On 11/13/2014 02:04 AM, Sathya Perla wrote:
-----Original Message-----
From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx]
On Tue, 2014-11-11 at 14:09 -0500, Don Dutile wrote:
On 11/10/2014 06:53 AM, Sathya Perla wrote:
A user must not be allowed to disable VFs while they are already assigned
to
a guest. This check is being made in each individual driver that
implements
the sriov_configure PCI method.
This patch-set fixes this code duplication by moving this check from
drivers to the sriov_nuvfs_store() routine just before invoking
sriov_configure() when num_vfs is equal to 0.
Vasundhara Volam (4):
pci: move pci_assivned_vfs() check while disabling VFs to pci
sub-system
bnx2x: remove pci_assigned_vfs() check while disabling VFs
i40e: remove pci_assigned_vfs() check while disabling VFs
qlcnic: remove pci_assigned_vfs() check while disabling VFs
drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c | 2 +-
drivers/net/ethernet/intel/i40e/i40e_virtchnl_pf.c | 7 +------
.../net/ethernet/qlogic/qlcnic/qlcnic_sriov_pf.c | 10 ----------
drivers/pci/pci-sysfs.c | 5 +++++
4 files changed, 7 insertions(+), 17 deletions(-)
I have had a side conversation with Alex Williamson, VFIO author.
VFIO is the upstream method that device-assignment is managed/handled
on kvm now.
It does not set the PCI_DEV_FLAGS_ASSIGNED pci dev-flags, and thus,
this check will not work when VFIO is used.
This patch set will only work for the former, kvm-managed, device-
assignment method,
which is currently being deprecated in qemu as well.
So, yes, it works for kvm managed device-assignment, but not the
newer, VFIO-based device-assignment.
Note, also, that the pci_assigned_vfs() check in the drivers will
always return 0 when VFIO is used for device assignment, so keeping
these checks in the drivers doesn't do what they imply either.
So, taking in the patch solves old, kvm-managed, device assignment,
but a new method is needed when VFIO is involved.
- Don
ps -- Note: just adding the flag setting in vfio-pci does not necessarily
solve this problem. VFIO does not know if a device is assigned to a
guest;
it only knows a caller of the ioctl requesting the device to be assigned
to vfio, and to be dma-mapped for a region of memory, has been
requested.
So, a new PF<->VF mechanism needs to be put in place to
determine the equivalent information.
pps -- Note: testing pci_assivned_vfs() is racy, nothing prevents the flag
being added to a device between your check and removing the VF
device.
This is one of the reasons that vfio-pci doesn't use it and that this
interface should be discouraged in the kernel.
Alex/Don, I agree with the points you've raised.
But, I'd like to know whether you think this patch-set should be accepted or not.
Even though this patch-set doesn't fix any of the pending issues raised here,
it's a small step forward as it reduces the number of invocations of pci_assigned_vfs()
check which is a good thing.
thanks,
-Sathya
IMO, it's only a fix for XEN. Upstream has moved on to VFIO-based device assignment,
and these patches do not fix the issue. They don't make it any worse, either,
but I don't want someone scanning the patch list thinking it's been fixed either.
So, it's ok (but racy, as it is today) for kvm-managed device-assignment & Xen
pci passthrough, but does zip for VFIO-based assignment.
We need a new api - maybe another/new state in sysfs, so userspace can set it
(like qemu &/or libvirt), as well as (xen) kernel ... and meeting non-racy condition(s).
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