linux-kernel - Re: [PATCH] PCI/PM: Ensure power-up succeeded before restoring MMIO state

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Message-ID: <aPpZIovpDU2KU_gg@google.com>
Date: Thu, 23 Oct 2025 09:34:42 -0700
From: Brian Norris <briannorris@...omium.org>
To: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] PCI/PM: Ensure power-up succeeded before restoring MMIO
 state

On Thu, Aug 21, 2025 at 07:58:12AM -0700, Brian Norris wrote:
> From: Brian Norris <briannorris@...gle.com>
> 
> As the comments in pci_pm_thaw_noirq() suggest, pci_restore_state() may
> need to restore MSI-X state in MMIO space. This is only possible if we
> reach D0; if we failed to power up, this might produce a fatal error
> when touching memory space.
> 
> Check for errors (as the "verify" in "pci_pm_power_up_and_verify_state"
> implies), and skip restoring if it fails.
> 
> This mitigates errors seen during resume_noirq, for example, when the
> platform did not resume the link properly.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Brian Norris <briannorris@...gle.com>
> Signed-off-by: Brian Norris <briannorris@...omium.org>

Friendly ping on this one.

This bug causes quite a bit of problem for some Pixel devices, although
that's admittedly because of our own failure to resume properly in some
cases. (And we can recover later, if we don't crash here.)

I believe the patch is still a good addition for everyone, in case other
systems fall into similar error conditions.

Brian