Messages in this thread Patch in this message |  | | | Date | Fri, 16 Jan 2009 15:22:16 -0800 | | From | Mike Travis <> | | Subject | [PATCH] x86: put trigger in to detect mismatched apic versions. |
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Ingo Molnar wrote: > * Mike Travis <travis@sgi.com> wrote: > >> Hi Ingo, >> >> I did notice that the versions all came up the same, and that the checks >> were very specific. I was trying to be as transparent and unintrusive >> as possible. Since there's so few calls, I though this was a good >> approach but apparently I was wrong. >> >> I like the idea of collapsing the array down to one and checking to see >> if all apic's have the same version, but is this really the case? Must >> all apics be the same? > > Could you please send a patch that doesnt change the code, only adds a > 'boot APIC version' kind of variable as an apic_version __read_mostly > variable and does a WARN_ONCE() if that mismatches? We can then stick that > into -tip and see whether it triggers. > > The max array size is ~128K, right? So if the WARN_ONCE() does not > trigger, we can just drop the array and use the central apic_version > variable ... > > And even if it _does_ trigger, the version incompatibilities between APIC > protocols are very rare. They only happen across wildly different CPU > architectures like when going from very old external apics to integrated > apics, or going from apics to x-apics. We wont see any mixing across those > boundaries. > > Ingo
Btw, I checked with our UV architect and the problem is that we need a 16 bit apic id which is what caused the MAX_APICS to be bumped to 32k. The lower 8 bits are the normal apic id, and the upper bit relate to the node. This means cpu 0 on node 0 has the same apic id as cpu 0 on node 1, etc. I also asked about whether we could rely on always having the same apic version, and the answer was yes, though it's really only relevant between the cpus on a node.
Thanks, Mike --- Subject: x86: put trigger in to detect mismatched apic versions. Fire off one message if two apic's discovered with different apic versions.
Signed-off-by: Mike Travis <travis@sgi.com> --- arch/x86/kernel/apic.c | 5 +++++ 1 file changed, 5 insertions(+) --- linux-2.6-for-ingo.orig/arch/x86/kernel/apic.c +++ linux-2.6-for-ingo/arch/x86/kernel/apic.c @@ -1833,6 +1833,11 @@ void __cpuinit generic_processor_info(in num_processors++; cpu = cpumask_next_zero(-1, cpu_present_mask); + if (version != apic_version[boot_cpu_physical_apicid]) + WARN_ONCE(1, + "ACPI: apic version mismatch, bootcpu: %x cpu %d: %x\n", + apic_version[boot_cpu_physical_apicid], cpu, version); + physid_set(apicid, phys_cpu_present_map); if (apicid == boot_cpu_physical_apicid) { /*
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