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authorVitaly Kuznetsov <vkuznets@redhat.com>2020-05-25 16:41:21 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2020-06-01 04:26:08 -0400
commit557a961abbe06ed9dfd3b55ef7bd6e68295cda3d (patch)
tree257d2ac75925f214eb581e5cf25baa2e0114575c /virt
parent2635b5c4a0e407b84f68e188c719f28ba0e9ae1b (diff)
KVM: x86: acknowledgment mechanism for async pf page ready notifications
If two page ready notifications happen back to back the second one is not delivered and the only mechanism we currently have is kvm_check_async_pf_completion() check in vcpu_run() loop. The check will only be performed with the next vmexit when it happens and in some cases it may take a while. With interrupt based page ready notification delivery the situation is even worse: unlike exceptions, interrupts are not handled immediately so we must check if the slot is empty. This is slow and unnecessary. Introduce dedicated MSR_KVM_ASYNC_PF_ACK MSR to communicate the fact that the slot is free and host should check its notification queue. Mandate using it for interrupt based 'page ready' APF event delivery. As kvm_check_async_pf_completion() is going away from vcpu_run() we need a way to communicate the fact that vcpu->async_pf.done queue has transitioned from empty to non-empty state. Introduce kvm_arch_async_page_present_queued() and KVM_REQ_APF_READY to do the job. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20200525144125.143875-7-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/async_pf.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
index 82e53f180a1a..f1e07fae84e9 100644
--- a/virt/kvm/async_pf.c
+++ b/virt/kvm/async_pf.c
@@ -51,6 +51,7 @@ static void async_pf_execute(struct work_struct *work)
unsigned long addr = apf->addr;
gpa_t cr2_or_gpa = apf->cr2_or_gpa;
int locked = 1;
+ bool first;
might_sleep();
@@ -69,10 +70,14 @@ static void async_pf_execute(struct work_struct *work)
kvm_arch_async_page_present(vcpu, apf);
spin_lock(&vcpu->async_pf.lock);
+ first = list_empty(&vcpu->async_pf.done);
list_add_tail(&apf->link, &vcpu->async_pf.done);
apf->vcpu = NULL;
spin_unlock(&vcpu->async_pf.lock);
+ if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
+ kvm_arch_async_page_present_queued(vcpu);
+
/*
* apf may be freed by kvm_check_async_pf_completion() after
* this point
@@ -201,6 +206,7 @@ retry_sync:
int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
{
struct kvm_async_pf *work;
+ bool first;
if (!list_empty_careful(&vcpu->async_pf.done))
return 0;
@@ -213,9 +219,13 @@ int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu)
INIT_LIST_HEAD(&work->queue); /* for list_del to work */
spin_lock(&vcpu->async_pf.lock);
+ first = list_empty(&vcpu->async_pf.done);
list_add_tail(&work->link, &vcpu->async_pf.done);
spin_unlock(&vcpu->async_pf.lock);
+ if (!IS_ENABLED(CONFIG_KVM_ASYNC_PF_SYNC) && first)
+ kvm_arch_async_page_present_queued(vcpu);
+
vcpu->async_pf.queued++;
return 0;
}

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