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SubjectRe: [PATCH V3 0/4] arm64/mm: Enable memory hot remove
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On 14.05.19 11:00, Anshuman Khandual wrote:
> This series enables memory hot remove on arm64 after fixing a memblock
> removal ordering problem in generic __remove_memory() and kernel page
> table race conditions on arm64. This is based on the following arm64
> working tree.
>
> git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
>
> David had pointed out that the following patch is already in next/master
> (58b11e136dcc14358) and will conflict with the last patch here. Will fix
> the conflict once this series gets reviewed and agreed upon.

I should read the cover letter first, so ignore my comments :)

>
> Author: David Hildenbrand <david@redhat.com>
> Date: Wed Apr 10 11:02:27 2019 +1000
>
> mm/memory_hotplug: make __remove_pages() and arch_remove_memory() never fail
>
> All callers of arch_remove_memory() ignore errors. And we should really
> try to remove any errors from the memory removal path. No more errors are
> reported from __remove_pages(). BUG() in s390x code in case
> arch_remove_memory() is triggered. We may implement that properly later.
> WARN in case powerpc code failed to remove the section mapping, which is
> better than ignoring the error completely right now.
>
> Testing:
>
> Tested memory hot remove on arm64 for 4K, 16K, 64K page config options with
> all possible CONFIG_ARM64_VA_BITS and CONFIG_PGTABLE_LEVELS combinations. But
> build tested on non arm64 platforms.
>
> Changes in V3:
>
> - Implemented most of the suggestions from Mark Rutland for remove_pagetable()
> - Fixed applicable PGTABLE_LEVEL wrappers around pgtable page freeing functions
> - Replaced 'direct' with 'sparse_vmap' in remove_pagetable() with inverted polarity
> - Changed pointer names ('p' at end) and removed tmp from iterations
> - Perform intermediate TLB invalidation while clearing pgtable entries
> - Dropped flush_tlb_kernel_range() in remove_pagetable()
> - Added flush_tlb_kernel_range() in remove_pte_table() instead
> - Renamed page freeing functions for pgtable page and mapped pages
> - Used page range size instead of order while freeing mapped or pgtable pages
> - Removed all PageReserved() handling while freeing mapped or pgtable pages
> - Replaced XXX_index() with XXX_offset() while walking the kernel page table
> - Used READ_ONCE() while fetching individual pgtable entries
> - Taken overall init_mm.page_table_lock instead of just while changing an entry
> - Dropped previously added [pmd|pud]_index() which are not required anymore
>
> - Added a new patch to protect kernel page table race condtion for ptdump
> - Added a new patch from Mark Rutland to prevent huge-vmap with ptdump
>
> Changes in V2: (https://lkml.org/lkml/2019/4/14/5)
>
> - Added all received review and ack tags
> - Split the series from ZONE_DEVICE enablement for better review
> - Moved memblock re-order patch to the front as per Robin Murphy
> - Updated commit message on memblock re-order patch per Michal Hocko
> - Dropped [pmd|pud]_large() definitions
> - Used existing [pmd|pud]_sect() instead of earlier [pmd|pud]_large()
> - Removed __meminit and __ref tags as per Oscar Salvador
> - Dropped unnecessary 'ret' init in arch_add_memory() per Robin Murphy
> - Skipped calling into pgtable_page_dtor() for linear mapping page table
> pages and updated all relevant functions
>
> Changes in V1: (https://lkml.org/lkml/2019/4/3/28)
>
> Anshuman Khandual (3):
> mm/hotplug: Reorder arch_remove_memory() call in __remove_memory()
> arm64/mm: Hold memory hotplug lock while walking for kernel page table dump
> arm64/mm: Enable memory hot remove
>
> Mark Rutland (1):
> arm64/mm: Inhibit huge-vmap with ptdump
>
> arch/arm64/Kconfig | 3 +
> arch/arm64/mm/mmu.c | 215 ++++++++++++++++++++++++++++++++++++++++-
> arch/arm64/mm/ptdump_debugfs.c | 3 +
> mm/memory_hotplug.c | 3 +-
> 4 files changed, 217 insertions(+), 7 deletions(-)
>


--

Thanks,

David / dhildenb

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