[PATCH v5 1/2] RISC-V: Fix memory reservation in setup_bootmem()

[Anup Patel]

Currently, the setup_bootmem() reserves memory from RAM start to the
kernel end. This prevents us from exploring ways to use the RAM below
(or before) the kernel start hence this patch updates setup_bootmem()
to only reserve memory from the kernel start to the kernel end.

Suggested-by: Mike Rapoport <r...@linux.ibm.com>
Signed-off-by: Anup Patel <anup.pa...@wdc.com>
Reviewed-by: Christoph Hellwig <h...@lst.de>
---
 arch/riscv/mm/init.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 8bf6f9c2d48c..1879501bd156 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -29,6 +29,8 @@ unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned 
long)]
                                                        __page_aligned_bss;
 EXPORT_SYMBOL(empty_zero_page);
 
+extern char _start[];
+
 static void __init zone_sizes_init(void)
 {
        unsigned long max_zone_pfns[MAX_NR_ZONES] = { 0, };
@@ -103,18 +105,14 @@ void __init setup_bootmem(void)
 {
        struct memblock_region *reg;
        phys_addr_t mem_size = 0;
+       phys_addr_t vmlinux_end = __pa(&_end);
+       phys_addr_t vmlinux_start = __pa(&_start);
 
        /* Find the memory region containing the kernel */
        for_each_memblock(memory, reg) {
-               phys_addr_t vmlinux_end = __pa(_end);
                phys_addr_t end = reg->base + reg->size;
 
                if (reg->base <= vmlinux_end && vmlinux_end <= end) {
-                       /*
-                        * Reserve from the start of the region to the end of
-                        * the kernel
-                        */
-                       memblock_reserve(reg->base, vmlinux_end - reg->base);
                        mem_size = min(reg->size, (phys_addr_t)-PAGE_OFFSET);
 
                        /*
@@ -128,6 +126,9 @@ void __init setup_bootmem(void)
        }
        BUG_ON(mem_size == 0);
 
+       /* Reserve from the start of the kernel to the end of the kernel */
+       memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
+
        set_max_mapnr(PFN_DOWN(mem_size));
        max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());
 
@@ -205,7 +206,6 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t 
phys, pgprot_t prot)
 
 asmlinkage void __init setup_vm(void)
 {
-       extern char _start;
        uintptr_t i;
        uintptr_t pa = (uintptr_t) &_start;
        pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC);
-- 
2.17.1