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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Vincent Chen <vincent.chen@sifive.com>,
        Anup Patel <anup@brainfault.org>,
        Yash Shah <yash.shah@sifive.com>,
        Palmer Dabbelt <palmerdabbelt@google.com>
Subject: [PATCH 4.19 05/81] riscv: set max_pfn to the PFN of the last page
Date:   Tue, 26 May 2020 20:52:40 +0200
Message-Id: <20200526183924.534086347@linuxfoundation.org>
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From: Vincent Chen <vincent.chen@sifive.com>

commit c749bb2d554825e007cbc43b791f54e124dadfce upstream.

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
 #

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>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
[Palmer: back-ported to 4.19]
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/riscv/kernel/setup.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -19,6 +19,7 @@
  * to the Free Software Foundation, Inc.,
  */
 
+#include <linux/bootmem.h>
 #include <linux/init.h>
 #include <linux/mm.h>
 #include <linux/memblock.h>
@@ -187,6 +188,7 @@ static void __init setup_bootmem(void)
 
 	set_max_mapnr(PFN_DOWN(mem_size));
 	max_low_pfn = PFN_DOWN(memblock_end_of_DRAM());
+	max_pfn = max_low_pfn;
 
 #ifdef CONFIG_BLK_DEV_INITRD
 	setup_initrd();