Re: [PATCH v6 0/8] mmu notifier provide context informations

[Andrew Morton <akpm@linux-foundation.org>]

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?