From: Dave Jiang <dave.jiang@xxxxxxxxx>
The numa_emulation() routine in the 'uniform' case walks through all the
physical 'memblk' instances and divides them into N emulated nodes with
split_nodes_size_interleave_uniform(). As each physical node is consumed
it is removed from the physical memblk array in the
numa_remove_memblk_from() helper. Since
split_nodes_size_interleave_uniform() handles advancing the array as the
'memblk' is consumed it is expected that the base of the array is always
specified as the argument.
Otherwise, on multi-socket (> 2) configurations the uniform-split
capability can generate an invalid numa configuration leading to boot
failures with signatures like the following:
rcu: INFO: rcu_sched detected stalls on CPUs/tasks:
Sending NMI from CPU 0 to CPUs 2:
NMI backtrace for cpu 2
CPU: 2 PID: 1332 Comm: pgdatinit0 Not tainted 4.19.0-rc8-next-20181019-baseline #59
RIP: 0010:__init_single_page.isra.74+0x81/0x90
[..]
Call Trace:
deferred_init_pages+0xaa/0xe3
deferred_init_memmap+0x18f/0x318
kthread+0xf8/0x130
? deferred_free_pages.isra.105+0xc9/0xc9
? kthread_stop+0x110/0x110
ret_from_fork+0x35/0x40
Cc: x86@xxxxxxxxxx
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 1f6a2c6d9f121 ("x86/numa_emulation: Introduce uniform split capability")
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Tested-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
Changes since v2: https://lore.kernel.org/patchwork/patch/988541/
* Update the changelog with details from testing by Alex
arch/x86/mm/numa_emulation.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/numa_emulation.c b/arch/x86/mm/numa_emulation.c
index b54d52a2d00a..d71d72cf6c66 100644
--- a/arch/x86/mm/numa_emulation.c
+++ b/arch/x86/mm/numa_emulation.c
@@ -400,9 +400,17 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt)
n = simple_strtoul(emu_cmdline, &emu_cmdline, 0);
ret = -1;
for_each_node_mask(i, physnode_mask) {
+ /*
+ * The reason we pass in blk[0] is due to
+ * numa_remove_memblk_from() called by
+ * emu_setup_memblk() will delete entry 0
+ * and then move everything else up in the pi.blk
+ * array. Therefore we should always be looking
+ * at blk[0].
+ */
ret = split_nodes_size_interleave_uniform(&ei, &pi,
- pi.blk[i].start, pi.blk[i].end, 0,
- n, &pi.blk[i], nid);
+ pi.blk[0].start, pi.blk[0].end, 0,
+ n, &pi.blk[0], nid);
if (ret < 0)
break;
if (ret < n) {
