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SubjectRe: [PATCH][2.4] generic cluster APIC support for systems with more than 8 CPUs
On Wed, Dec 18, 2002 at 02:36:20PM -0800, Pallipadi, Venkatesh wrote:
> These reasons together led to panics on other OEM systems with > 8 CPUS. The
> patch tries to fix this issue in a generic way (in place of having multiple
> hacks for different OEMs). Note, the patch only intends to change the
> initialization of systems with more than 8 CPUs and it will not affect
> other systems (apart from possible bugs in my code itself).

Any pointers to these systems?

> - Separate out xAPIC stuff from APIC destination setup. And the availability of
> xAPIC support can actually be determined from the LAPIC version.

Are you sure? IIRC some of the early summit boxens didn't report the
right versions..

> - physical mode support _removed_, as we can use clustered logical setup to
> support can support upto a max of 60 CPUs. This is mainly because of the
> advantage of being able to setup IOAPICs in LowestPrio, when using clustered mode.

does this really not break anything in the fragile summit setups?

- bool 'Multi-node NUMA system support' CONFIG_X86_NUMA
- if [ "$CONFIG_X86_NUMA" = "y" ]; then
+ bool 'Clustered APIC (> 8 CPUs) support' CONFIG_X86_APIC_CLUSTER
+ if [ "$CONFIG_X86_APIC_CLUSTER" = "y" ]; then
+ define_bool CONFIG_X86_CLUSTERED_APIC y


unsigned long id;
- if(clustered_apic_mode == CLUSTERED_APIC_XAPIC)
- id = physical_to_logical_apicid(hard_smp_processor_id());
+ if(clustered_apic_mode)
+ id = cpu_2_logical_apicid[smp_processor_id()];

Okay, this was wrong before, but any chance you could use proper
style here (i.e. if ()

id = 1UL << smp_processor_id();

- if (mp_ioapics[apic].mpc_apicid >= apic_broadcast_id) {
+ if ( !xapic_support &&
+ (mp_ioapics[apic].mpc_apicid >= apic_broadcast_id)) {

if (!xapic_support &&
(mp_ioapics[apic].mpc_apicid >= apic_broadcast_id)) {

+ if ( !xapic_support ) {


- if (clustered_apic_mode == CLUSTERED_APIC_NUMAQ) {
+ if (clustered_apic_mode &&
+ (configured_platform_type == CONFIGURED_PLATFORM_NUMA) ) {

Doesn;t configured_platform_type == CONFIGURED_PLATFORM_NUMA imply
clustered_apic_mode? and it should be at least CONFIGURED_PLATFORM_NUMAQ,
btw. Probably better something short like SUBARCH_NUMAQ..

Except of that the patch looks fine, but IMHO something like that should
get testing in 2.5 first.
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