x86/numa_emulation: Fix uniform-split numa emulation

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

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
index b54d52a..d71d72c 100644 (file)
--- 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) {