On Wed, 2023-03-29 at 22:30 +0700, Bui Quang Minh wrote: > > > > > I do some more testing on my hardware, your point is correct when dest > > == 0xffffffff, the interrupt is delivered to all APICs regardless of > > their mode. > > To be precisely, it only broadcasts to CPUs in xAPIC mode if the IPI > destination mode is physical. In case the destination mode is logical, > flat model/cluster model rule applies to determine if the xAPIC CPUs > accept the IPI. Wow, this is so complicated :)
So even if you send to *all* of the first 8 CPUs in a cluster (e.g. cluster 0x0001 giving a destination 0x000100FF, a CPU in xAPIC mode doesn't see that as a broadcast because it's logical mode? I would have assumed that a CPU in xAPIC mode would have looked at the low byte and interpreted it as xAPIC logical mode, with the cluster in the high nybble and the 4-bit mask in the low nybble?
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