linux-kernel - [PATCH] powerpc: align memory_limit to 16MB in early_parse

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Date: Fri,  1 Mar 2024 15:30:23 -0500
From: Joel Savitz <jsavitz@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Joel Savitz <jsavitz@...hat.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"Aneesh Kumar K.V" <aneesh.kumar@...nel.org>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Benjamin Gray <bgray@...ux.ibm.com>,
	Paul Mackerras <paulus@...abs.org>,
	linuxppc-dev@...ts.ozlabs.org,
	Gonzalo Siero <gsierohu@...hat.com>
Subject: [PATCH] powerpc: align memory_limit to 16MB in early_parse_mem

On 64-bit powerpc, usage of a non-16MB-aligned value for the mem= kernel
cmdline parameter results in a system hang at boot.

For example, using 'mem=4198400K' will always reproduce this issue.

This patch fixes the problem by aligning any argument to mem= to 16MB
corresponding with the large page size on powerpc.

Fixes: 2babf5c2ec2f ("[PATCH] powerpc: Unify mem= handling")
Co-developed-by: Gonzalo Siero <gsierohu@...hat.com>
Signed-off-by: Gonzalo Siero <gsierohu@...hat.com>
Signed-off-by: Joel Savitz <jsavitz@...hat.com>
---
 arch/powerpc/kernel/prom.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 0b5878c3125b..8cd3e2445d8a 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -82,8 +82,12 @@ static int __init early_parse_mem(char *p)
 {
 	if (!p)
 		return 1;
-
+#ifdef CONFIG_PPC64
+	/* Align to 16 MB == size of ppc64 large page */
+	memory_limit = ALIGN(memparse(p, &p), 0x1000000);
+#else
 	memory_limit = PAGE_ALIGN(memparse(p, &p));
+#endif
 	DBG("memory limit = 0x%llx\n", memory_limit);
 
 	return 0;
-- 
2.43.0