Messages in this thread | | | Date | Mon, 19 Jan 2009 09:08:31 -0800 | From | Mike Travis <> | Subject | Re: [PATCH] x86: put trigger in to detect mismatched apic versions. |
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Jack Steiner wrote: > On Sun, Jan 18, 2009 at 08:08:49PM +0100, Ingo Molnar wrote: >> * Jack Steiner <steiner@sgi.com> wrote: >> >>>> 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 >>> Not strictly true. The apicids in the ACPI tables are always globally >>> unique across the entire system. Because of the size of UV systems, UV >>> needs 16 bit apicids. This fits in the ACPI apicid id/eid fields.
Ahh, I did mean to say this applied to the lower 8 bits only. >>> >>> The actual processor apicid register is unfortunately only 11 bits and >>> there are some restrictions on the actual values loaded into the apicid >>> register.
This is for x2apics only, yes?
>>> >>> If we can put unique ids into the apicid register, we do. If we can't, >>> the function that reads the apicid will automatically supply the rest of >>> the bits. Most of the kernel is unaware that the processor apicid >>> register may have only a subset of the bits that are in the ACPI tables.
>> apicid remapping is something we need/want, so we cannot remove that >> array. But it would be nice to offload such properties to the percpu area >> instead - is there any reason why that is hard? The local apic is attached >> to a CPU in any case. Is there some early init reason that complicates >> this? > > I can't think of any reason why it could not be moved into > the percpu data area. Mike???
WHich array? There are two now, the x86_cpu_to_apicid and x86_bios_cpu_apicid that are in the percpu area? (Maybe it's time to find out why there are two. ;-)
Thanks, Mike
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