riscv: Add support for mem=

Commit Message

Jan Kiszka Feb. 14, 2020, 3:33 p.m. UTC

From: Jan Kiszka <[e-mail]>

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

Signed-off-by: Jan Kiszka <[e-mail]>
---
 arch/riscv/mm/init.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Patch

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();