From: Daniel Drake <drake@endlessm.com>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: Jon Derrick <jonathan.derrick@intel.com>,
Joerg Roedel <joro@8bytes.org>,
iommu@lists.linux-foundation.org,
Bjorn Helgaas <helgaas@kernel.org>,
Linux PCI <linux-pci@vger.kernel.org>,
Linux Upstreaming Team <linux@endlessm.com>
Subject: Re: [PATCH 1/1] iommu/vt-d: use DMA domain for real DMA devices and subdevices
Date: Mon, 13 Apr 2020 10:25:38 +0800 [thread overview]
Message-ID: <CAD8Lp45dJ3-t6qqctiP1a=c44PEWZ-L04yv0r0=1Nrvwfouz1w@mail.gmail.com> (raw)
In-Reply-To: <09c98569-ed22-8886-3372-f5752334f8af@linux.intel.com>
On Fri, Apr 10, 2020 at 9:22 AM Lu Baolu <baolu.lu@linux.intel.com> wrote:
> This is caused by the fragile private domain implementation. We are in
> process of removing it by enhancing the iommu subsystem with per-group
> default domain.
>
> https://www.spinics.net/lists/iommu/msg42976.html
>
> So ultimately VMD subdevices should have their own per-device iommu data
> and support per-device dma ops.
Interesting. There's also this patchset you posted:
[PATCH 00/19] [PULL REQUEST] iommu/vt-d: patches for v5.7
https://lists.linuxfoundation.org/pipermail/iommu/2020-April/042967.html
(to be pushed out to 5.8)
In there you have:
> iommu/vt-d: Don't force 32bit devices to uses DMA domain
which seems to clash with the approach being explored in this thread.
And:
> iommu/vt-d: Apply per-device dma_ops
This effectively solves the trip point that caused me to open these
discussions, where intel_map_page() -> iommu_need_mapping() would
incorrectly determine that a intel-iommu DMA mapping was needed for a
PCI subdevice running in identity mode. After this patch, a PCI
subdevice in identity mode uses the default system dma_ops and
completely avoids intel-iommu.
So that solves the issues I was looking at. Jon, you might want to
check if the problems you see are likewise solved for you by these
patches.
I didn't try Joerg's iommu group rework yet as it conflicts with those
patches above.
Daniel
next prev parent reply other threads:[~2020-04-13 2:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-09 19:17 [PATCH 0/1] Real DMA dev DMA domain patch Jon Derrick
2020-04-09 19:17 ` [PATCH 1/1] iommu/vt-d: use DMA domain for real DMA devices and subdevices Jon Derrick
2020-04-10 1:22 ` Lu Baolu
2020-04-13 2:25 ` Daniel Drake [this message]
2020-04-13 2:48 ` Lu Baolu
2020-04-13 16:08 ` Derrick, Jonathan
2020-04-18 12:13 ` Joerg Roedel
2020-04-12 3:50 ` Daniel Drake
2020-04-12 7:35 ` Christoph Hellwig
2020-04-13 16:08 ` Derrick, Jonathan
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