Re: [Xen-devel] APIC handling on x86-64

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>Testing is the scary thing for me. I have no access to Summit or ES7000 
>boxes, and I don't know what external testing is being done on those 
>systems and on what schedule. For all I know, bugs could be introduced 
>and not fixed for an arbitrary time. If I know there is testing 
>infrastructure I would like to move closer to x86/64's genapic code 
>(which uses generic mechanisms to determine what APIC mode to use) and 
>keep the minimal amount possible of default/bigsmp/summit/es7000 
>specific subarchitecture code. Still, some incremental progress on that 
>path is definitely achievable.

Whatever change we're going to do here, we'll have IBM test this on the
x460-s they reported the problem on. While we supposedly have at least
on x460 in our Lab, it's only a 16-(logical-)processor one, and there it
doesn't matter whether clustered logical or physical modes get used.

However, even if they disable HT on the 4-node system (reducing to 32
logical processors) they apparently also have a BIOS problem there in
that, with the intention to make the OS use clustered logical mode, they
assign processors to 16 clusters (2 processors each), ending up with
two processors with APIC IDs of the form 0xFx, which to my
understanding is valid only for physical mode.

Jan

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