From: Keqian Zhu <zhukeqian1@huawei.com>
To: Lu Baolu <baolu.lu@linux.intel.com>,
<linux-kernel@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<iommu@lists.linux-foundation.org>,
Robin Murphy <robin.murphy@arm.com>,
Will Deacon <will@kernel.org>, "Joerg Roedel" <joro@8bytes.org>,
Yi Sun <yi.y.sun@linux.intel.com>,
"Jean-Philippe Brucker" <jean-philippe@linaro.org>,
Jonathan Cameron <Jonathan.Cameron@huawei.com>,
Tian Kevin <kevin.tian@intel.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
Kirti Wankhede <kwankhede@nvidia.com>,
<wanghaibin.wang@huawei.com>, <jiangkunkun@huawei.com>,
<yuzenghui@huawei.com>, <lushenming@huawei.com>
Subject: Re: [PATCH v3 02/12] iommu: Add iommu_split_block interface
Date: Tue, 20 Apr 2021 15:32:25 +0800 [thread overview]
Message-ID: <a09830f8-b08f-9b80-8f75-17f13088ff6d@huawei.com> (raw)
In-Reply-To: <3c34baf1-6a57-5666-38a2-0c9d6188b8b8@linux.intel.com>
Hi Baolu,
Cheers for the your quick reply.
On 2021/4/20 10:09, Lu Baolu wrote:
> Hi Keqian,
>
> On 4/20/21 9:25 AM, Keqian Zhu wrote:
>> Hi Baolu,
>>
>> On 2021/4/19 21:33, Lu Baolu wrote:
>>> Hi Keqian,
>>>
>>> On 2021/4/19 17:32, Keqian Zhu wrote:
>>>>>> +EXPORT_SYMBOL_GPL(iommu_split_block);
>>>>> Do you really have any consumers of this interface other than the dirty
>>>>> bit tracking? If not, I don't suggest to make this as a generic IOMMU
>>>>> interface.
>>>>>
>>>>> There is an implicit requirement for such interfaces. The
>>>>> iommu_map/unmap(iova, size) shouldn't be called at the same time.
>>>>> Currently there's no such sanity check in the iommu core. A poorly
>>>>> written driver could mess up the kernel by misusing this interface.
>>>> Yes, I don't think up a scenario except dirty tracking.
>>>>
>>>> Indeed, we'd better not make them as a generic interface.
>>>>
>>>> Do you have any suggestion that underlying iommu drivers can share these code but
>>>> not make it as a generic iommu interface?
>>>>
>>>> I have a not so good idea. Make the "split" interfaces as a static function, and
>>>> transfer the function pointer to start_dirty_log. But it looks weird and inflexible.
>>>
>>> I understand splitting/merging super pages is an optimization, but not a
>>> functional requirement. So is it possible to let the vendor iommu driver
>>> decide whether splitting super pages when starting dirty bit tracking
>>> and the opposite operation during when stopping it? The requirement for
>> Right. If I understand you correct, actually that is what this series does.
>
> I mean to say no generic APIs, jut do it by the iommu subsystem itself.
> It's totally transparent to the upper level, just like what map() does.
> The upper layer doesn't care about either super page or small page is
> in use when do a mapping, right?
>
> If you want to consolidate some code, how about putting them in
> start/stop_tracking()?
Yep, this reminds me. What we want to reuse is the logic of "chunk by chunk" in split().
We can implement switch_dirty_log to be "chunk by chunk" too (just the same as sync/clear),
then the vendor iommu driver can invoke it's own private implementation of split().
So we can completely remove split() in the IOMMU core layer.
example code logic
iommu.c:
switch_dirty_log(big range) {
for_each_iommu_page(big range) {
ops->switch_dirty_log(iommu_pgsize)
}
}
vendor iommu driver:
switch_dirty_log(iommu_pgsize) {
if (enable) {
ops->split_block(iommu_pgsize)
/* And other actions, such as enable hardware capability */
} else {
for_each_continuous_physical_address(iommu_pgsize)
ops->merge_page()
}
}
Besides, vendor iommu driver can invoke split() in clear_dirty_log instead of in switch_dirty_log.
The benefit is that we usually clear dirty log gradually during dirty tracking, then we can split
large page mapping gradually, which speedup start_dirty_log and make less side effect on DMA performance.
Does it looks good for you?
Thanks,
Keqian
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-04-20 7:34 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-13 8:54 [PATCH v3 00/12] iommu/smmuv3: Implement hardware dirty log tracking Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 01/12] iommu: Introduce dirty log tracking framework Keqian Zhu
2021-04-14 7:00 ` Lu Baolu
2021-04-15 6:18 ` Keqian Zhu
2021-04-15 7:03 ` Lu Baolu
2021-04-15 7:43 ` Keqian Zhu
2021-04-15 10:21 ` Lu Baolu
2021-04-16 9:07 ` Keqian Zhu
2021-04-19 1:59 ` Lu Baolu
2021-04-13 8:54 ` [PATCH v3 02/12] iommu: Add iommu_split_block interface Keqian Zhu
2021-04-14 7:14 ` Lu Baolu
2021-04-19 9:32 ` Keqian Zhu
2021-04-19 13:33 ` Lu Baolu
2021-04-20 1:25 ` Keqian Zhu
2021-04-20 2:09 ` Lu Baolu
2021-04-20 7:32 ` Keqian Zhu [this message]
2021-04-20 7:53 ` Lu Baolu
2021-04-13 8:54 ` [PATCH v3 03/12] iommu: Add iommu_merge_page interface Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 04/12] iommu/arm-smmu-v3: Add support for Hardware Translation Table Update Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 05/12] iommu/arm-smmu-v3: Enable HTTU for stage1 with io-pgtable mapping Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 06/12] iommu/arm-smmu-v3: Add feature detection for BBML Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 07/12] iommu/arm-smmu-v3: Realize split_block iommu ops Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 08/12] iommu/arm-smmu-v3: Realize merge_page " Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 09/12] iommu/arm-smmu-v3: Realize switch_dirty_log " Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 10/12] iommu/arm-smmu-v3: Realize sync_dirty_log " Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 11/12] iommu/arm-smmu-v3: Realize clear_dirty_log " Keqian Zhu
2021-04-13 8:54 ` [PATCH v3 12/12] iommu/arm-smmu-v3: Add HWDBM device feature reporting Keqian Zhu
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=a09830f8-b08f-9b80-8f75-17f13088ff6d@huawei.com \
--to=zhukeqian1@huawei.com \
--cc=Jonathan.Cameron@huawei.com \
--cc=alex.williamson@redhat.com \
--cc=baolu.lu@linux.intel.com \
--cc=cohuck@redhat.com \
--cc=iommu@lists.linux-foundation.org \
--cc=jean-philippe@linaro.org \
--cc=jiangkunkun@huawei.com \
--cc=joro@8bytes.org \
--cc=kevin.tian@intel.com \
--cc=kwankhede@nvidia.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lushenming@huawei.com \
--cc=robin.murphy@arm.com \
--cc=wanghaibin.wang@huawei.com \
--cc=will@kernel.org \
--cc=yi.y.sun@linux.intel.com \
--cc=yuzenghui@huawei.com \
/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).