On Sat, 20 Jun 2020 09:46:00 +0200
Kjeld Borch Egevang <kjeld.egev...@intel.com> wrote:
> Hi VFIO users,
>
> I am working with a PCIe card that supports up to 255 VFs. In order to
> get the SR-IOV stuff to work I added some of the latest patches to the
> vfio-pci driver.
>
> I have two servers.
>
> The first one is a Centos 8 based system with many cores and a Xeon E5
> CPU. I enable VFIO with:
>
> insmod /lib/modules/$(uname -r)/kernel/drivers/vfio/vfio.ko.xz
> insmod /lib/modules/$(uname -r)/kernel/drivers/vfio/vfio_iommu_type1.ko.xz
> insmod /lib/modules/$(uname -r)/kernel/drivers/vfio/vfio_virqfd.ko.xz
> insmod /root/vfio-pci.ko enable_sriov=1 # The patched module
> echo "$vendor $device" > /sys/bus/pci/drivers/vfio-pci/new_id
> echo 15 > /sys/bus/pci/drivers/vfio-pci/*/sriov_numvfs
>
> This works and I get a PF and 15 fully functional VFs.
>
> My other server is also a Centos 8 based system but with an i7 CPU. The
> motherboard is an Asrock Z370M Pro 4.
>
> When I enable VFIO only the PF and the first 7 VFs are fully functional.
> If I enter "lspci -s 01:00.1 -x" I get a nice dump of the config space
> for VF0. But if I enter "lspci -s 01:01.0 -x" I get:
>
> 00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> 10: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> 20: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> 30: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>
> My guess is that this is either due to a limitation in the PCI bridge or
> a driver issue. What is causing this problem?
There might be an SR-IOV option in the BIOS that should be turned on,
but in general I'd expect consumer boards are pretty bad about
allocating bridge resources for SR-IOV. This might be all that the
system can support under minimum apertures. Add the following to the
kernel command line to have Linux do the SR-IOV allocation itself:
pci=realloc,assign-busses
Thanks,
Alex
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