_remap_iospace() to pgprot_noncached()
> > or is it for archs to add their own pci_remap_iospace()? If so why ? Without
> > proper semantics defined for these helpers this is all fuzzy.
>
> That was the initial intention, to let arches / platforms overwrite the whole
> pci_remap_iospace(). I guess the reality is that no one needs to overwrite it except
> for the AArch64 quirk, so probably easier to remove the __weak and fix the attributes for arm64.

Sounds much more reasonable to me.

Luis