linux-kernel - Re: [PATCH v5 00/13] Copy Offload in NVMe Fabrics with P2P PCI Memory

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Date:   Thu, 30 Aug 2018 15:20:12 -0400
From:   Jerome Glisse <jglisse@...hat.com>
To:     Logan Gunthorpe <logang@...tatee.com>
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-block@...r.kernel.org,
        Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Keith Busch <keith.busch@...el.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Christian König <christian.koenig@....com>
Subject: Re: [PATCH v5 00/13] Copy Offload in NVMe Fabrics with P2P PCI Memory

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.

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.

Maybe i have miss it in some of the patch. I just skimmed over for
now.

Cheers,
Jérôme