linux-kernel - [PATCH v2 1/3] riscv: Add support for mem=

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Date:   Sat, 15 Feb 2020 12:49:42 +0100
From:   Jan Kiszka <jan.kiszka@....de>
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@...r.kernel.org
Subject: [PATCH v2 1/3] 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 | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 965a8cf4829c..aec39a56d6cf 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -118,6 +118,23 @@ static void __init setup_initrd(void)
 }
 #endif /* CONFIG_BLK_DEV_INITRD */

+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);
+
 static phys_addr_t dtb_early_pa __initdata;

 void __init setup_bootmem(void)
@@ -127,6 +144,8 @@ void __init setup_bootmem(void)
 	phys_addr_t vmlinux_end = __pa_symbol(&_end);
 	phys_addr_t vmlinux_start = __pa_symbol(&_start);

+	memblock_enforce_memory_limit(memory_limit);
+
 	/* Find the memory region containing the kernel */
 	for_each_memblock(memory, reg) {
 		phys_addr_t end = reg->base + reg->size;
--
2.16.4