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Diffstat (limited to 'cover-letter')
| -rw-r--r-- | cover-letter | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/cover-letter b/cover-letter new file mode 100644 index 000000000000..37b8d9ed7af4 --- /dev/null +++ b/cover-letter @@ -0,0 +1,88 @@ +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) + +Updated cover letter: + + +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. + +ACKS AMD/RADEON https://lkml.org/lkml/2019/2/1/395 +ACKS RDMA https://lkml.org/lkml/2018/12/6/1473 + +Cheers, +Jérôme + +[1] v1 https://lkml.org/lkml/2018/3/23/1049 +[2] v2 https://lkml.org/lkml/2018/12/5/10 +[3] v3 https://lkml.org/lkml/2018/12/13/620 +[4] v4 https://lkml.org/lkml/2019/1/23/838 +[5] v5 https://lkml.org/lkml/2019/2/19/752 +[6] patches to use this: + https://lkml.org/lkml/2019/1/23/833 + https://lkml.org/lkml/2019/1/23/834 + https://lkml.org/lkml/2019/1/23/832 + https://lkml.org/lkml/2019/1/23/831 + +Cc: Andrew Morton <akpm@linux-foundation.org> +Cc: linux-mm@kvack.org +Cc: Christian König <christian.koenig@amd.com> +Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> +Cc: Jani Nikula <jani.nikula@linux.intel.com> +Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> +Cc: Jan Kara <jack@suse.cz> +Cc: Andrea Arcangeli <aarcange@redhat.com> +Cc: Peter Xu <peterx@redhat.com> +Cc: Felix Kuehling <Felix.Kuehling@amd.com> +Cc: Jason Gunthorpe <jgg@mellanox.com> +Cc: Ross Zwisler <zwisler@kernel.org> +Cc: Dan Williams <dan.j.williams@intel.com> +Cc: Paolo Bonzini <pbonzini@redhat.com> +Cc: Alex Deucher <alexander.deucher@amd.com> +Cc: Radim Krčmář <rkrcmar@redhat.com> +Cc: Michal Hocko <mhocko@kernel.org> +Cc: Christian Koenig <christian.koenig@amd.com> +Cc: Ralph Campbell <rcampbell@nvidia.com> +Cc: John Hubbard <jhubbard@nvidia.com> +Cc: kvm@vger.kernel.org +Cc: dri-devel@lists.freedesktop.org +Cc: linux-rdma@vger.kernel.org +Cc: Arnd Bergmann <arnd@arndb.de> |