Re: [PATCH] p2sb: Don't init until unassigned resources have been assigned.

Andy Shevchenko
2024-05-10T14:50:52Z

On Thu, May 09, 2024 at 07:04:32PM +0200, Lukas Wunner wrote:
> [cc += Shin'ichiro, Klara, Andy, Danil]

Thank you!

> On Thu, May 09, 2024 at 04:49:34PM +0000, bcfradella@proton.me wrote:
> > From: Ben Fradella <bfradell@netapp.com>
> >
> > The P2SB could get an invalid BAR from the BIOS, and that won't be fixed
> > up until pcibios_assign_resources(), which is an fs_initcall().
> >
> > - Move p2sb_fs_init() to an fs_initcall_sync(). This is still early
> > enough to avoid a race with any dependent drivers.
> >
> > - Add a check for IORESOURCE_UNSET in p2sb_valid_resource() to catch
> > unset BARs going forward.
> >
> > - Return error values from p2sb_fs_init() so that the 'initcall_debug'
> > cmdline arg provides useful data.

...

> > /*
> > - * pci_rescan_remove_lock to avoid access to unhidden P2SB devices can
> > - * not be locked in sysfs pci bus rescan path because of deadlock. To
> > - * avoid the deadlock, access to P2SB devices with the lock at an early
> > - * step in kernel initialization and cache required resources. This
> > - * should happen after subsys_initcall which initializes PCI subsystem
> > - * and before device_initcall which requires P2SB resources.
> > + * pci_rescan_remove_lock() can not be locked in sysfs pci bus rescan path

PCI bus

> > + * because of deadlock. To avoid the deadlock, access P2SB devices with the lock
> > + * at an early step in kernel initialization and cache required resources.
> > + *
> > + * We want to run as early as possible. If the P2SB was assigned a bad BAR,
> > + * we'll need to wait on pcibios_assign_resources() to fix it. So, our list of
> > + * initcall dependencies looks something like this:
> > + *
> > + * ...
> > + * subsys_initcall (pci_subsys_init)
> > + * fs_initcall (pcibios_assign_resources)
> > */

This makes sense to me
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

I assume others will conduct the proper review and testing.

--
With Best Regards,
Andy Shevchenko