From: John Garry <john.garry@huawei.com>
To: Robin Murphy <robin.murphy@arm.com>,
"joro@8bytes.org" <joro@8bytes.org>,
"will@kernel.org" <will@kernel.org>,
"jejb@linux.ibm.com" <jejb@linux.ibm.com>,
"martin.petersen@oracle.com" <martin.petersen@oracle.com>,
"hch@lst.de" <hch@lst.de>,
"m.szyprowski@samsung.com" <m.szyprowski@samsung.com>
Cc: "iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
Linuxarm <linuxarm@huawei.com>
Subject: Re: [PATCH 1/6] iommu: Move IOVA power-of-2 roundup into allocator
Date: Wed, 14 Apr 2021 18:44:58 +0100 [thread overview]
Message-ID: <8fce915b-18fa-2bfb-66d7-325cb7837894@huawei.com> (raw)
In-Reply-To: <4914d134-5a63-f683-b14b-25ab71a57cd4@huawei.com>
On 06/04/2021 17:54, John Garry wrote:
Hi Robin,
>
>> Sorry if the phrasing was unclear there - the allusion to default
>> domains is new, it just occurred to me that what we do there is in
>> fact fairly close to what I've suggested previously for this. In that
>> case, we have a global policy set by the command line, which *can* be
>> overridden per-domain via sysfs at runtime, provided the user is
>> willing to tear the whole thing down. Using a similar approach here
>> would give a fair degree of flexibility but still mean that changes
>> never have to be made dynamically to a live domain.
>
> So are you saying that we can handle it similar to how we now can handle
> changing default domain for an IOMMU group via sysfs? If so, that just
> is not practical here. Reason being that this particular DMA engine
> provides the block device giving / mount point, so if we unbind the
> driver, we lose / mount point.
>
> And I am not sure if the end user would even know how to set such a
> tunable. Or, in this case, why the end user would not want the optimized
> range configured always.
>
> I'd still rather if the device driver could provide info which can be
> used to configure this before or during probing.
As a new solution, how about do both of these:
a. Add a per-IOMMU group sysfs file to set this tunable. Works same as
how we change the default domain, and has all the same
restrictions/steps. I think that this is what you are already suggesting.
b. Provide a DMA mapping API to set this value, similar to this current
series. In the IOMMU backend for that API, we record a new range value
and return -EPROBE_DEFER when successful. In the reprobe we reset the
default domain for the devices' IOMMU group, with the IOVA domain rcache
range configured as previously requested. Again, allocating the new
default domain is similar to how we change default domain type today.
This means that we don't play with a live domain. Downside is that we
need to defer the probe.
Thanks,
John
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-04-14 17:47 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-19 13:25 [PATCH 0/6] dma mapping/iommu: Allow IOMMU IOVA rcache range to be configured John Garry
2021-03-19 13:25 ` [PATCH 1/6] iommu: Move IOVA power-of-2 roundup into allocator John Garry
2021-03-19 16:13 ` Robin Murphy
2021-03-19 16:58 ` John Garry
2021-03-19 19:20 ` Robin Murphy
2021-03-22 15:01 ` John Garry
2021-03-31 9:58 ` Robin Murphy
2021-04-06 16:54 ` John Garry
2021-04-14 17:44 ` John Garry [this message]
2021-03-19 13:25 ` [PATCH 2/6] iova: Add a per-domain count of reserved nodes John Garry
2021-03-19 13:25 ` [PATCH 3/6] iova: Allow rcache range upper limit to be configurable John Garry
2021-03-19 16:25 ` Robin Murphy
2021-03-19 17:26 ` John Garry
2021-03-31 10:53 ` Robin Murphy
2021-03-19 13:25 ` [PATCH 4/6] iommu: Add iommu_dma_set_opt_size() John Garry
2021-03-19 13:25 ` [PATCH 5/6] dma-mapping/iommu: Add dma_set_max_opt_size() John Garry
2021-03-19 17:00 ` Robin Murphy
2021-03-19 18:02 ` John Garry
2021-03-31 8:01 ` Salil Mehta
2021-03-31 8:08 ` Salil Mehta
2021-03-19 13:25 ` [PATCH 6/6] scsi: hisi_sas: Set max optimal DMA size for v3 hw John Garry
2021-03-19 13:40 ` [PATCH 0/6] dma mapping/iommu: Allow IOMMU IOVA rcache range to be configured Christoph Hellwig
2021-03-19 15:42 ` John Garry
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=8fce915b-18fa-2bfb-66d7-325cb7837894@huawei.com \
--to=john.garry@huawei.com \
--cc=hch@lst.de \
--cc=iommu@lists.linux-foundation.org \
--cc=jejb@linux.ibm.com \
--cc=joro@8bytes.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=linuxarm@huawei.com \
--cc=m.szyprowski@samsung.com \
--cc=martin.petersen@oracle.com \
--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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).