691a8e26de
commit 63ba51db24ed1b8f8088a897290eb6c036c5435d upstream. PCI passthrough to VMs does not work with AMD FCH AHCI adapters: the guest OS fails to correctly probe devices attached to the controller due to FIS communication failures: ata4: softreset failed (1st FIS failed) ... ata4.00: qc timeout after 5000 msecs (cmd 0xec) ata4.00: failed to IDENTIFY (I/O error, err_mask=0x4) Forcing the "bus" reset method before unbinding & binding the adapter to the vfio-pci driver solves this issue, e.g.: echo "bus" > /sys/bus/pci/devices/<ID>/reset_method gives a working guest OS, indicating that the default FLR reset method doesn't work correctly. Apply quirk_no_flr() to AMD FCH AHCI devices to work around this issue. Link: https://lore.kernel.org/r/20230128013951.523247-1-damien.lemoal@opensource.wdc.com Reported-by: Niklas Cassel <niklas.cassel@wdc.com> Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 Restructured Text 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.