Iterating over set bits in 'vcpu_bitmap' should be faster than going
through all vCPUs, especially when just a few bits are set.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
virt/kvm/kvm_main.c | 83 ++++++++++++++++++++++++++-------------------
1 file changed, 49 insertions(+), 34 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2082aceffbf6..5d2b1f0fafaf 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -261,49 +261,64 @@ static inline bool kvm_kick_many_cpus(cpumask_var_t tmp, bool wait)
return true;
}
+static void kvm_make_vcpu_request(struct kvm *kvm, struct kvm_vcpu *vcpu,
+ unsigned int req, cpumask_var_t tmp,
+ int current_cpu)
+{
+ int cpu = vcpu->cpu;
+
+ kvm_make_request(req, vcpu);
+
+ if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu))
+ return;
+
+ /*
+ * tmp can be "unavailable" if cpumasks are allocated off stack as
+ * allocation of the mask is deliberately not fatal and is handled by
+ * falling back to kicking all online CPUs.
+ */
+ if (!cpumask_available(tmp))
+ return;
+
+ /*
+ * Note, the vCPU could get migrated to a different pCPU at any point
+ * after kvm_request_needs_ipi(), which could result in sending an IPI
+ * to the previous pCPU. But, that's OK because the purpose of the IPI
+ * is to ensure the vCPU returns to OUTSIDE_GUEST_MODE, which is
+ * satisfied if the vCPU migrates. Entering READING_SHADOW_PAGE_TABLES
+ * after this point is also OK, as the requirement is only that KVM wait
+ * for vCPUs that were reading SPTEs _before_ any changes were
+ * finalized. See kvm_vcpu_kick() for more details on handling requests.
+ */
+ if (kvm_request_needs_ipi(vcpu, req)) {
+ cpu = READ_ONCE(vcpu->cpu);
+ if (cpu != -1 && cpu != current_cpu)
+ __cpumask_set_cpu(cpu, tmp);
+ }
+}
+
bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req,
struct kvm_vcpu *except,
unsigned long *vcpu_bitmap, cpumask_var_t tmp)
{
- int i, cpu, me;
+ int i, me;
struct kvm_vcpu *vcpu;
bool called;
me = get_cpu();
- kvm_for_each_vcpu(i, vcpu, kvm) {
- if ((vcpu_bitmap && !test_bit(i, vcpu_bitmap)) ||
- vcpu == except)
- continue;
-
- kvm_make_request(req, vcpu);
-
- if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu))
- continue;
-
- /*
- * tmp can be "unavailable" if cpumasks are allocated off stack
- * as allocation of the mask is deliberately not fatal and is
- * handled by falling back to kicking all online CPUs.
- */
- if (!cpumask_available(tmp))
- continue;
-
- /*
- * Note, the vCPU could get migrated to a different pCPU at any
- * point after kvm_request_needs_ipi(), which could result in
- * sending an IPI to the previous pCPU. But, that's ok because
- * the purpose of the IPI is to ensure the vCPU returns to
- * OUTSIDE_GUEST_MODE, which is satisfied if the vCPU migrates.
- * Entering READING_SHADOW_PAGE_TABLES after this point is also
- * ok, as the requirement is only that KVM wait for vCPUs that
- * were reading SPTEs _before_ any changes were finalized. See
- * kvm_vcpu_kick() for more details on handling requests.
- */
- if (kvm_request_needs_ipi(vcpu, req)) {
- cpu = READ_ONCE(vcpu->cpu);
- if (cpu != -1 && cpu != me)
- __cpumask_set_cpu(cpu, tmp);
+ if (vcpu_bitmap) {
+ for_each_set_bit(i, vcpu_bitmap, KVM_MAX_VCPUS) {
+ vcpu = kvm_get_vcpu(kvm, i);
+ if (!vcpu || vcpu == except)
+ continue;
+ kvm_make_vcpu_request(kvm, vcpu, req, tmp, me);
+ }
+ } else {
+ kvm_for_each_vcpu(i, vcpu, kvm) {
+ if (vcpu == except)
+ continue;
+ kvm_make_vcpu_request(kvm, vcpu, req, tmp, me);
}
}
--
2.31.1
