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Commit ebb682f5 authored by Prarit Bhargava's avatar Prarit Bhargava Committed by H. Peter Anvin
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x86, AMD: Fix stale cpuid4_info shared_map data in shared_cpu_map cpumasks 



The per_cpu cpuid4_info shared_map can contain stale data when CPUs are added
and removed.

The stale data can lead to a NULL pointer derefernce panic on a remove of a
CPU that has had siblings previously removed.

This patch resolves the panic by verifying a cpu is actually online before
adding it to the shared_cpu_map, only examining cpus that are part of
the same lower level cache, and by updating other siblings lowest level cache
maps when a cpu is added.

Signed-off-by: default avatarPrarit Bhargava <prarit@redhat.com>
LKML-Reference: <20091209183336.17855.98708.sendpatchset@prarit.bos.redhat.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 9cf78267

arch/x86/kernel/cpu/intel_cacheinfo.c

+7 −6
Original line number Original line Diff line number Diff line
@@ -507,18 +507,19 @@ static void __cpuinit cache_shared_cpu_map_setup(unsigned int cpu, int index) 
{

{

	struct _cpuid4_info	*this_leaf, *sibling_leaf;

	struct _cpuid4_info	*this_leaf, *sibling_leaf;

	unsigned long num_threads_sharing;

	unsigned long num_threads_sharing;

	int index_msb, i;

	int index_msb, i, sibling;

	struct cpuinfo_x86 *c = &cpu_data(cpu);

	struct cpuinfo_x86 *c = &cpu_data(cpu);





	if ((index == 3) && (c->x86_vendor == X86_VENDOR_AMD)) {

	if ((index == 3) && (c->x86_vendor == X86_VENDOR_AMD)) {

		struct cpuinfo_x86 *d;

		for_each_cpu(i, c->llc_shared_map) {

		for_each_online_cpu(i) {

			if (!per_cpu(cpuid4_info, i))

			if (!per_cpu(cpuid4_info, i))

				continue;

				continue;

			d = &cpu_data(i);

			this_leaf = CPUID4_INFO_IDX(i, index);

			this_leaf = CPUID4_INFO_IDX(i, index);

			cpumask_copy(to_cpumask(this_leaf->shared_cpu_map),

			for_each_cpu(sibling, c->llc_shared_map) {

				     d->llc_shared_map);

				if (!cpu_online(sibling))

					continue;

				set_bit(sibling, this_leaf->shared_cpu_map);

			}

		}

		}

		return;

		return;

	}

	}