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

Klara Modin
2024-05-10T19:22:34Z

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>