Messages in this thread | ![/](/images/icornerl.gif) | | Date | Fri, 04 Jul 2003 09:18:12 -0700 | From | "Martin J. Bligh" <> | Subject | Re: 2.5.74-mm1 fails to boot due to APIC trouble, 2.5.73mm3 works. |
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> On Fri, 4 Jul 2003, Martin J. Bligh wrote: > >> Is it really necessary to turn half the apic code upside down in order >> to fix this? What's the actual bugfix that's buried in this cleanup? > > The way i see it is that you can't use NR_CPUS to determine the upper > bound on APIC IDs. e.g. my 3way is normally configured with NR_CPUS = 3 > but has APIC IDs of 0, 3 and 4. We need to make a distinction.
Fair enough. But that would seem to be a simpler operation than this patch.
>> > - if (i >= 0xf) >> > + if (i >= APIC_BROADCAST_ID) >> >> Is that always correct? it's not equivalent. > > Well we really want APIC_MAX_ID (or whatever it's called)
Indeed. maybe MAX_PHYS_APIC_ID or something (it's different for logical). We break it out in subarch, but it's the same everywhere, which seems utterly useless - is probably historical cruft that needs to die. But that sounds like a separate issue, and a separate patch to me.
>> > - for (bit = 0; kicked < NR_CPUS && bit < 8*sizeof(cpumask_t); bit++) { >> > + for (bit = 0; kicked < NR_CPUS && bit < MAX_APICS; bit++) { >> >> Is that the actual one-line bugfix this is all about? > > No, the problem is no space for physical ids in cpumask bitmaps, this > could manifest itself later on unless we fix it now.
Ugh, are you saying the cpumask stuff shrinks masks to < 32 bits if NR_CPUS is low enough? If so, I can see more point to the patch, but it still seems like violent overkill. Stopping it doing that would probably fix it ... I can't imagine it buys you much.
phys_cpu_present_map started off as an unsigned long, and I reused it in a fairly twisted way for NUMA-Q. As it's an array that's bounded by apic space, using the bios_cpu_apicid method that summit uses would be a much cleaner fix, and just leave the old one as a long bitmask like it used to be - which is fine for non- clustered apic systems, and saves inventing a whole new data type. See the cpu_present_to_apicid abstraction.
>> Hmmmm. What are you using physical apicids here for? They seem >> irrelevant to this function. > > Urgh, it's really hard to determine what these functions really want half > the time. But that change does look wrong.
Yeah, things taking logical apicids, and turning them into cpu numbers presumably shouldn't have to touch that.
M.
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