On 2/7/2023 8:56 AM, Gupta, Nipun wrote:
[AMD Official Use Only - General]
Hi David,
I agree that change is not straightforward to review, but it should not cause
any functional issue as we are still creating all the memory mappings, but one
by one for each segment.
For hot plug case this causes issue as mentioned, that VFIO does not allow
unmap of the individual segments in case mapping was created of a single
coalesced segment.
But yes, I am not sure why this code was added, which Anatoly may have more
understanding on.
The motivation behind this code was that Linux allows limited amount of
page mappings, so we were trying to save on those. However, since then
there have been a few changes related to partial unmaps that may make it
so that this code is not only no longer necessary, but is in fact
actively harmful. I agree that this at least warrants a second look.
Anatoly,
Can you please provide your feedback on this change?
The patch probably shouldn't include the mailmap changes :)
Could you please provide some steps to reproduce the hotplug issue
you're having? It would be great to have a test case for this patchset
to put it in context.
--
Thanks,
Anatoly
