linux-kernel - [PATCH] riscv: Add support for mem=

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Message-ID: <899dc26e-aca5-0a81-ccb5-c0fda59503f0@siemens.com>
Date:   Fri, 14 Feb 2020 16:33:48 +0100
From:   Jan Kiszka <jan.kiszka@...mens.com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-riscv@...ts.infradead.org
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] riscv: Add support for mem=

From: Jan Kiszka <jan.kiszka@...mens.com>

This sets a memory limit provided via mem= on the command line,
analogously to many other architectures.

Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>
---
 arch/riscv/mm/init.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 965a8cf4829c..09948e43741b 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -488,8 +488,26 @@ static inline void setup_vm_final(void)
 }
 #endif /* CONFIG_MMU */
 
+static phys_addr_t memory_limit = PHYS_ADDR_MAX;
+
+/*
+ * Limit the memory size that was specified via FDT.
+ */
+static int __init early_mem(char *p)
+{
+	if (!p)
+		return 1;
+
+	memory_limit = memparse(p, &p) & PAGE_MASK;
+	pr_notice("Memory limited to %lldMB\n", memory_limit >> 20);
+
+	return 0;
+}
+early_param("mem", early_mem);
+
 void __init paging_init(void)
 {
+	memblock_enforce_memory_limit(memory_limit);
 	setup_vm_final();
 	memblocks_present();
 	sparse_init();
-- 
2.16.4


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