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From: Daniel Drake <>
To: Lu Baolu <>
Cc: Jon Derrick <>,
	Joerg Roedel <>,,
	Bjorn Helgaas <>,
	Linux PCI <>,
	Linux Upstreaming Team <>
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: <> (raw)
In-Reply-To: <>

On Fri, Apr 10, 2020 at 9:22 AM Lu Baolu <> 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.
> 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
(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.

> 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

I didn't try Joerg's iommu group rework yet as it conflicts with those
patches above.


  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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