[PATCH v3] riscv: set max_pfn to the PFN of the last page

* [PATCH v3] riscv: set max_pfn to the PFN of the last page
@ 2020-04-27  6:59 Vincent Chen
  2020-05-04 21:13 ` Palmer Dabbelt
  0 siblings, 1 reply; 3+ messages in thread
From: Vincent Chen @ 2020-04-27  6:59 UTC (permalink / raw)
  To: paul.walmsley, palmer; +Cc: Vincent Chen, linux-riscv, stable

The current max_pfn equals to zero. In this case, I found it caused users
cannot get some page information through /proc such as kpagecount in v5.6
kernel because of new sanity checks. The following message is displayed by
stress-ng test suite with the command "stress-ng --verbose --physpage 1 -t
1" on HiFive unleashed board.

 # stress-ng --verbose --physpage 1 -t 1
 stress-ng: debug: [109] 4 processors online, 4 processors configured
 stress-ng: info: [109] dispatching hogs: 1 physpage
 stress-ng: debug: [109] cache allocate: reducing cache level from L3 (too high) to L0
 stress-ng: debug: [109] get_cpu_cache: invalid cache_level: 0
 stress-ng: info: [109] cache allocate: using built-in defaults as no suitable cache found
 stress-ng: debug: [109] cache allocate: default cache size: 2048K
 stress-ng: debug: [109] starting stressors
 stress-ng: debug: [109] 1 stressor spawned
 stress-ng: debug: [110] stress-ng-physpage: started [110] (instance 0)
 stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd34de000 in /proc/kpagecount, errno=0 (Success)
 stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd32db078 in /proc/kpagecount, errno=0 (Success)
 ...
 stress-ng: error: [110] stress-ng-physpage: cannot read page count for address 0x3fd32db078 in /proc/kpagecount, errno=0 (Success)
 stress-ng: debug: [110] stress-ng-physpage: exited [110] (instance 0)
 stress-ng: debug: [109] process [110] terminated
 stress-ng: info: [109] successful run completed in 1.00s
 #

After applying this patch, the kernel can pass the test.

 # stress-ng --verbose --physpage 1 -t 1
 stress-ng: debug: [104] 4 processors online, 4 processors configured stress-ng: info: [104] dispatching hogs: 1 physpage
 stress-ng: info: [104] cache allocate: using defaults, can't determine cache details from sysfs
 stress-ng: debug: [104] cache allocate: default cache size: 2048K
 stress-ng: debug: [104] starting stressors
 stress-ng: debug: [104] 1 stressor spawned
 stress-ng: debug: [105] stress-ng-physpage: started [105] (instance 0) stress-ng: debug: [105] stress-ng-physpage: exited [105] (instance 0) stress-ng: debug: [104] process [105] terminated
 stress-ng: info: [104] successful run completed in 1.01s
 #

Fixes: 0651c263c8e3 (RISC-V: Move setup_bootmem() to mm/init.c)
Cc: stable@vger.kernel.org

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Reviewed-by: Yash Shah <yash.shah@sifive.com>
Tested-by: Yash Shah <yash.shah@sifive.com>

Changes since v1:
1. Add Fixes line and Cc stable kernel
Changes since v2:
1. Fix typo in Anup email address
---
 arch/riscv/mm/init.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index fab855963c73..157924baa191 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -149,7 +149,8 @@ void __init setup_bootmem(void)
 	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
 
 	set_max_mapnr(PFN_DOWN(mem_size));
-	max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());
+	max_pfn = PFN_DOWN(memblock_end_of_DRAM());
+	max_low_pfn = max_pfn;
 
 #ifdef CONFIG_BLK_DEV_INITRD
 	setup_initrd();
-- 
2.7.4



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