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From: Alex Williamson <alex.williamson@redhat.com>
To: Logan Gunthorpe <logang@deltatee.com>
Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-doc@vger.kernel.org, "Stephen Bates" <sbates@raithlin.com>,
	"Christoph Hellwig" <hch@lst.de>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	"Marc Zyngier" <marc.zyngier@arm.com>,
	"Kai-Heng Feng" <kai.heng.feng@canonical.com>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Christian König" <christian.koenig@amd.com>,
	"Matthew Wilcox" <willy@infradead.org>
Subject: Re: [PATCH v7 4/4] PCI: Introduce the disable_acs_redir parameter
Date: Tue, 17 Jul 2018 11:48:48 -0600
Message-ID: <20180717114848.2914d547@t450s.home> (raw)
In-Reply-To: <20180717170204.30470-5-logang@deltatee.com>

On Tue, 17 Jul 2018 11:02:04 -0600
Logan Gunthorpe <logang@deltatee.com> wrote:

> In order to support P2P traffic on a segment of the PCI hierarchy,
> we must be able to disable the ACS redirect bits for select
> PCI bridges. The bridges must be selected before the devices are
> discovered by the kernel and the IOMMU groups created. Therefore,
> a kernel command line parameter is created to specify devices
> which must have their ACS bits disabled.
> 
> The new parameter takes a list of devices separated by a semicolon.
> Each device specified will have it's ACS redirect bits disabled.
> This is similar to the existing 'resource_alignment' parameter.
> 
> The ACS Request P2P Request Redirect, P2P Completion Redirect and P2P
> Egress Control bits are disabled which is sufficient to always allow
> passing P2P traffic uninterrupted. The bits are set after the kernel
> (optionally) enables the ACS bits itself. It is also done regardless of
> whether the kernel sets the bits or not seeing some BIOS firmware is known
> to set the bits on boot.
> 
> If the user tries to disable the ACS redirct for a device without the
> ACS capability, a warning is printed to dmesg.
> 
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Reviewed-by: Stephen Bates <sbates@raithlin.com>
> Acked-by: Christian König <christian.koenig@amd.com>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  9 +++
>  drivers/pci/pci.c                               | 76 ++++++++++++++++++++++++-
>  2 files changed, 83 insertions(+), 2 deletions(-)

Thanks for the re-spins!

Reviewed-by: Alex Williamson <alex.williamson@redhat.com>

  reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-17 17:02 [PATCH v7 0/4] Add parameter for disabling ACS redirection for P2P Logan Gunthorpe
2018-07-17 17:02 ` [PATCH v7 1/4] PCI: Make specifying PCI devices in kernel parameters reusable Logan Gunthorpe
2018-07-17 17:02 ` [PATCH v7 2/4] PCI: Allow specifying devices using a base bus and path of devfns Logan Gunthorpe
2018-07-17 17:02 ` [PATCH v7 3/4] PCI: Introduce disable_acs_redir quirk Logan Gunthorpe
2018-07-17 17:48   ` Alex Williamson
2018-07-17 17:02 ` [PATCH v7 4/4] PCI: Introduce the disable_acs_redir parameter Logan Gunthorpe
2018-07-17 17:48   ` Alex Williamson [this message]
2018-07-17 17:49     ` Logan Gunthorpe
2018-07-17 17:57       ` Stephen  Bates
2018-07-17 20:39 ` lspci: Display path to device Matthew Wilcox
2018-07-17 20:51   ` Logan Gunthorpe
2018-07-17 21:00   ` Bjorn Helgaas
2018-07-17 21:46     ` Matthew Wilcox
2018-08-09 23:48   ` Matthew Wilcox
2018-08-10  9:35   ` Martin Mares
2018-08-10 10:30     ` Martin Mares
2018-08-10 14:56       ` Matthew Wilcox
2018-08-12  9:28         ` Martin Mares
2018-08-12 10:31           ` Matthew Wilcox
2018-08-12 10:51             ` Martin Mares
2018-08-13 15:55             ` Logan Gunthorpe

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