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[v2,0/2] intel/pinctrl: check some registers reads

Message ID 20210324154312.61878-1-roger.pau@citrix.com
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Series intel/pinctrl: check some registers reads | expand

Message

Roger Pau Monné March 24, 2021, 3:43 p.m. UTC 
Hello,

The following series adds some consistency checks to the values returned
by some of the MMIO registers of the Intel pinctrl device.

That done to avoid a crash when running as a PVH dom0. See patch #1 for
more details.

Thanks, Roger.

Roger Pau Monne (2):
  intel/pinctrl: check REVID register value for device presence
  intel/pinctrl: check capability offset is between MMIO region

 drivers/pinctrl/intel/pinctrl-intel.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

Comments

Andy Shevchenko March 24, 2021, 5:01 p.m. UTC | #1 
On Wed, Mar 24, 2021 at 04:43:11PM +0100, Roger Pau Monne wrote:

Thanks for a fix! My comments below.

> Use the value read from the REVID register in order to check for the
> presence of the device. A read of all ones is treated as if the device
> is not present, and hence probing is ended.
> 
> This fixes an issue when running as a Xen PVH dom0, where the ACPI
> DSDT table is provided unmodified to dom0 and hence contains the
> pinctrl devices, but the MMIO region(s) containing the device
> registers might not be mapped in the guest physical memory map if such
> region(s) are not exposed on a PCI device BAR or marked as reserved in
> the host memory map.

Any particular point that we can use in the Fixes tag?

...

> Suggested-by: Andy Shevchenko <andy@kernel.org>

Hmm... was it that address I have used? In any case I think my @linux.intel.com
is better.

...

>  		/* Determine community features based on the revision */
>  		value = readl(regs + REVID);
> +		if (value == ~0u)
> +			return -ENODATA;

I think -ENODEV is more appropriate here.
Also comment above should be adjusted to explain this check.
Roger Pau Monné March 25, 2021, 8:36 a.m. UTC | #2 
On Wed, Mar 24, 2021 at 07:01:18PM +0200, Andy Shevchenko wrote:
> On Wed, Mar 24, 2021 at 04:43:11PM +0100, Roger Pau Monne wrote:
> 
> Thanks for a fix! My comments below.
> 
> > Use the value read from the REVID register in order to check for the
> > presence of the device. A read of all ones is treated as if the device
> > is not present, and hence probing is ended.
> > 
> > This fixes an issue when running as a Xen PVH dom0, where the ACPI
> > DSDT table is provided unmodified to dom0 and hence contains the
> > pinctrl devices, but the MMIO region(s) containing the device
> > registers might not be mapped in the guest physical memory map if such
> > region(s) are not exposed on a PCI device BAR or marked as reserved in
> > the host memory map.
> 
> Any particular point that we can use in the Fixes tag?

Hm, I haven't seen those issues up until 91d898e51e60 ('pinctrl:
intel: Convert capability list to features'), but the device wasn't
working properly for sure, as the registers where not accessible, it
just didn't lead to a kernel crash.

> ...
> 
> > Suggested-by: Andy Shevchenko <andy@kernel.org>
> 
> Hmm... was it that address I have used? In any case I think my @linux.intel.com
> is better.

I just used the same as the one that's on the MAINTAINERS file,
because I already had that n my Cc list. I can change to the @intel
one if that's your preference.

> ...
> 
> >  		/* Determine community features based on the revision */
> >  		value = readl(regs + REVID);
> > +		if (value == ~0u)
> > +			return -ENODATA;
> 
> I think -ENODEV is more appropriate here.
> Also comment above should be adjusted to explain this check.

Right, will change and send v3.

Thanks.