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From: Logan Gunthorpe <logang@deltatee.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	akpm@linux-foundation.org, will.deacon@arm.com,
	catalin.marinas@arm.com
Cc: mhocko@suse.com, mgorman@techsingularity.net,
	james.morse@arm.com, mark.rutland@arm.com, robin.murphy@arm.com,
	cpandya@codeaurora.org, arunks@codeaurora.org,
	dan.j.williams@intel.com, osalvador@suse.de,
	pasha.tatashin@oracle.com, david@redhat.com, cai@lca.pw,
	Stephen Bates <sbates@raithlin.com>
Subject: Re: [PATCH 2/6] arm64/mm: Enable memory hot remove
Date: Wed, 3 Apr 2019 11:32:51 -0600	[thread overview]
Message-ID: <f2ea761c-49b2-88f6-14fa-5aaec57952cb@deltatee.com> (raw)
In-Reply-To: <1554265806-11501-3-git-send-email-anshuman.khandual@arm.com>



On 2019-04-02 10:30 p.m., Anshuman Khandual wrote:
> Memory removal from an arch perspective involves tearing down two different
> kernel based mappings i.e vmemmap and linear while releasing related page
> table pages allocated for the physical memory range to be removed.
> 
> Define a common kernel page table tear down helper remove_pagetable() which
> can be used to unmap given kernel virtual address range. In effect it can
> tear down both vmemap or kernel linear mappings. This new helper is called
> from both vmemamp_free() and ___remove_pgd_mapping() during memory removal.
> The argument 'direct' here identifies kernel linear mappings.
> 
> Vmemmap mappings page table pages are allocated through sparse mem helper
> functions like vmemmap_alloc_block() which does not cycle the pages through
> pgtable_page_ctor() constructs. Hence while removing it skips corresponding
> destructor construct pgtable_page_dtor().
> 
> While here update arch_add_mempory() to handle __add_pages() failures by
> just unmapping recently added kernel linear mapping. Now enable memory hot
> remove on arm64 platforms by default with ARCH_ENABLE_MEMORY_HOTREMOVE.
> 
> This implementation is overall inspired from kernel page table tear down
> procedure on X86 architecture.

I've been working on very similar things for RISC-V. In fact, I'm
currently in progress on a very similar stripped down version of
remove_pagetable(). (Though I'm fairly certain I've done a bunch of
stuff wrong.)

Would it be possible to move this work into common code that can be used
by all arches? Seems like, to start, we should be able to support both
arm64 and RISC-V... and maybe even x86 too.

I'd be happy to help integrate and test such functions in RISC-V.

Thanks,

Logan



  parent reply	other threads:[~2019-04-03 17:33 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-03  4:30 [PATCH 0/6] arm64/mm: Enable memory hot remove and ZONE_DEVICE Anshuman Khandual
2019-04-03  4:30 ` [PATCH 1/6] arm64/mm: Enable sysfs based memory hot add interface Anshuman Khandual
2019-04-03  8:20   ` David Hildenbrand
2019-04-03 13:12     ` Robin Murphy
2019-04-04  5:21       ` Anshuman Khandual
2019-04-04  5:25     ` Anshuman Khandual
2019-04-04  8:49       ` David Hildenbrand
2019-04-03  4:30 ` [PATCH 2/6] arm64/mm: Enable memory hot remove Anshuman Khandual
2019-04-03 12:37   ` Robin Murphy
2019-04-03 13:15     ` Steven Price
2019-04-04  6:51       ` Anshuman Khandual
2019-04-04  5:39     ` Anshuman Khandual
2019-04-04 11:58       ` Oscar Salvador
2019-04-04 13:03         ` Anshuman Khandual
2019-04-04 15:19           ` Oscar Salvador
2019-04-03 17:32   ` Logan Gunthorpe [this message]
2019-04-03 17:57     ` Robin Murphy
2019-04-04  8:23       ` Anshuman Khandual
2019-04-04  7:07     ` Anshuman Khandual
2019-04-04  9:16       ` Steven Price
2019-04-03  4:30 ` [PATCH 3/6] arm64/mm: Enable struct page allocation from device memory Anshuman Khandual
2019-04-03  4:30 ` [PATCH 4/6] mm/hotplug: Reorder arch_remove_memory() call in __remove_memory() Anshuman Khandual
2019-04-03  8:45   ` Oscar Salvador
2019-04-03  9:17   ` Michal Hocko
2019-04-04  8:32     ` Anshuman Khandual
2019-04-03  9:30   ` David Hildenbrand
2019-04-03  4:30 ` [PATCH 5/6] mm/memremap: Rename and consolidate SECTION_SIZE Anshuman Khandual
2019-04-03  9:26   ` Michal Hocko
2019-04-03  9:30   ` David Hildenbrand
2019-04-03  4:30 ` [PATCH 6/6] arm64/mm: Enable ZONE_DEVICE Anshuman Khandual
2019-04-03 13:58   ` Robin Murphy
2019-04-03 16:07     ` Jerome Glisse
2019-04-04  5:03       ` Anshuman Khandual
2019-04-04  4:42     ` Anshuman Khandual
2019-04-04  5:04       ` Dan Williams
2019-04-04  9:46         ` Robin Murphy
2019-04-07 22:11           ` Dan Williams
2019-04-08  4:03             ` Ira Weiny
2019-04-08  6:03               ` Anshuman Khandual
2019-04-03 18:08 ` [PATCH 0/6] arm64/mm: Enable memory hot remove and ZONE_DEVICE Dan Williams
2019-04-04 13:11   ` Anshuman Khandual
2019-04-04  9:46 ` [RFC 1/2] mm/vmemmap: Enable vmem_altmap based base page mapping for vmemmap Anshuman Khandual
2019-04-04  9:46   ` [RFC 2/2] arm64/mm: Enable ZONE_DEVICE for all page configs Anshuman Khandual

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