x86/numa_emulation: Fix uniform-split numa emulation

davejiang · KAGA-KOKO · commit c6ee7a548e2c · 2018-10-30T11:36:43.000+01:00
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 torvalds#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 Fixes: 1f6a2c6d9f121 ("x86/numa_emulation: Introduce uniform split capability") Signed-off-by: Dave Jiang <dave.jiang@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Alexander Duyck <alexander.h.duyck@linux.intel.com> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/154049911459.2685845.9210186007479774286.stgit@dwillia2-desk3.amr.corp.intel.com
diff --git 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) {
