On Tue, Nov 21, 2023 at 04:26:04PM +0000, Alejandro Vallejo wrote: > Both Intel and AMD manuals agree that on x2APIC mode, the APIC LDR and ID > registers are derivable from each other through a fixed formula. > > Xen uses that formula, but applies it to vCPU IDs (which are sequential) > rather than x2APIC_IDs (which are not, at the moment). As I understand it, > this is an attempt to tightly pack vCPUs into clusters so each cluster has > 16 vCPUs rather than 8, but this is problematic for OSs that might read the > x2APIC_ID and internally derive LDR (or the other way around)
Ugh, forgot about Roger's commit message request >I would replace the underscore from x2APIC ID with a space instead. Happy for that to happen on commit if the rest looks ok. Cheers, Alejandro
