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SubjectRe: [PATCH v6 0/8] mmu notifier provide context informations
On Tue, 26 Mar 2019 12:47:39 -0400 jglisse@redhat.com wrote:

> From: Jérôme Glisse <jglisse@redhat.com>
>
> (Andrew this apply on top of my HMM patchset as otherwise you will have
> conflict with changes to mm/hmm.c)
>
> Changes since v5:
> - drop KVM bits waiting for KVM people to express interest if they
> do not then i will post patchset to remove change_pte_notify as
> without the changes in v5 change_pte_notify is just useless (it
> it is useless today upstream it is just wasting cpu cycles)
> - rebase on top of lastest Linus tree
>
> Previous cover letter with minor update:
>
>
> Here i am not posting users of this, they already have been posted to
> appropriate mailing list [6] and will be merge through the appropriate
> tree once this patchset is upstream.
>
> Note that this serie does not change any behavior for any existing
> code. It just pass down more information to mmu notifier listener.
>
> The rational for this patchset:
>
> CPU page table update can happens for many reasons, not only as a
> result of a syscall (munmap(), mprotect(), mremap(), madvise(), ...)
> but also as a result of kernel activities (memory compression, reclaim,
> migration, ...).
>
> This patch introduce a set of enums that can be associated with each
> of the events triggering a mmu notifier:
>
> - UNMAP: munmap() or mremap()
> - CLEAR: page table is cleared (migration, compaction, reclaim, ...)
> - PROTECTION_VMA: change in access protections for the range
> - PROTECTION_PAGE: change in access protections for page in the range
> - SOFT_DIRTY: soft dirtyness tracking
>
> Being able to identify munmap() and mremap() from other reasons why the
> page table is cleared is important to allow user of mmu notifier to
> update their own internal tracking structure accordingly (on munmap or
> mremap it is not longer needed to track range of virtual address as it
> becomes invalid). Without this serie, driver are force to assume that
> every notification is an munmap which triggers useless trashing within
> drivers that associate structure with range of virtual address. Each
> driver is force to free up its tracking structure and then restore it
> on next device page fault. With this serie we can also optimize device
> page table update [6].
>
> More over this can also be use to optimize out some page table updates
> like for KVM where we can update the secondary MMU directly from the
> callback instead of clearing it.

We seem to be rather short of review input on this patchset. ie: there
is none.

> ACKS AMD/RADEON https://lkml.org/lkml/2019/2/1/395

OK, kind of ackish, but not a review.

> ACKS RDMA https://lkml.org/lkml/2018/12/6/1473

This actually acks the infiniband part of a patch which isn't in this
series.


So we have some work to do, please. Who would be suitable reviewers?

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