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From: Lu Baolu <>
To: Daniel Drake <>
	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 10:48:55 +0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hi Daniel,

On 2020/4/13 10:25, Daniel Drake wrote:
> 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)

Both are trying to solve a same problem.

I have sync'ed with Joerg. This patch set will be replaced with Joerg's
proposal due to a race concern between domain switching and driver
binding. I will rebase all vt-d patches in this set on top of Joerg's

Best regards,

> 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

  reply	other threads:[~2020-04-13  2:49 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
2020-04-13  2:48       ` Lu Baolu [this message]
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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