IOMMU DMA-mapping API for arm64 ?

IOMMU DMA-mapping API for arm64 ?

[Ritesh Harjani]

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Hi everyone,

I tried looking for IOMMU support in ARM64 but what I was able to see is
only swiotlb is currently supported.

Based on my understanding for IOMMU support, we need DMA-MAPPING API to
have IOMMU ops field, similar to what is present in arm32.
I could see the iommu field added in dev_archdata in below mentioned patch
(arch/arm64/include/asm/device.h), but there is no ops field in
arch/arm64/mm/dma-mapping.c ?

I also saw one mail discussion between you guys on what is the best place
for adding iommu support in ARM64, but couldn't see any followed up patches
for the same.

Please tell us the current status/updates on the same. Your feedback will
be greatly appreciated.


commit 73150c983ac1f9b7653cfd3823b1ad4a44aad3bf
Author: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Date:   Mon Jun 10 19:34:42 2013 +0100

    arm64: device: add iommu pointer to device archdata

    When using an IOMMU for device mappings, it is necessary to keep a
    pointer between the device and the IOMMU to which it is attached in
    order to obtain the correct IOMMU when attaching the device to a domain.

    This patch adds an iommu pointer to the dev_archdata structure, in a
    similar manner to other architectures (ARM, PowerPC, x86, ...).

    Signed-off-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
    Signed-off-by: Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>


Thanks
Ritesh

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Fwd: IOMMU DMA-mapping API for arm64 ?

[Ritesh Harjani]

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"Sorry if this mail has come twice in your mailbox"

Hi everyone,

I tried looking for IOMMU support in ARM64 but what I was able to see is
only swiotlb is currently supported.

Based on my understanding for IOMMU support, we need DMA-MAPPING API to
have IOMMU ops field, similar to what is present in arm32.
I could see the iommu field added in dev_archdata in below mentioned patch
(arch/arm64/include/asm/device.h), but there is no ops field in
arch/arm64/mm/dma-mapping.c ?

I also saw one mail discussion between you guys on what is the best place
for adding iommu support in ARM64, but couldn't see any followed up patches
for the same.

Please tell us the current status/updates on the same. Your feedback will
be greatly appreciated.


commit 73150c983ac1f9b7653cfd3823b1ad4a44aad3bf
Author: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Date:   Mon Jun 10 19:34:42 2013 +0100

    arm64: device: add iommu pointer to device archdata

    When using an IOMMU for device mappings, it is necessary to keep a
    pointer between the device and the IOMMU to which it is attached in
    order to obtain the correct IOMMU when attaching the device to a domain.

    This patch adds an iommu pointer to the dev_archdata structure, in a
    similar manner to other architectures (ARM, PowerPC, x86, ...).

    Signed-off-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
    Signed-off-by: Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org>


Thanks
Ritesh

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Re: IOMMU DMA-mapping API for arm64 ?

[Will Deacon]

On Thu, Feb 06, 2014 at 05:05:45AM +0000, Ritesh Harjani wrote:
> Hi everyone,
> 
> I tried looking for IOMMU support in ARM64 but what I was able to see is
> only swiotlb is currently supported.
> 
> Based on my understanding for IOMMU support, we need DMA-MAPPING API to
> have IOMMU ops field, similar to what is present in arm32.  I could see
> the iommu field added in dev_archdata in below mentioned patch
> (arch/arm64/include/asm/device.h), but there is no ops field in
> arch/arm64/mm/dma-mapping.c ?

Correct, there needs to be a way to plumb dma-mapping into the IOMMU layer.

> I also saw one mail discussion between you guys on what is the best place
> for adding iommu support in ARM64, but couldn't see any followed up
> patches for the same.
> 
> Please tell us the current status/updates on the same. Your feedback will
> be greatly appreciated.

There are a few related topics here:

  (1) Moving a bunch of the boilerplate IOMMU code into a common place
      (iommu-helper.c or similar). This is because we don't want to blindly
      duplicate common code across architectures.

  (2) Standardising at least part of a system topology description in
      device-tree, so that we can deal with different combinations of
      {coherent,nocoherent} device {with,without} a series of IOMMUs.

Once both of those are sorted, the actual plumbing should be fairly
straightforward.

Will

Re: Fwd: IOMMU DMA-mapping API for arm64 ?

[Catalin Marinas]

On Thu, Feb 06, 2014 at 05:21:53AM +0000, Ritesh Harjani wrote:
> I also saw one mail discussion between you guys on what is the best place for
> adding iommu support in ARM64, but couldn't see any followed up patches for the
> same.

The decision was to make take the iommu code from arch/arm and turn it
into a library similar to swiotlb which can be used by the arch code. It
is on our to-do list but no ETA yet. If you volunteer to help it would
be great ;)

-- 
Catalin

Re: Fwd: IOMMU DMA-mapping API for arm64 ?

[Ritesh Harjani]

On Thu, Feb 6, 2014 at 3:43 PM, Catalin Marinas <catalin.marinas-5wv7dgnIgG8@public.gmane.org> wrote:
> On Thu, Feb 06, 2014 at 05:21:53AM +0000, Ritesh Harjani wrote:
>> I also saw one mail discussion between you guys on what is the best place for
>> adding iommu support in ARM64, but couldn't see any followed up patches for the
>> same.
>
> The decision was to make take the iommu code from arch/arm and turn it
> into a library similar to swiotlb which can be used by the arch code. It
> is on our to-do list but no ETA yet. If you volunteer to help it would
> be great ;)

Sure Catalin, will take out the common code from arch/arm and put into
lib/iommu-helper which is the best place as discussed in many mail
chains.
Let me see how far I can go. Will keep you posted.

>
> --
> Catalin

Thanks
Ritesh