[PATCH v2 1/5] KVM: x86: Introduce KVM_REQ_RING_SOFT_FULL

[Gavin Shan]

This adds KVM_REQ_RING_SOFT_FULL, which is raised when the dirty
ring of the specific VCPU becomes softly full in kvm_dirty_ring_push().
The VCPU is enforced to exit when the request is raised and its
dirty ring is softly full on its entrance.

Suggested-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
 arch/x86/kvm/x86.c       | 5 +++--
 include/linux/kvm_host.h | 1 +
 virt/kvm/dirty_ring.c    | 4 ++++
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 43a6a7efc6ec..7f368f59f033 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10265,8 +10265,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 	bool req_immediate_exit = false;
 
 	/* Forbid vmenter if vcpu dirty ring is soft-full */
-	if (unlikely(vcpu->kvm->dirty_ring_size &&
-		     kvm_dirty_ring_soft_full(&vcpu->dirty_ring))) {
+	if (kvm_check_request(KVM_REQ_RING_SOFT_FULL, vcpu) &&
+	    kvm_dirty_ring_soft_full(&vcpu->dirty_ring)) {
+		kvm_make_request(KVM_REQ_RING_SOFT_FULL, vcpu);
 		vcpu->run->exit_reason = KVM_EXIT_DIRTY_RING_FULL;
 		trace_kvm_dirty_ring_exit(vcpu);
 		r = 0;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f4519d3689e1..53fa3134fee0 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -157,6 +157,7 @@ static inline bool is_error_page(struct page *page)
 #define KVM_REQ_VM_DEAD           (1 | KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
 #define KVM_REQ_UNBLOCK           2
 #define KVM_REQ_UNHALT            3
+#define KVM_REQ_RING_SOFT_FULL    4
 #define KVM_REQUEST_ARCH_BASE     8
 
 /*
diff --git a/virt/kvm/dirty_ring.c b/virt/kvm/dirty_ring.c
index f4c2a6eb1666..f0e49937bc9e 100644
--- a/virt/kvm/dirty_ring.c
+++ b/virt/kvm/dirty_ring.c
@@ -149,6 +149,7 @@ int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_dirty_ring *ring)
 
 void kvm_dirty_ring_push(struct kvm_dirty_ring *ring, u32 slot, u64 offset)
 {
+	struct kvm_vcpu *vcpu = container_of(ring, struct kvm_vcpu, dirty_ring);
 	struct kvm_dirty_gfn *entry;
 
 	/* It should never get full */
@@ -166,6 +167,9 @@ void kvm_dirty_ring_push(struct kvm_dirty_ring *ring, u32 slot, u64 offset)
 	kvm_dirty_gfn_set_dirtied(entry);
 	ring->dirty_index++;
 	trace_kvm_dirty_ring_push(ring, slot, offset);
+
+	if (kvm_dirty_ring_soft_full(ring))
+		kvm_make_request(KVM_REQ_RING_SOFT_FULL, vcpu);
 }
 
 struct page *kvm_dirty_ring_get_page(struct kvm_dirty_ring *ring, u32 offset)
-- 
2.23.0