Re: Enabling RO on a VF

[Jason Gunthorpe]

On Fri, Oct 01, 2021 at 11:05:15AM +0000, Haakon Bugge wrote:
> Hey,
> 
> 
> Commit 1477d44ce47d ("RDMA/mlx5: Enable Relaxed Ordering by default
> for kernel ULPs") uses pcie_relaxed_ordering_enabled() to check if
> RO can be enabled. This function checks if the Enable Relaxed
> Ordering bit in the Device Control register is set. However, on a
> VF, this bit is RsvdP (Reserved for future RW
> implementations. Register bits are read-only and must return zero
> when read. Software must preserve the value read for writes to
> bits.).
> 
> Hence, AFAICT, RO will not be enabled when using a VF.
> 
> How can that be fixed?

When qemu takes a VF and turns it into a PF in a VM it must emulate
the RO bit and return one

Jason