diff options
| author | Nicholas Piggin <npiggin@gmail.com> | 2021-11-23 19:51:48 +1000 |
|---|---|---|
| committer | Michael Ellerman <mpe@ellerman.id.au> | 2021-11-24 21:08:57 +1100 |
| commit | d3c8a2d3740d93778ea102d4c781746d284177bf (patch) | |
| tree | acbdd215e8cc9bb051be35e5812584b25d55e0dc /arch/powerpc/kvm/book3s_hv.c | |
| parent | 46f9caf1a246a5c0622fa8cc7e673658e925f97e (diff) | |
KVM: PPC: Book3S HV: Don't always save PMU for guest capable of nesting
Provide a config option that controls the workaround added by commit
63279eeb7f93 ("KVM: PPC: Book3S HV: Always save guest pmu for guest
capable of nesting"). The option defaults to y for now, but is expected
to go away within a few releases.
Nested capable guests running with the earlier commit 178266389794
("KVM: PPC: Book3S HV Nested: Reflect guest PMU in-use to L0 when guest
SPRs are live") will now indicate the PMU in-use status of their guests,
which means the parent does not need to unconditionally save the PMU for
nested capable guests.
After this latest round of performance optimisations, this option costs
about 540 cycles or 10% entry/exit performance on a POWER9 nested-capable
guest.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
References: 178266389794 ("KVM: PPC: Book3S HV Nested: Reflect guest PMU in-use to L0 when guest SPRs are live")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-11-npiggin@gmail.com
Diffstat (limited to 'arch/powerpc/kvm/book3s_hv.c')
| -rw-r--r-- | arch/powerpc/kvm/book3s_hv.c | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index a683ee5f420a..6e760f48bbaf 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -4047,8 +4047,14 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, vcpu->arch.vpa.dirty = 1; save_pmu = lp->pmcregs_in_use; } - /* Must save pmu if this guest is capable of running nested guests */ - save_pmu |= nesting_enabled(vcpu->kvm); + if (IS_ENABLED(CONFIG_KVM_BOOK3S_HV_NESTED_PMU_WORKAROUND)) { + /* + * Save pmu if this guest is capable of running nested guests. + * This is option is for old L1s that do not set their + * lppaca->pmcregs_in_use properly when entering their L2. + */ + save_pmu |= nesting_enabled(vcpu->kvm); + } kvmhv_save_guest_pmu(vcpu, save_pmu); #ifdef CONFIG_PPC_PSERIES |