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SubjectRe: [PATCH] Fix early panic issue on machines with memless node
On Tue, 5 May 2009, Zhang, Yanmin wrote:

> Kernel 2.6.30-rc4 panic with boot parameter mem=2G on Nehalem machine.
> The machines has 2 nodes and every node has about 3G memory.
>
> Alex Shi did a good bisect and located the bad patch.
>
> commit dc098551918093901d8ac8936e9d1a1b891b56ed
> Author: Jack Steiner <steiner@sgi.com>
> Date: Fri Apr 17 09:22:42 2009 -0500
>
> x86/uv: fix init of memory-less nodes
>
> Add support for nodes that have cpus but no memory.
> The current code was failing to add these nodes
> to the nodes_present_map.
>
> v2: Fixes case caught by David Rientjes - missed support
> for the x2apic SRAT table.
>
> [ Impact: fix potential boot crash on memory-less UV nodes. ]
>
> Reported-by: David Rientjes <rientjes@google.com>
> Signed-off-by: Jack Steiner <steiner@sgi.com>
> LKML-Reference: <20090417142242.GA23743@sgi.com>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
>
>
>
> With earlyprintk boot parameter, we captured below dump info.
>
> <6>bootmem::alloc_bootmem_core nid=0 size=0 [0 pages] align=1000 goal=1000000 lim0
> PANIC: early exception 06 rip 10:ffffffff80a2fbe4 error 0 cr2 0
> Pid: 0, comm: swapper Not tainted 2.6.30-rc4-ymz #3
> Call Trace:
> [<ffffffff80a1a195>] ? early_idt_handler+0x55/0x68
> [<ffffffff80a2fbe4>] ? alloc_bootmem_core+0x91/0x2ae
> [<ffffffff80a2fbdc>] ? alloc_bootmem_core+0x89/0x2ae
> [<ffffffff80a2fe74>] ? ___alloc_bootmem_nopanic+0x73/0xab
> [<ffffffff80a2af73>] ? early_node_mem+0x54/0x78
> [<ffffffff80a2b0ed>] ? setup_node_bootmem+0x156/0x282
> [<ffffffff80a2b880>] ? acpi_scan_nodes+0x207/0x303
> [<ffffffff80a2b255>] ? initmem_init+0x3c/0x14c
> [<ffffffff80a1e33b>] ? setup_arch+0x5ba/0x760
> [<ffffffff80a2e904>] ? cgroup_init_subsys+0xfc/0x105
> [<ffffffff80a2ea5f>] ? cgroup_init_early+0x152/0x163
> [<ffffffff80a1a915>] ? start_kernel+0x84/0x35e
> [<ffffffff80a1a37e>] ? x86_64_start_kernel+0xe5/0xeb
> RIP alloc_bootmem_core+0x91/0x2ae
>
> Consider below call chain:
> acpi_scan_nodes =>
> setup_node_bootmem
>  (twice) => early_node_mem
>
> At begining, acpi_scan_nodes filters out memless nodes by calling
> unparse_node. Patch dc098551918 adds the node back actually.
> acpi_scan_nodes has many comments around unparse_node.
>
> Below patch fixes it with node memory checking. Another method is just
> to revert the bad patch.
>
> David Rientjes, Jack Steiner,
> Would you check if below patch satisfy your original objective?
>

Could you try this instead?


srat: do not register nodes beyond e820 map

The mem= option will truncate the memory map at a specified address so
it's not possible to register nodes with memory beyond the e820 upper
bound.

unparse_node() is only called when then node had memory associated with
it, although with the mem= option it is no longer addressable.

Signed-off-by: David Rientjes <rientjes@google.com>
---
diff --git a/arch/x86/mm/srat_64.c b/arch/x86/mm/srat_64.c
--- a/arch/x86/mm/srat_64.c
+++ b/arch/x86/mm/srat_64.c
@@ -361,6 +361,7 @@ static void __init unparse_node(int node)
{
int i;
node_clear(node, nodes_parsed);
+ node_clear(node, cpu_nodes_parsed);
for (i = 0; i < MAX_LOCAL_APIC; i++) {
if (apicid_to_node[i] == node)
apicid_to_node[i] = NUMA_NO_NODE;
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