Moving the mtmsrd after the host SPRs are saved and before the guest
SPRs start to be loaded can prevent an SPR scoreboard stall (because
the mtmsrd is L=1 type which does not cause context synchronisation.
This is also now more convenient to combined with the mtmsrd L=0
instruction to enable facilities just below, but that is not done yet.
-12 cycles (7791) POWER9 virt-mode NULL hcall
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
---
arch/powerpc/kvm/book3s_hv.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 3ac5dbdb59f8..b8b0695a9312 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -4015,6 +4015,18 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
save_p9_host_os_sprs(&host_os_sprs);
+ /*
+ * This could be combined with MSR[RI] clearing, but that expands
+ * the unrecoverable window. It would be better to cover unrecoverable
+ * with KVM bad interrupt handling rather than use MSR[RI] at all.
+ *
+ * Much more difficult and less worthwhile to combine with IR/DR
+ * disable.
+ */
+ hard_irq_disable();
+ if (lazy_irq_pending())
+ return 0;
+
/* MSR bits may have been cleared by context switch */
msr = 0;
if (IS_ENABLED(CONFIG_PPC_FPU))
@@ -4512,6 +4524,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
struct kvmppc_vcore *vc;
struct kvm *kvm = vcpu->kvm;
struct kvm_nested_guest *nested = vcpu->arch.nested;
+ unsigned long flags;
trace_kvmppc_run_vcpu_enter(vcpu);
@@ -4555,11 +4568,11 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
if (kvm_is_radix(kvm))
kvmppc_prepare_radix_vcpu(vcpu, pcpu);
- local_irq_disable();
- hard_irq_disable();
+ /* flags save not required, but irq_pmu has no disable/enable API */
+ powerpc_local_irq_pmu_save(flags);
if (signal_pending(current))
goto sigpend;
- if (lazy_irq_pending() || need_resched() || !kvm->arch.mmu_ready)
+ if (need_resched() || !kvm->arch.mmu_ready)
goto out;
if (!nested) {
@@ -4614,7 +4627,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
guest_exit_irqoff();
- local_irq_enable();
+ powerpc_local_irq_pmu_restore(flags);
cpumask_clear_cpu(pcpu, &kvm->arch.cpu_in_guest);
@@ -4672,7 +4685,7 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
run->exit_reason = KVM_EXIT_INTR;
vcpu->arch.ret = -EINTR;
out:
- local_irq_enable();
+ powerpc_local_irq_pmu_restore(flags);
preempt_enable();
goto done;
}
--
2.23.0
