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SubjectRe: [PATCH] x86, amd: Probe CPUs by APICID instead of initial APICID
On Tue, Apr 17, 2012 at 01:06:36PM +0300, Vlad Zolotarov wrote:
> From: Shai Fultheim <shai@scalemp.com>
>
> Make AMD identify processors using APICID (32 bit) rather than the initial
> APICID (8 bit). This is critical to make sure the last level cache (llc),
> which is used for sibling detection, will be different between boards - on
> aggregated systems with more than 8 processors.
>
>
> Signed-off-by: Shai Fultheim <shai@scalemp.com>
> Signed-off-by: Vlad Zolotarov <vlad@scalemp.com>

I think instead of fiddling with the generic code you rather should do
what was implemented for numascale support. See apic_numachip.c

Especially changing node_id will break other stuff.


> ---
> arch/x86/kernel/cpu/amd.c | 10 +++++-----
> 1 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 0bab2b1..33d9502 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -277,7 +277,7 @@ static void __cpuinit amd_get_topology(struct cpuinfo_x86 *c)
>
> cpuid(0x8000001e, &eax, &ebx, &ecx, &edx);
> nodes = ((ecx >> 8) & 7) + 1;
> - node_id = ecx & 7;
> + node_id = (ecx & 7) + (c->phys_proc_id << 3);
>
> /* get compute unit information */
> smp_num_siblings = ((ebx >> 8) & 3) + 1;
> @@ -288,7 +288,7 @@ static void __cpuinit amd_get_topology(struct cpuinfo_x86 *c)
>
> rdmsrl(MSR_FAM10H_NODE_ID, value);
> nodes = ((value >> 3) & 7) + 1;
> - node_id = value & 7;
> + node_id = (value & 7) + (c->phys_proc_id << 3);
> } else
> return;
>
> @@ -323,9 +323,9 @@ static void __cpuinit amd_detect_cmp(struct cpuinfo_x86 *c)
>
> bits = c->x86_coreid_bits;
> /* Low order bits define the core id (index of core in socket) */
> - c->cpu_core_id = c->initial_apicid & ((1 << bits)-1);
> - /* Convert the initial APIC ID into the socket ID */
> - c->phys_proc_id = c->initial_apicid >> bits;
> + c->cpu_core_id = c->apicid & ((1 << bits)-1);
> + /* Convert the APIC ID into the socket ID */
> + c->phys_proc_id = c->apicid >> bits;

Extracting phys_proc_id from apicid will result in wrong socket
enumeration on several systems. E.g. they would start with package_id
1 instead of 0.


Thanks,

Andreas




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