linux-kernel - [PATCH v3 04/11] arm64/mm: Add temporary arch_remove

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

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@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Chintan Pandya <cpandya@...eaurora.org>
Cc: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Jun Yao <yaojun8558363@...il.com>
Cc: Yu Zhao <yuzhao@...gle.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Anshuman Khandual <anshuman.khandual@....com>
Signed-off-by: David Hildenbrand <david@...hat.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