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SubjectRe: [PATCH 1/4] x86, amd: Normalize compute unit IDs on multi-node processors
On Mon, 24 Jan 2011 16:05:40 +0100
Hans Rosenfeld <hans.rosenfeld@amd.com> wrote:

> From: Andreas Herrmann <andreas.herrmann3@amd.com>
>
> On multi-node CPUs we don't need the socket wide compute unit ID but
> the node-wide compute unit ID. Thus we need to normalize the value.
> This is similar to what we do with cpu_core_id.
>
> A compute unit is then identified by physical_package_id, node_id, and
> compute_unit_id.
>
> ...
>
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -261,7 +261,7 @@ static int __cpuinit nearby_node(int apicid)
> #ifdef CONFIG_X86_HT
> static void __cpuinit amd_get_topology(struct cpuinfo_x86 *c)
> {
> - u32 nodes;
> + u32 nodes, cores_per_cu;
> u8 node_id;
> int cpu = smp_processor_id();
>
> @@ -276,6 +276,7 @@ static void __cpuinit amd_get_topology(struct cpuinfo_x86 *c)
> /* get compute unit information */
> smp_num_siblings = ((ebx >> 8) & 3) + 1;
> c->compute_unit_id = ebx & 0xff;
> + cores_per_cu = ((ebx >> 8) & 3) + 1;
> } else if (cpu_has(c, X86_FEATURE_NODEID_MSR)) {
> u64 value;
>
> @@ -288,15 +289,18 @@ static void __cpuinit amd_get_topology(struct cpuinfo_x86 *c)
> /* fixup multi-node processor information */
> if (nodes > 1) {
> u32 cores_per_node;
> + u32 cus_per_node;
>
> set_cpu_cap(c, X86_FEATURE_AMD_DCM);
> cores_per_node = c->x86_max_cores / nodes;
> + cus_per_node = cores_per_node / cores_per_cu;
>
> /* store NodeID, use llc_shared_map to store sibling info */
> per_cpu(cpu_llc_id, cpu) = node_id;
>
> /* core id to be in range from 0 to (cores_per_node - 1) */
> - c->cpu_core_id = c->cpu_core_id % cores_per_node;
> + c->cpu_core_id %= cores_per_node;
> + c->compute_unit_id %= cus_per_node;
> }
> }
> #endif

arch/x86/kernel/cpu/amd.c: In function 'init_amd':
arch/x86/kernel/cpu/amd.c:268: warning: 'cores_per_cu' may be used uninitialized in this function

The code looks buggy to me.


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