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()?
Best regards,
baolu
We realized split/merge in IOMMU core layer, but don't force vendor driver to
use it.
The problem is that when we expose these interfaces to vendor IOMMU driver,
will also
expose them to upper driver.
upper layer is that starting/stopping dirty bit tracking and
mapping/unmapping are mutually exclusive.
OK, I will explicitly add the hints. Thanks.
Thanks,
Keqian
On the other hand, if a driver calls map/unmap with split/merge at the same
time,
it's a bug of driver, it should follow the rule.
Best regards,
baolu
.