From: Eric Pilmore <epilmore@gigaio.com>
To: Bjorn Helgaas <helgaas@kernel.org>
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 11:51:53 -0700 [thread overview]
Message-ID: <CAOQPn8uPYKai49WYPqZp2wNd5of=0hUvPOHEtqP56RZu-hcjuw@mail.gmail.com> (raw)
In-Reply-To: <20180809184331.GB113140@bhelgaas-glaptop.roam.corp.google.com>
On Thu, Aug 9, 2018 at 11:43 AM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> [+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.
No, not peer-to-peer. This is from system memory (e.g. SKB buffer which
has had an IOMMU mapping created) to a PCI BAR address.
>
> I copied some folks who know a lot more about this than I do.
Thank you!
>
>> 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
next prev parent reply other threads:[~2018-08-09 18:51 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
2018-08-09 18:51 ` Eric Pilmore [this message]
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
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