On 30/08/18 01:20 PM, Jerome Glisse wrote:
On Thu, Aug 30, 2018 at 12:53:39PM -0600, Logan Gunthorpe wrote:
[...]
>
> When the PCI P2PDMA config option is selected the ACS bits in every
> bridge port in the system are turned off to allow traffic to
> pass freely behind the root port. At this time, the bit must be disabled
> at boot so the IOMMU subsystem can correctly create the groups, though
> this could be addressed in the future. There is no way to dynamically
> disable the bit and alter the groups.
Oh, sorry this paragraph in the cover letter is wrong now. We now rely
on the disable_acs_redir command line option introduced in
aaca43fda742 ("PCI: Add "pci=disable_acs_redir=" parameter for
peer-to-peer support")
Can you provide an example on how to test this ? Like kernel command
line option, the doc patch does not have any such example. It would be
nice to add.
Do you mean to test the patchset or the ACS bits you quoted?
Testing the patchset is a matter of having the right hardware (ie an
RDMA NIC and CMB enabled NVMe behind a PCIe switch, with the ACS bits
set correctly by the above command line option) and setting the p2pmem
configfs attribute in an nvme-of port to 'yes'.
Logan