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Date: Fri, 10 May 2024 17:50:46 +0300
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Lukas Wunner <lukas@wunner.de>
Cc: bcfradella@proton.me, Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>,
	Klara Modin <klarasmodin@gmail.com>,
	Danil Rybakov <danilrybakov249@gmail.com>,
	Hans de Goede <hdegoede@redhat.com>,
	Ilpo =?iso-8859-1?Q?J=E4rvinen?= <ilpo.jarvinen@linux.intel.com>,
	platform-driver-x86@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ben Fradella <bfradell@netapp.com>,
	Ranjan Dutta <ranjan.dutta@intel.com>,
	Yifan2 Li <yifan2.li@intel.com>,
	Jonathan Yong <jonathan.yong@intel.com>
Subject: Re: [PATCH] p2sb: Don't init until unassigned resources have been
 assigned.
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 <Zj0CIPR5djf0-hHb@wunner.de>
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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