Re: [PATCH 10/26] x86-64, NUMA: Move apicid to numa mapping initializationfrom amd_scan_nodes() to amd_numa_init()

[Cyrill Gorcunov]

On 02/15/2011 12:36 PM, Tejun Heo wrote:
...
> >    Hi Tejun, while you at it, it seems apicid_base conditional assignment is
> > redundant here (boot_cpu_physical_apicid is unsigned int) so we might have
> > something like
> >
> > 	apicid_start	= boot_cpu_physical_apicid;
> > 	apicid_end	= apicid_start + cores;
> >
> > 	for_each_node_mask(i, cpu_nodes_parsed) {
> > 		for (j = apicid_start; j<   apicid_end; j++)
> > 			set_apicid_to_node((i<<   bits) + j, i);
> > 	}
>
> Right, I think the intention there was
>
> 	if (boot_cpu_physical_apicid == -1U)
>
> because that's the initial value and we don't really want to index the
> apicid nid table with -1U.  Care to send a patch?  I'm gonna have to
> rebase anyway and can put the patch at the front.
>
> Thanks.

 Hi Tejun again :) I've looked some more and if I'm not missing something
(Yinghai?) the code is broken in another way. We might have AMD system
with corrupted MADT table so boot_cpu_physical_apicid remains =-1U
and then we better BUG_ON instead of possible access of out-of-range
__apicid_to_node array. If MADT is parsed successfully boot_cpu_physical_apicid
will have correct value. So I think we rather should add something like the
patch below. Again better Yinghai check it first so I would not _miss_ the
point that such situation is impossible at all. (And if I'm right we need to
check for set_apicid_to_node(apicid, ) never exceed MAX_LOCAL_APIC as well.

Yinghai am I missing something?

--
    Cyrill

---
x86, numa: amd -- Check for screwed MADT table

In case if MADT table is corrupted we might end up
with boot_cpu_physical_apicid = -1U, corebits > 0 and
get out of __apicid_to_node array bound access. Check for
boot_cpu_physical_apicid being not default value.

Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
---
 arch/x86/mm/amdtopology_64.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Index: linux-2.6.git/arch/x86/mm/amdtopology_64.c
=====================================================================
--- linux-2.6.git.orig/arch/x86/mm/amdtopology_64.c
+++ linux-2.6.git/arch/x86/mm/amdtopology_64.c
@@ -271,9 +271,14 @@ int __init amd_scan_nodes(void)
 	bits = boot_cpu_data.x86_coreid_bits;
 	cores = (1<<bits);
 	apicid_base = 0;
+
 	/* get the APIC ID of the BSP early for systems with apicid lifting */
 	early_get_boot_cpu_id();
-	if (boot_cpu_physical_apicid > 0) {
+	if (boot_cpu_physical_apicid == -1U || ) {
+		pr_err("BAD APIC ID: %02x, NUMA node scaning canceled\n",
+			boot_cpu_physical_apicid);
+		return -1;
+	} else if (boot_cpu_physical_apicid > 0) {
 		pr_info("BSP APIC ID: %02x\n", boot_cpu_physical_apicid);
 		apicid_base = boot_cpu_physical_apicid;
 	}
--
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