mirror of https://github.com/xemu-project/xemu.git
3401ea3cfe
The Power ISA has the concept of sub-processors: Hardware is allowed to sub-divide a multi-threaded processor into "sub-processors" that appear to privileged programs as multi-threaded processors with fewer threads. POWER9 and POWER10 have two modes, either every thread is a sub-processor or all threads appear as one multi-threaded processor. In the user manuals these are known as "LPAR per thread" / "Thread LPAR", and "LPAR per core" / "1 LPAR", respectively. The practical difference is: in thread LPAR mode, non-hypervisor SPRs are not shared between threads and msgsndp can not be used to message siblings. In 1 LPAR mode, some SPRs are shared and msgsndp is usable. Thrad LPAR allows multiple partitions to run concurrently on the same core, and is a requirement for KVM to run on POWER9/10 (which does not gang-schedule an LPAR on all threads of a core like POWER8 KVM). Traditionally, SMT in PAPR environments including PowerVM and the pseries QEMU machine with KVM acceleration behaves as in 1 LPAR mode. In OPAL systems, Thread LPAR is used. When adding SMT to the powernv machine, it is therefore preferable to emulate Thread LPAR. To account for this difference between pseries and powernv, an LPAR mode flag is added such that SPRs can be implemented as per-LPAR shared, and that becomes either per-thread or per-core depending on the flag. Reviewed-by: Joel Stanley <joel@jms.id.au> Reviewed-by: Cédric Le Goater <clg@kaod.org> Tested-by: Cédric Le Goater <clg@kaod.org> Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Message-ID: <20230705120631.27670-2-npiggin@gmail.com> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> |
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