linux-kernel - [PATCH v2 0/2] PCI: Protect VPD and PME accesses from power management

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Date:   Thu,  3 Aug 2023 11:12:31 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     bhelgaas@...gle.com
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        eric.auger@...hat.com
Subject: [PATCH v2 0/2] PCI: Protect VPD and PME accesses from power management

Since v5.19, vfio-pci makes use of runtime power management on devices.
This has the effect of potentially putting entire sub-hierarchies into
lower power states, which has exposed some gaps in the PCI subsystem
around power management support.

The first issue is that lspci accesses the VPD sysfs interface, which
does not provide the same power management wrappers as general config
space.

The next covers PME, where we attempt to skip devices based on their PCI
power state, but don't protect changes to that state or look at the
overall runtime power management state of the device.

This latter patch addresses the issue noted by Eric in the follow-ups to
v1 linked below.

These patches are logically independent, but only together resolve an
issue on Eric's system where a pair of endpoints bound to vfio-pci and
unused by userspace drivers trigger faults through lspci and PME
polling.  Thanks,

Alex 

v1: https://lore.kernel.org/all/20230707151044.1311544-1-alex.williamson@redhat.com/

Alex Williamson (2):
  PCI/VPD: Add runtime power management to sysfs interface
  PCI: Fix runtime PM race with PME polling

 drivers/pci/pci.c | 23 ++++++++++++++++-------
 drivers/pci/vpd.c | 34 ++++++++++++++++++++++++++++++++--
 2 files changed, 48 insertions(+), 9 deletions(-)

-- 
2.40.1