linux-kernel - [PATCH 1/3] of: ignore sub-page memory regions

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Message-Id: <1530710295-10774-2-git-send-email-rppt@linux.vnet.ibm.com>
Date:   Wed,  4 Jul 2018 16:18:13 +0300
From:   Mike Rapoport <rppt@...ux.vnet.ibm.com>
To:     Ley Foon Tan <lftan@...era.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Michal Hocko <mhocko@...nel.org>,
        nios2-dev@...ts.rocketboards.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: [PATCH 1/3] of: ignore sub-page memory regions

Memory region size is rounded down to page boundary and with sub-page
region it becomes 0 and there is no point to add an empty region.
Moreover, when the base is less than PAGE_SIZE we get a bogus size as
(base + size - 1) evaluates to -1.

The commit 8cccffc52694 ("of: check for size < 0 after rounding in
early_init_dt_add_memory_arch") introduced a test for wrap around for the
case when base is not page aligned, the same test can be used to ignore
sub-page region sizes.

Signed-off-by: Mike Rapoport <rppt@...ux.vnet.ibm.com>
---
 drivers/of/fdt.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 6da20b9..e866745 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1134,12 +1134,13 @@ void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
 {
 	const u64 phys_offset = MIN_MEMBLOCK_ADDR;
 
+	if (size < PAGE_SIZE - (base & ~PAGE_MASK)) {
+		pr_warn("Ignoring memory block 0x%llx - 0x%llx\n",
+			base, base + size);
+		return;
+	}
+
 	if (!PAGE_ALIGNED(base)) {
-		if (size < PAGE_SIZE - (base & ~PAGE_MASK)) {
-			pr_warn("Ignoring memory block 0x%llx - 0x%llx\n",
-				base, base + size);
-			return;
-		}
 		size -= PAGE_SIZE - (base & ~PAGE_MASK);
 		base = PAGE_ALIGN(base);
 	}
-- 
2.7.4