From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Date: Tue, 04 Jun 2019 06:56:15 +0000 Subject: Re: [PATCH v3 04/11] arm64/mm: Add temporary arch_remove_memory() implementation Message-Id: <5059f68d-45d2-784e-0770-ee67060773c7@redhat.com> List-Id: References: <20190527111152.16324-1-david@redhat.com> <20190527111152.16324-5-david@redhat.com> <20190603214139.mercn5hol2yyfl2s@master> In-Reply-To: <20190603214139.mercn5hol2yyfl2s@master> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Wei Yang Cc: Mark Rutland , linux-s390@vger.kernel.org, linux-ia64@vger.kernel.org, Yu Zhao , Anshuman Khandual , linux-sh@vger.kernel.org, Catalin Marinas , Ard Biesheuvel , Will Deacon , linux-kernel@vger.kernel.org, Mike Rapoport , Jun Yao , linux-mm@kvack.org, Chintan Pandya , Igor Mammedov , akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, Dan Williams , linux-arm-kernel@lists.infradead.org, Robin Murphy On 03.06.19 23:41, Wei Yang wrote: > On Mon, May 27, 2019 at 01:11:45PM +0200, David Hildenbrand wrote: >> A proper arch_remove_memory() implementation is on its way, which also >> cleanly removes page tables in arch_add_memory() in case something goes >> wrong. > > Would this be better to understand? > > removes page tables created in arch_add_memory That's not what this sentence expresses. Have a look at arch_add_memory(), in case __add_pages() fails, the page tables are not removed. This will also be fixed by Anshuman in the same shot. > >> >> As we want to use arch_remove_memory() in case something goes wrong >> during memory hotplug after arch_add_memory() finished, let's add >> a temporary hack that is sufficient enough until we get a proper >> implementation that cleans up page table entries. >> >> We will remove CONFIG_MEMORY_HOTREMOVE around this code in follow up >> patches. >> >> Cc: Catalin Marinas >> Cc: Will Deacon >> Cc: Mark Rutland >> Cc: Andrew Morton >> Cc: Ard Biesheuvel >> Cc: Chintan Pandya >> Cc: Mike Rapoport >> Cc: Jun Yao >> Cc: Yu Zhao >> Cc: Robin Murphy >> Cc: Anshuman Khandual >> Signed-off-by: David Hildenbrand >> --- >> arch/arm64/mm/mmu.c | 19 +++++++++++++++++++ >> 1 file changed, 19 insertions(+) >> >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index a1bfc4413982..e569a543c384 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -1084,4 +1084,23 @@ int arch_add_memory(int nid, u64 start, u64 size, >> return __add_pages(nid, start >> PAGE_SHIFT, size >> PAGE_SHIFT, >> restrictions); >> } >> +#ifdef CONFIG_MEMORY_HOTREMOVE >> +void arch_remove_memory(int nid, u64 start, u64 size, >> + struct vmem_altmap *altmap) >> +{ >> + unsigned long start_pfn = start >> PAGE_SHIFT; >> + unsigned long nr_pages = size >> PAGE_SHIFT; >> + struct zone *zone; >> + >> + /* >> + * FIXME: Cleanup page tables (also in arch_add_memory() in case >> + * adding fails). Until then, this function should only be used >> + * during memory hotplug (adding memory), not for memory >> + * unplug. ARCH_ENABLE_MEMORY_HOTREMOVE must not be >> + * unlocked yet. >> + */ >> + zone = page_zone(pfn_to_page(start_pfn)); > > Compared with arch_remove_memory in x86. If altmap is not NULL, zone will be > retrieved from page related to altmap. Not sure why this is not the same? This is a minimal implementation, sufficient for this use case here. A full implementation is in the works. For now, this function will not be used with an altmap (ZONE_DEVICE is not esupported for arm64 yet). Thanks! > >> + __remove_pages(zone, start_pfn, nr_pages, altmap); >> +} >> +#endif >> #endif >> -- >> 2.20.1 > -- Thanks, David / dhildenb