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

Shinichiro Kawasaki
2024-05-12T10:24:16Z

On May 10, 2024 / 21:22, Klara Modin wrote:
> On 2024-05-10 16:50, Andy Shevchenko wrote:
> > 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.
> >
>
> This patch did not introduce any new issues on my previously problematic
> system.
>
> Tested-by: Klara Modin <klarasmodin@gmail.com>

The changes look reasonable and good to me. I also confirmed that the patch
does not affect on my use case using two my test machines.

Reviewed-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>