linux-kernel - [PATCH v2] x86/numa_emulation: fix parsing of numa

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Date:   Wed, 19 Sep 2018 11:12:14 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     mingo@...hat.com, dan.j.williams@...el.com
Cc:     tglx@...utronix.de, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] x86/numa_emulation: fix parsing of numa_meminfo for
 uniform numa emulation

During fakenuma processing in numa_emulation(), pi gets passed in and
processed as new fake numa nodes are being split out. Once the original
memory region is proccessed, it gets removed from the pi by
numa_remove_memblk_from() in emu_setup_memblk(). So entry 0 gets deleted
and the rest of the entries get moved up. Therefore we should always pass
in entry 0 for the next entry to process.

Fixes: 1f6a2c6d9f121 ("x86/numa_emulation: Introduce uniform split
capability")

Cc: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Dave Jiang <dave.jiang@...el.com>
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
---

V2:
- Add comment for the code change (Dan)

 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) {