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ppc/pnv: Add an LPAR per core machine option

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Recent POWER CPUs can operate in "LPAR per core" or "LPAR per thread"
modes. In per-core mode, some SPRs and IPI doorbells are shared between
threads in a core. In per-thread mode, supervisor and user state is
not shared between threads.

OpenPOWER systems after POWER8 use LPAR per thread mode, and it is
required for KVM. Enterprise systems use LPAR per core mode, as they
partition the machine by core.

Implement a lpar-per-core machine option for powernv machines. This
is fixed true for POWER8 machines, and defaults off for P9 and P10.

With this change, powernv8 SMT now works sufficiently to run Linux,
with a single socket. Multi-threaded KVM guests still have problems,
as does multi-socket Linux boot.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
This commit is contained in:
Nicholas Piggin 2024-05-24 15:02:46 +10:00
parent c889195508
commit 3b5ea01e98
6 changed files with 52 additions and 1 deletions
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3
target/ppc/cpu_init.c
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@ -6786,7 +6786,8 @@ void cpu_ppc_set_1lpar(PowerPCCPU *cpu)
/*
* pseries SMT means "LPAR per core" mode, e.g., msgsndp is usable
* between threads.
* between threads. powernv be in either mode, and it mostly affects
* supervisor visible registers and instructions.
*/
if (env->flags & POWERPC_FLAG_SMT) {
env->flags |= POWERPC_FLAG_SMT_1LPAR;