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From:   Mike Rapoport <rppt@kernel.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Greg Kurz <gkurz@redhat.com>, Mike Rapoport <rppt@kernel.org>,
        Mike Rapoport <rppt@linux.ibm.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] memblock: make for_each_mem_range() traverse MEMBLOCK_HOTPLUG regions
Date:   Mon, 12 Jul 2021 10:11:32 +0300
Message-Id: <20210712071132.20902-1-rppt@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

From: Mike Rapoport <rppt@linux.ibm.com>

Commit b10d6bca8720 ("arch, drivers: replace for_each_membock() with
for_each_mem_range()") didn't take into account that when there is
movable_node parameter in the kernel command line, for_each_mem_range()
would skip ranges marked with MEMBLOCK_HOTPLUG.

The page table setup code in POWER uses for_each_mem_range() to create the
linear mapping of the physical memory and since the regions marked as
MEMORY_HOTPLUG are skipped, they never make it to the linear map.

A later access to the memory in those ranges will fail:

[    2.271743] BUG: Unable to handle kernel data access on write at 0xc000000400000000
[    2.271984] Faulting instruction address: 0xc00000000008a3c0
[    2.272568] Oops: Kernel access of bad area, sig: 11 [#1]
[    2.272683] LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
[    2.273063] Modules linked in:
[    2.273435] CPU: 0 PID: 53 Comm: kworker/u2:0 Not tainted 5.13.0 #7
[    2.273832] NIP:  c00000000008a3c0 LR: c0000000003c1ed8 CTR: 0000000000000040
[    2.273918] REGS: c000000008a57770 TRAP: 0300   Not tainted  (5.13.0)
[    2.274036] MSR:  8000000002009033 <SF,VEC,EE,ME,IR,DR,RI,LE>  CR: 84222202  XER: 20040000
[    2.274454] CFAR: c0000000003c1ed4 DAR: c000000400000000 DSISR: 42000000 IRQMASK: 0
[    2.274454] GPR00: c0000000003c1ed8 c000000008a57a10 c0000000019da700 c000000400000000
[    2.274454] GPR04: 0000000000000280 0000000000000180 0000000000000400 0000000000000200
[    2.274454] GPR08: 0000000000000100 0000000000000080 0000000000000040 0000000000000300
[    2.274454] GPR12: 0000000000000380 c000000001bc0000 c0000000001660c8 c000000006337e00
[    2.274454] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
[    2.274454] GPR20: 0000000040000000 0000000020000000 c000000001a81990 c000000008c30000
[    2.274454] GPR24: c000000008c20000 c000000001a81998 000fffffffff0000 c000000001a819a0
[    2.274454] GPR28: c000000001a81908 c00c000001000000 c000000008c40000 c000000008a64680
[    2.275520] NIP [c00000000008a3c0] clear_user_page+0x50/0x80
[    2.276333] LR [c0000000003c1ed8] __handle_mm_fault+0xc88/0x1910
[    2.276688] Call Trace:
[    2.276839] [c000000008a57a10] [c0000000003c1e94] __handle_mm_fault+0xc44/0x1910 (unreliable)
[    2.277142] [c000000008a57af0] [c0000000003c2c90] handle_mm_fault+0x130/0x2a0
[    2.277331] [c000000008a57b40] [c0000000003b5f08] __get_user_pages+0x248/0x610
[    2.277541] [c000000008a57c40] [c0000000003b848c] __get_user_pages_remote+0x12c/0x3e0
[    2.277768] [c000000008a57cd0] [c000000000473f24] get_arg_page+0x54/0xf0
[    2.277959] [c000000008a57d10] [c000000000474a7c] copy_string_kernel+0x11c/0x210
[    2.278159] [c000000008a57d80] [c00000000047663c] kernel_execve+0x16c/0x220
[    2.278361] [c000000008a57dd0] [c000000000166270] call_usermodehelper_exec_async+0x1b0/0x2f0
[    2.278543] [c000000008a57e10] [c00000000000d5ec] ret_from_kernel_thread+0x5c/0x70
[    2.278870] Instruction dump:
[    2.279214] 79280fa4 79271764 79261f24 794ae8e2 7ca94214 7d683a14 7c893a14 7d893050
[    2.279416] 7d4903a6 60000000 60000000 60000000 <7c001fec> 7c091fec 7c081fec 7c051fec
[    2.280193] ---[ end trace 490b8c67e6075e09 ]---

Making for_each_mem_range() include MEMBLOCK_HOTPLUG regions in the
traversal fixes this issue.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1976100
Fixes: b10d6bca8720 ("arch, drivers: replace for_each_membock() with for_each_mem_range()")
Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
 include/linux/memblock.h | 4 ++--
 mm/memblock.c            | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/memblock.h b/include/linux/memblock.h
index cbf46f56d105..4a53c3ca86bd 100644
--- a/include/linux/memblock.h
+++ b/include/linux/memblock.h
@@ -209,7 +209,7 @@ static inline void __next_physmem_range(u64 *idx, struct memblock_type *type,
  */
 #define for_each_mem_range(i, p_start, p_end) \
 	__for_each_mem_range(i, &memblock.memory, NULL, NUMA_NO_NODE,	\
-			     MEMBLOCK_NONE, p_start, p_end, NULL)
+			     MEMBLOCK_HOTPLUG, p_start, p_end, NULL)
 
 /**
  * for_each_mem_range_rev - reverse iterate through memblock areas from
@@ -220,7 +220,7 @@ static inline void __next_physmem_range(u64 *idx, struct memblock_type *type,
  */
 #define for_each_mem_range_rev(i, p_start, p_end)			\
 	__for_each_mem_range_rev(i, &memblock.memory, NULL, NUMA_NO_NODE, \
-				 MEMBLOCK_NONE, p_start, p_end, NULL)
+				 MEMBLOCK_HOTPLUG, p_start, p_end, NULL)
 
 /**
  * for_each_reserved_mem_range - iterate over all reserved memblock areas
diff --git a/mm/memblock.c b/mm/memblock.c
index 0041ff62c584..de7b553baa50 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -947,7 +947,8 @@ static bool should_skip_region(struct memblock_type *type,
 		return true;
 
 	/* skip hotpluggable memory regions if needed */
-	if (movable_node_is_enabled() && memblock_is_hotpluggable(m))
+	if (movable_node_is_enabled() && memblock_is_hotpluggable(m) &&
+	    !(flags & MEMBLOCK_HOTPLUG))
 		return true;
 
 	/* if we want mirror memory skip non-mirror memory regions */

base-commit: e73f0f0ee7541171d89f2e2491130c7771ba58d3
-- 
2.28.0