From: isaacm@codeaurora.org
To: Will Deacon <will@kernel.org>
Cc: kernel-team@android.com, Robin Murphy <robin.murphy@arm.com>,
linux-kernel@vger.kernel.org, Liam Mark <lmark@codeaurora.org>,
iommu@lists.linux-foundation.org, pratikp@codeaurora.org
Subject: Re: [RFC PATCH] iommu/dma: Allow drivers to reserve an iova range
Date: Wed, 19 Feb 2020 12:06:28 -0800 [thread overview]
Message-ID: <d8b70a579f07c688b264e83a0ec0b6d6@codeaurora.org> (raw)
In-Reply-To: <20200219111501.GA19400@willie-the-truck>
On 2020-02-19 03:15, Will Deacon wrote:
> On Tue, Feb 18, 2020 at 05:57:18PM -0800, isaacm@codeaurora.org wrote:
>> On 2020-02-17 07:50, Robin Murphy wrote:
>> > On 17/02/2020 8:01 am, Christoph Hellwig wrote:
>> > > On Fri, Feb 14, 2020 at 02:58:16PM -0800, Isaac J. Manjarres wrote:
>> > > > From: Liam Mark <lmark@codeaurora.org>
>> > > >
>> > > > Some devices have a memory map which contains gaps or holes.
>> > > > In order for the device to have as much IOVA space as possible,
>> > > > allow its driver to inform the DMA-IOMMU layer that it should
>> > > > not allocate addresses from these holes.
>> > >
>> > > Layering violation. dma-iommu is the translation layer between the
>> > > DMA API and the IOMMU API. And calls into it from drivers performing
>> > > DMA mappings need to go through the DMA API (and be documented there).
>> >
>> > +1
>> >
>> > More than that, though, we already have "holes in the address space"
>> > support for the sake of PCI host bridge windows - assuming this is the
>> > same kind of thing (i.e. the holes are between memory regions and
>> > other resources in PA space, so are only relevant once address
>> > translation comes into the picture), then this is IOMMU API level
>> To make sure that we're on the same page, this support alludes to the
>> handling in
>> dma-iommu.c that reserves portions of the IOVA space for the PCI host
>> bridge
>> windows,
>> correct? If so, then yes, this is similar.
>> > stuff, so even a DMA API level interface would be inappropriate.
>> Does this mean that the driver should be managing the IOVA space and
>> mappings for this device using the IOMMU API? If so, is the rationale
>> for
>> this because the device driver can have the information of what IOVA
>> ranges
>> can and cannot be used? Shouldn't there be a generic way of informing
>> an
>> IOMMU driver about these reserved ranges? Perhaps through a device
>> tree
>> property, instead of deferring this type of management to the driver?
>
> Before we dive into designing that, can you please clarify whether the
> reserved IOVA range applies to all DMA masters mastering through a
> particular SMMU, or whether it's just about one specific master? I was
> assuming the former, but wanted to be sure.
>
This situation currently applies to one master.
> Thanks,
>
> Will
Thanks,
Isaac
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
WARNING: multiple messages have this Message-ID (diff)
From: isaacm@codeaurora.org
To: Will Deacon <will@kernel.org>
Cc: Robin Murphy <robin.murphy@arm.com>,
Christoph Hellwig <hch@infradead.org>,
pratikp@codeaurora.org, linux-kernel@vger.kernel.org,
Liam Mark <lmark@codeaurora.org>,
iommu@lists.linux-foundation.org, kernel-team@android.com
Subject: Re: [RFC PATCH] iommu/dma: Allow drivers to reserve an iova range
Date: Wed, 19 Feb 2020 12:06:28 -0800 [thread overview]
Message-ID: <d8b70a579f07c688b264e83a0ec0b6d6@codeaurora.org> (raw)
In-Reply-To: <20200219111501.GA19400@willie-the-truck>
On 2020-02-19 03:15, Will Deacon wrote:
> On Tue, Feb 18, 2020 at 05:57:18PM -0800, isaacm@codeaurora.org wrote:
>> On 2020-02-17 07:50, Robin Murphy wrote:
>> > On 17/02/2020 8:01 am, Christoph Hellwig wrote:
>> > > On Fri, Feb 14, 2020 at 02:58:16PM -0800, Isaac J. Manjarres wrote:
>> > > > From: Liam Mark <lmark@codeaurora.org>
>> > > >
>> > > > Some devices have a memory map which contains gaps or holes.
>> > > > In order for the device to have as much IOVA space as possible,
>> > > > allow its driver to inform the DMA-IOMMU layer that it should
>> > > > not allocate addresses from these holes.
>> > >
>> > > Layering violation. dma-iommu is the translation layer between the
>> > > DMA API and the IOMMU API. And calls into it from drivers performing
>> > > DMA mappings need to go through the DMA API (and be documented there).
>> >
>> > +1
>> >
>> > More than that, though, we already have "holes in the address space"
>> > support for the sake of PCI host bridge windows - assuming this is the
>> > same kind of thing (i.e. the holes are between memory regions and
>> > other resources in PA space, so are only relevant once address
>> > translation comes into the picture), then this is IOMMU API level
>> To make sure that we're on the same page, this support alludes to the
>> handling in
>> dma-iommu.c that reserves portions of the IOVA space for the PCI host
>> bridge
>> windows,
>> correct? If so, then yes, this is similar.
>> > stuff, so even a DMA API level interface would be inappropriate.
>> Does this mean that the driver should be managing the IOVA space and
>> mappings for this device using the IOMMU API? If so, is the rationale
>> for
>> this because the device driver can have the information of what IOVA
>> ranges
>> can and cannot be used? Shouldn't there be a generic way of informing
>> an
>> IOMMU driver about these reserved ranges? Perhaps through a device
>> tree
>> property, instead of deferring this type of management to the driver?
>
> Before we dive into designing that, can you please clarify whether the
> reserved IOVA range applies to all DMA masters mastering through a
> particular SMMU, or whether it's just about one specific master? I was
> assuming the former, but wanted to be sure.
>
This situation currently applies to one master.
> Thanks,
>
> Will
Thanks,
Isaac
next prev parent reply other threads:[~2020-02-19 20:06 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 22:58 [RFC PATCH] iommu/dma: Allow drivers to reserve an iova range Isaac J. Manjarres
2020-02-14 22:58 ` Isaac J. Manjarres
2020-02-17 8:01 ` Christoph Hellwig
2020-02-17 8:01 ` Christoph Hellwig
2020-02-17 15:50 ` Robin Murphy
2020-02-17 15:50 ` Robin Murphy
2020-02-19 1:57 ` isaacm
2020-02-19 1:57 ` isaacm
2020-02-19 11:15 ` Will Deacon
2020-02-19 11:15 ` Will Deacon
2020-02-19 20:06 ` isaacm [this message]
2020-02-19 20:06 ` isaacm
2020-02-20 8:45 ` Will Deacon
2020-02-20 8:45 ` Will Deacon
2020-02-20 18:57 ` Pratik Patel
2020-02-20 18:57 ` Pratik Patel
2020-02-19 9:46 ` Joerg Roedel
2020-02-19 9:46 ` Joerg Roedel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d8b70a579f07c688b264e83a0ec0b6d6@codeaurora.org \
--to=isaacm@codeaurora.org \
--cc=iommu@lists.linux-foundation.org \
--cc=kernel-team@android.com \
--cc=linux-kernel@vger.kernel.org \
--cc=lmark@codeaurora.org \
--cc=pratikp@codeaurora.org \
--cc=robin.murphy@arm.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.