PCI device capable of SR-IOV support is a new, still-experimental
feature with only a single working example of the Nvme device.
This patch in an attempt to fix a double-free problem when a
SR-IOV-capable Nvme device is hot-unplugged in the following scenario:
Qemu CLI:
---------
-device pcie-root-port,slot=0,id=rp0
-device nvme-subsys,id=subsys0
-device nvme,id=nvme0,bus=rp0,serial=deadbeef,subsys=subsys0,sriov_max_vfs=1,sriov_vq_flexible=2,sriov_vi_flexible=1
Guest OS:
---------
sudo nvme virt-mgmt /dev/nvme0 -c 0 -r 1 -a 1 -n 0
sudo nvme virt-mgmt /dev/nvme0 -c 0 -r 0 -a 1 -n 0
echo 1 > /sys/bus/pci/devices/0000:01:00.0/reset
sleep 1
echo 1 > /sys/bus/pci/devices/0000:01:00.0/sriov_numvfs
nvme virt-mgmt /dev/nvme0 -c 1 -r 1 -a 8 -n 1
nvme virt-mgmt /dev/nvme0 -c 1 -r 0 -a 8 -n 2
nvme virt-mgmt /dev/nvme0 -c 1 -r 0 -a 9 -n 0
sleep 2
echo 01:00.1 > /sys/bus/pci/drivers/nvme/bind
Qemu monitor:
-------------
device_del nvme0
Explanation of the problem and the proposed solution:
1) The current SR-IOV implementation assumes it’s the PhysicalFunction
that creates and deletes VirtualFunctions.
2) It’s a design decision (the Nvme device at least) for the VFs to be
of the same class as PF. Effectively, they share the dc->hotpluggable
value.
3) When a VF is created, it’s added as a child node to PF’s PCI bus
slot.
4) Monitor/device_del triggers the ACPI mechanism. The implementation is
not aware of SR/IOV and ejects PF’s PCI slot, directly unrealizing all
hot-pluggable (!acpi_pcihp_pc_no_hotplug) children nodes.
5) VFs are unrealized directly, and it doesn’t work well with (1).
SR/IOV structures are not updated, so when it’s PF’s turn to be
unrealized, it works on stale pointers to already-deleted VFs.
The proposed fix is to make the PCI ACPI code aware of SR/IOV.
Signed-off-by: Łukasz Gieryk <lukasz.gieryk@linux.intel.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
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