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KVM: PPC: Book3S HV P9: Avoid cpu_in_guest atomics on entry and exit 

cpu_in_guest is set to determine if a CPU needs to be IPI'ed to exit
the guest and notice the need_tlb_flush bit.

This can be implemented as a global per-CPU pointer to the currently
running guest instead of per-guest cpumasks, saving 2 atomics per
entry/exit. P7/8 doesn't require cpu_in_guest, nor does a nested HV
(only the L0 does), so move it to the P9 HV path.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-50-npiggin@gmail.com
This commit is contained in:
Nicholas Piggin 2021-11-23 19:52:27 +10:00 committed by Michael Ellerman
parent 4c9a68914e
commit 434398ab5e
3 changed files with 22 additions and 19 deletions
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1
arch/powerpc/include/asm/kvm_book3s_64.h
View File

@ -44,7 +44,6 @@ struct kvm_nested_guest {
struct mutex tlb_lock; /* serialize page faults and tlbies */
struct kvm_nested_guest *next;
cpumask_t need_tlb_flush;
cpumask_t cpu_in_guest;
short prev_cpu[NR_CPUS];
u8 radix; /* is this nested guest radix */
};

1
arch/powerpc/include/asm/kvm_host.h
View File

@ -287,7 +287,6 @@ struct kvm_arch {
u32 online_vcores;
atomic_t hpte_mod_interest;
cpumask_t need_tlb_flush;
cpumask_t cpu_in_guest;
u8 radix;
u8 fwnmi_enabled;
u8 secure_guest;

39
arch/powerpc/kvm/book3s_hv.c
View File

@ -3009,19 +3009,18 @@ static void kvmppc_release_hwthread(int cpu)
tpaca->kvm_hstate.kvm_split_mode = NULL;
}
static DEFINE_PER_CPU(struct kvm *, cpu_in_guest);
static void radix_flush_cpu(struct kvm *kvm, int cpu, struct kvm_vcpu *vcpu)
{
struct kvm_nested_guest *nested = vcpu->arch.nested;
cpumask_t *cpu_in_guest, *need_tlb_flush;
cpumask_t *need_tlb_flush;
int i;
if (nested) {
if (nested)
need_tlb_flush = &nested->need_tlb_flush;
cpu_in_guest = &nested->cpu_in_guest;
} else {
else
need_tlb_flush = &kvm->arch.need_tlb_flush;
cpu_in_guest = &kvm->arch.cpu_in_guest;
}
cpu = cpu_first_tlb_thread_sibling(cpu);
for (i = cpu; i <= cpu_last_tlb_thread_sibling(cpu);
@ -3029,16 +3028,21 @@ static void radix_flush_cpu(struct kvm *kvm, int cpu, struct kvm_vcpu *vcpu)
cpumask_set_cpu(i, need_tlb_flush);
/*
* Make sure setting of bit in need_tlb_flush precedes
* testing of cpu_in_guest bits. The matching barrier on
* the other side is the first smp_mb() in kvmppc_run_core().
* Make sure setting of bit in need_tlb_flush precedes testing of
* cpu_in_guest. The matching barrier on the other side is hwsync
* when switching to guest MMU mode, which happens between
* cpu_in_guest being set to the guest kvm, and need_tlb_flush bit
* being tested.
*/
smp_mb();
for (i = cpu; i <= cpu_last_tlb_thread_sibling(cpu);
i += cpu_tlb_thread_sibling_step())
if (cpumask_test_cpu(i, cpu_in_guest))
i += cpu_tlb_thread_sibling_step()) {
struct kvm *running = *per_cpu_ptr(&cpu_in_guest, i);
if (running == kvm)
smp_call_function_single(i, do_nothing, NULL, 1);
}
}
static void do_migrate_away_vcpu(void *arg)
@ -3105,7 +3109,6 @@ static void kvmppc_start_thread(struct kvm_vcpu *vcpu, struct kvmppc_vcore *vc)
{
int cpu;
struct paca_struct *tpaca;
struct kvm *kvm = vc->kvm;
cpu = vc->pcpu;
if (vcpu) {
@ -3116,7 +3119,6 @@ static void kvmppc_start_thread(struct kvm_vcpu *vcpu, struct kvmppc_vcore *vc)
cpu += vcpu->arch.ptid;
vcpu->cpu = vc->pcpu;
vcpu->arch.thread_cpu = cpu;
cpumask_set_cpu(cpu, &kvm->arch.cpu_in_guest);
}
tpaca = paca_ptrs[cpu];
tpaca->kvm_hstate.kvm_vcpu = vcpu;
@ -3847,7 +3849,6 @@ static noinline void kvmppc_run_core(struct kvmppc_vcore *vc)
kvmppc_release_hwthread(pcpu + i);
if (sip && sip->napped[i])
kvmppc_ipi_thread(pcpu + i);
cpumask_clear_cpu(pcpu + i, &vc->kvm->arch.cpu_in_guest);
}
spin_unlock(&vc->lock);
@ -4015,8 +4016,14 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
}
} else {
struct kvm *kvm = vcpu->kvm;
kvmppc_xive_push_vcpu(vcpu);
__this_cpu_write(cpu_in_guest, kvm);
trap = kvmhv_vcpu_entry_p9(vcpu, time_limit, lpcr, tb);
__this_cpu_write(cpu_in_guest, NULL);
if (trap == BOOK3S_INTERRUPT_SYSCALL && !vcpu->arch.nested &&
!(vcpu->arch.shregs.msr & MSR_PR)) {
unsigned long req = kvmppc_get_gpr(vcpu, 3);
@ -4041,7 +4048,7 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit,
}
kvmppc_xive_pull_vcpu(vcpu);
if (kvm_is_radix(vcpu->kvm))
if (kvm_is_radix(kvm))
vcpu->arch.slb_max = 0;
}
@ -4531,8 +4538,6 @@ int kvmhv_run_single_vcpu(struct kvm_vcpu *vcpu, u64 time_limit,
powerpc_local_irq_pmu_restore(flags);
cpumask_clear_cpu(pcpu, &kvm->arch.cpu_in_guest);
preempt_enable();
/*