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From:   Jia He <justin.he@arm.com>
To:     Dan Williams <dan.j.williams@intel.com>,
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        Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
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        Jia He <justin.he@arm.com>
Subject: [RFC PATCH 6/6] arm64: fall back to vmemmap_populate_basepages if not aligned  with PMD_SIZE
Date:   Wed, 29 Jul 2020 11:34:24 +0800
Message-Id: <20200729033424.2629-7-justin.he@arm.com>
In-Reply-To: <20200729033424.2629-1-justin.he@arm.com>
References: <20200729033424.2629-1-justin.he@arm.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

In dax pmem kmem (dax pmem used as RAM device) case, the start address
might not be aligned with PMD_SIZE
e.g.
240000000-33fdfffff : Persistent Memory
  240000000-2421fffff : namespace0.0
  242400000-2bfffffff : dax0.0
    242400000-2bfffffff : System RAM (kmem)
pfn_to_page(0x242400000) is fffffe0007e90000.

Without this patch, vmemmap_populate(fffffe0007e90000, ...) will incorrectly
create a pmd mapping [fffffe0007e00000, fffffe0008000000] which contains
fffffe0007e90000.

This adds the check and then falls back to vmemmap_populate_basepages()

Signed-off-by: Jia He <justin.he@arm.com>
---
 arch/arm64/mm/mmu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index d69feb2cfb84..3b21bd47e801 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1102,6 +1102,10 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 
 	do {
 		next = pmd_addr_end(addr, end);
+		if (next - addr < PMD_SIZE) {
+			vmemmap_populate_basepages(start, next, node, altmap);
+			continue;
+		}
 
 		pgdp = vmemmap_pgd_populate(addr, node);
 		if (!pgdp)
-- 
2.17.1