PCI: Avoid FLR for AMD FCH AHCI adapters
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>
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