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This adds the core of the QEMU VFIO-based PCI device assignment driver.
To make use of this driver, enable CONFIG_VFIO, CONFIG_VFIO_IOMMU_TYPE1,
and CONFIG_VFIO_PCI in your host Linux kernel config. Load the vfio-pci
module. To assign device 0000:05:00.0 to a guest, do the following:
for dev in $(ls /sys/bus/pci/devices/0000:05:00.0/iommu_group/devices); do
vendor=$(cat /sys/bus/pci/devices/$dev/vendor)
device=$(cat /sys/bus/pci/devices/$dev/device)
if [ -e /sys/bus/pci/devices/$dev/driver ]; then
echo $dev > /sys/bus/pci/devices/$dev/driver/unbind
fi
echo $vendor $device > /sys/bus/pci/drivers/vfio-pci/new_id
done
See Documentation/vfio.txt in the Linux kernel tree for further
description of IOMMU groups and VFIO.
Then launch qemu including the option:
-device vfio-pci,host=0000:05:00.0
Legacy PCI interrupts (INTx) currently makes use of a kludge where we
trap BAR accesses and assume the access is in response to an interrupt,
therefore de-asserting and unmasking the interrupt. It's not quite as
targetted as using the EOI for this, but it's self contained and seems
to work across all architectures. The side-effect is a significant
performance slow-down for device in INTx mode. Some devices, like
graphics cards, don't really use their interrupt, so this can be turned
off with the x-intx=off option, which disables INTx alltogether. This
should be considered an experimental option until we refine this code.
Both MSI and MSI-X are supported and avoid these issues.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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