linux-kernel - Re: [PATCH 0/3] Add parameter for disabling ACS redirection for P2P

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Message-ID: <2aec7435-e59b-9ef8-825f-029188f6e549@amd.com>
Date:   Fri, 25 May 2018 10:28:31 +0200
From:   Christian König <christian.koenig@....com>
To:     Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-doc@...r.kernel.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Christoffer Dall <cdall@...aro.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Alex Williamson <alex.williamson@...hat.com>
Subject: Re: [PATCH 0/3] Add parameter for disabling ACS redirection for P2P

Am 24.05.2018 um 23:48 schrieb Logan Gunthorpe:
> Hi,
>
> As discussed in our PCI P2PDMA series, we'd like to add a kernel
> parameter for selectively disabling ACS redirection for select
> bridges. Seeing this turned out to be a small series in itself, we've
> decided to send this separately from the P2P work.
>
> This series generalizes the code already done for the resource_alignment
> option that already exists. The first patch creates a helper function
> to match PCI devices against strings based on the code that already
> existed in pci_specified_resource_alignment().
>
> The second patch expands the new helper to optionally take a path of
> PCI devfns. This is to address Alex's renumbering concern when using
> simple bus-devfns. The implementation is essentially how he described it and
> similar to the Intel VT-d spec (Section 8.3.1).
>
> The final patch adds the disable_acs_redir kernel parameter which takes
> a list of PCI devices and will disable the ACS P2P Request Redirect,
> ACS P2P Completion Redirect and ACS P2P Egress Control bits for the
> selected devices. This allows P2P traffic between selected bridges and
> seeing it's done at boot, before IOMMU group creating the IOMMU groups
> will be created correctly based on the bits.
>
> Thanks,
>
> Logan
>
>
> Logan Gunthorpe (3):
>    PCI: Make specifying PCI devices in kernel parameters reusable
>    PCI: Allow specifying devices using a base bus and path of devfns
>    PCI: Introduce the disable_acs_redir parameter

Thanks a lot of taking care of it like that. It looks much cleaner to me 
than just trying to disable ACS without a parameter.

Series is Acked-by: Christian König <christian.koenig@....com>.

Thanks,
Christian.


>
>   Documentation/admin-guide/kernel-parameters.txt |  39 ++-
>   drivers/pci/pci.c                               | 358 ++++++++++++++++++++----
>   2 files changed, 336 insertions(+), 61 deletions(-)
>
> --
> 2.11.0