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When a system is being suspended to RAM, the PCI devices are also
suspended and the PPC code ends up calling pseries_msi_compose_msg() and
this triggers the BUG_ON() in __pci_read_msi_msg() because the device at
this point is in reduced power state. In reduced power state, the memory
mapped registers of the PCI device are not accessible.
To replicate the bug:
1. Make sure deep sleep is selected
# cat /sys/power/mem_sleep
s2idle [deep]
2. Make sure console is not suspended (so that dmesg logs are visible)
echo N > /sys/module/printk/parameters/console_suspend
3. Suspend the system
echo mem > /sys/power/state
To fix this behaviour, read the cached msi message of the device when the
device is not in PCI_D0 power state instead of touching the hardware.
Fixes: a5f3d2c17b ("powerpc/pseries/pci: Add MSI domains")
Cc: stable@vger.kernel.org # v5.15+
Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Reviewed-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250305090237.294633-1-gautam@linux.ibm.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.