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From: David Hildenbrand <david@redhat.com>
To: linux-mm@kvack.org
Subject: [PATCH v3 04/11] arm64/mm: Add temporary arch_remove_memory()
 implementation
Date: Mon, 27 May 2019 13:11:45 +0200
Message-Id: <20190527111152.16324-5-david@redhat.com>
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Cc: Mark Rutland <mark.rutland@arm.com>, linux-s390@vger.kernel.org,
 Ard Biesheuvel <ard.biesheuvel@linaro.org>, linux-ia64@vger.kernel.org,
 Yu Zhao <yuzhao@google.com>, Anshuman Khandual <anshuman.khandual@arm.com>,
 linux-sh@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>,
 David Hildenbrand <david@redhat.com>, Will Deacon <will.deacon@arm.com>,
 linux-kernel@vger.kernel.org, Wei Yang <richard.weiyang@gmail.com>,
 Jun Yao <yaojun8558363@gmail.com>, Chintan Pandya <cpandya@codeaurora.org>,
 Igor Mammedov <imammedo@redhat.com>, akpm@linux-foundation.org,
 Mike Rapoport <rppt@linux.ibm.com>, linuxppc-dev@lists.ozlabs.org,
 Dan Williams <dan.j.williams@intel.com>, linux-arm-kernel@lists.infradead.org,
 Robin Murphy <robin.murphy@arm.com>
Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

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.

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 <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Chintan Pandya <cpandya@codeaurora.org>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Cc: Jun Yao <yaojun8558363@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 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));
+	__remove_pages(zone, start_pfn, nr_pages, altmap);
+}
+#endif
 #endif
-- 
2.20.1