[PATCH 1/4] RISC-V: Do not allocate memblock while iterating reserved memblocks

From: Atish Patra
Date: Thu Jan 07 2021 - 04:29:34 EST


Currently, resource tree allocates memory blocks while iterating on the
list. It leads to following kernel warning because memblock allocation
also invokes memory block reservation API.

[ 0.000000] ------------[ cut here ]------------
[ 0.000000] WARNING: CPU: 0 PID: 0 at kernel/resource.c:795
__insert_resource+0x8e/0xd0
[ 0.000000] Modules linked in:
[ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
5.10.0-00022-ge20097fb37e2-dirty #549
[ 0.000000] epc: c00125c2 ra : c001262c sp : c1c01f50
[ 0.000000] gp : c1d456e0 tp : c1c0a980 t0 : ffffcf20
[ 0.000000] t1 : 00000000 t2 : 00000000 s0 : c1c01f60
[ 0.000000] s1 : ffffcf00 a0 : ffffff00 a1 : c1c0c0c4
[ 0.000000] a2 : 80c12b15 a3 : 80402000 a4 : 80402000
[ 0.000000] a5 : c1c0c0c4 a6 : 80c12b15 a7 : f5faf600
[ 0.000000] s2 : c1c0c0c4 s3 : c1c0e000 s4 : c1009a80
[ 0.000000] s5 : c1c0c000 s6 : c1d48000 s7 : c1613b4c
[ 0.000000] s8 : 00000fff s9 : 80000200 s10: c1613b40
[ 0.000000] s11: 00000000 t3 : c1d4a000 t4 : ffffffff

This is also unnecessary as we can pre-compute the total memblocks required
for each memory region and allocate it before the loop. It save precious
boot time not going through memblock allocation code every time.

Fixes: 00ab027a3b82 ("RISC-V: Add kernel image sections to the resource tree")

Signed-off-by: Atish Patra <atish.patra@xxxxxxx>
---
arch/riscv/kernel/setup.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 1d85e9bf783c..3fa3f26dde85 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -127,7 +127,9 @@ static void __init init_resources(void)
{
struct memblock_region *region = NULL;
struct resource *res = NULL;
- int ret = 0;
+ struct resource *mem_res = NULL;
+ size_t mem_res_sz = 0;
+ int ret = 0, i = 0;

code_res.start = __pa_symbol(_text);
code_res.end = __pa_symbol(_etext) - 1;
@@ -145,16 +147,17 @@ static void __init init_resources(void)
bss_res.end = __pa_symbol(__bss_stop) - 1;
bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;

+ mem_res_sz = (memblock.memory.cnt + memblock.reserved.cnt) * sizeof(*mem_res);
+ mem_res = memblock_alloc(mem_res_sz, SMP_CACHE_BYTES);
+ if (!mem_res)
+ panic("%s: Failed to allocate %zu bytes\n", __func__, mem_res_sz);
/*
* Start by adding the reserved regions, if they overlap
* with /memory regions, insert_resource later on will take
* care of it.
*/
for_each_reserved_mem_region(region) {
- res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
- if (!res)
- panic("%s: Failed to allocate %zu bytes\n", __func__,
- sizeof(struct resource));
+ res = &mem_res[i++];

res->name = "Reserved";
res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
@@ -171,8 +174,10 @@ static void __init init_resources(void)
* Ignore any other reserved regions within
* system memory.
*/
- if (memblock_is_memory(res->start))
+ if (memblock_is_memory(res->start)) {
+ memblock_free((phys_addr_t) res, sizeof(struct resource));
continue;
+ }

ret = add_resource(&iomem_resource, res);
if (ret < 0)
@@ -181,10 +186,7 @@ static void __init init_resources(void)

/* Add /memory regions to the resource tree */
for_each_mem_region(region) {
- res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
- if (!res)
- panic("%s: Failed to allocate %zu bytes\n", __func__,
- sizeof(struct resource));
+ res = &mem_res[i++];

if (unlikely(memblock_is_nomap(region))) {
res->name = "Reserved";
@@ -205,9 +207,9 @@ static void __init init_resources(void)
return;

error:
- memblock_free((phys_addr_t) res, sizeof(struct resource));
/* Better an empty resource tree than an inconsistent one */
release_child_resources(&iomem_resource);
+ memblock_free((phys_addr_t) mem_res, mem_res_sz);
}


--
2.25.1