linux-pci.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Bjorn Helgaas <helgaas@kernel.org>
To: Eric Pilmore <epilmore@gigaio.com>
Cc: linux-pci@vger.kernel.org, David Woodhouse <dwmw2@infradead.org>,
	Logan Gunthorpe <logang@deltatee.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	iommu@lists.linux-foundation.org
Subject: Re: IOAT DMA w/IOMMU
Date: Thu, 9 Aug 2018 13:43:31 -0500	[thread overview]
Message-ID: <20180809184331.GB113140@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <CAOQPn8soxubJxb=vp7kz+AM6LbPH5y+_Nx0Vzv7rjV_nMMqEmA@mail.gmail.com>

[+cc David, Logan, Alex, iommu list]

On Thu, Aug 09, 2018 at 11:14:13AM -0700, Eric Pilmore wrote:
> Didn't get any response on the IRC channel so trying here.
> 
> Was wondering if anybody here has used IOAT DMA engines with an
> IOMMU turned on (Xeon based system)? My specific question is really
> whether it is possible to DMA (w/IOAT) to a PCI BAR address as the
> destination without having to map that address to the IOVA space of
> the DMA engine first (assuming the IOMMU is on)?

So is this a peer-to-peer DMA scenario?  You mention DMA, which would
be a transaction initiated by a PCI device, to a PCI BAR address, so
it doesn't sound like system memory is involved.

I copied some folks who know a lot more about this than I do.

> I am encountering issues where I see PTE Errors reported from DMAR
> in this scenario, but I do not if I use a different DMA engine
> that's sitting downstream off the PCI tree. I'm wondering if the
> IOAT DMA failure is some artifact of these engines sitting behind
> the Host Bridge.
> 
> Thanks in advance!
> Eric

  reply	other threads:[~2018-08-09 21:09 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-09 18:14 IOAT DMA w/IOMMU Eric Pilmore
2018-08-09 18:43 ` Bjorn Helgaas [this message]
2018-08-09 18:51   ` Eric Pilmore
2018-08-09 19:35     ` Logan Gunthorpe
2018-08-09 19:47       ` Kit Chow
2018-08-09 20:11         ` Logan Gunthorpe
2018-08-09 20:57           ` Kit Chow
2018-08-09 21:11             ` Logan Gunthorpe
2018-08-09 21:47               ` Kit Chow
2018-08-09 22:40                 ` Jiang, Dave
2018-08-09 22:48                   ` Kit Chow
2018-08-09 22:50                     ` Logan Gunthorpe
2018-08-09 23:00                       ` Kit Chow
2018-08-10 16:02                         ` Kit Chow
2018-08-10 16:23                           ` Kit Chow
2018-08-10 16:24                             ` Logan Gunthorpe
2018-08-10 16:24                           ` Logan Gunthorpe
2018-08-10 16:31                             ` Dave Jiang
2018-08-10 16:33                               ` Logan Gunthorpe
2018-08-10 17:01                                 ` Dave Jiang
2018-08-10 17:15                                   ` Logan Gunthorpe
2018-08-10 17:46                                     ` Dave Jiang
2018-08-11  0:53                                       ` Kit Chow
2018-08-11  2:10                                         ` Logan Gunthorpe
2018-08-13 14:23                                           ` Kit Chow
2018-08-13 14:59                                             ` Robin Murphy
2018-08-13 15:21                                               ` Kit Chow
2018-08-13 23:30                                                 ` Kit Chow
2018-08-13 23:39                                                   ` Logan Gunthorpe
2018-08-13 23:48                                                     ` Kit Chow
2018-08-13 23:50                                                       ` Logan Gunthorpe
2018-08-14 13:47                                                         ` Kit Chow
2018-08-14 14:03                                                         ` Robin Murphy
2018-08-13 23:36                                                 ` Kit Chow
2018-08-09 21:31       ` Eric Pilmore
2018-08-09 21:36         ` Logan Gunthorpe
2018-08-16 17:16           ` Kit Chow
2018-08-16 17:21             ` Logan Gunthorpe
2018-08-16 18:53               ` Kit Chow
2018-08-16 18:56                 ` Logan Gunthorpe
2018-08-21 23:18                   ` Eric Pilmore
2018-08-21 23:20                     ` Logan Gunthorpe
2018-08-21 23:28                       ` Eric Pilmore
2018-08-21 23:35                         ` Logan Gunthorpe
2018-08-21 23:45                           ` Eric Pilmore
2018-08-21 23:53                             ` Logan Gunthorpe
2018-08-21 23:59                               ` Eric Pilmore
2018-08-21 23:30                       ` Eric Pilmore

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180809184331.GB113140@bhelgaas-glaptop.roam.corp.google.com \
    --to=helgaas@kernel.org \
    --cc=alex.williamson@redhat.com \
    --cc=dwmw2@infradead.org \
    --cc=epilmore@gigaio.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=linux-pci@vger.kernel.org \
    --cc=logang@deltatee.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).