KVM: Add dirty-ring-size property

Add a parameter for dirty gfn count for dirty rings.  If zero, dirty ring is
disabled.  Otherwise dirty ring will be enabled with the per-vcpu gfn count as
specified.  If dirty ring cannot be enabled due to unsupported kernel or
illegal parameter, it'll fallback to dirty logging.

By default, dirty ring is not enabled (dirty-gfn-count default to 0).

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210506160549.130416-9-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 46 insertions, 0 deletions

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index df9fbf59a6..5afe15ae66 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -126,6 +126,8 @@ struct KVMState
         KVMMemoryListener *ml;
         AddressSpace *as;
     } *as;
+    uint64_t kvm_dirty_ring_bytes;  /* Size of the per-vcpu dirty ring */
+    uint32_t kvm_dirty_ring_size;   /* Number of dirty GFNs per ring */
 };
 
 KVMState *kvm_state;
@@ -3182,6 +3184,42 @@ bool kvm_kernel_irqchip_split(void)
     return kvm_state->kernel_irqchip_split == ON_OFF_AUTO_ON;
 }
 
+static void kvm_get_dirty_ring_size(Object *obj, Visitor *v,
+                                    const char *name, void *opaque,
+                                    Error **errp)
+{
+    KVMState *s = KVM_STATE(obj);
+    uint32_t value = s->kvm_dirty_ring_size;
+
+    visit_type_uint32(v, name, &value, errp);
+}
+
+static void kvm_set_dirty_ring_size(Object *obj, Visitor *v,
+                                    const char *name, void *opaque,
+                                    Error **errp)
+{
+    KVMState *s = KVM_STATE(obj);
+    Error *error = NULL;
+    uint32_t value;
+
+    if (s->fd != -1) {
+        error_setg(errp, "Cannot set properties after the accelerator has been initialized");
+        return;
+    }
+
+    visit_type_uint32(v, name, &value, &error);
+    if (error) {
+        error_propagate(errp, error);
+        return;
+    }
+    if (value & (value - 1)) {
+        error_setg(errp, "dirty-ring-size must be a power of two.");
+        return;
+    }
+
+    s->kvm_dirty_ring_size = value;
+}
+
 static void kvm_accel_instance_init(Object *obj)
 {
     KVMState *s = KVM_STATE(obj);
@@ -3191,6 +3229,8 @@ static void kvm_accel_instance_init(Object *obj)
     s->kvm_shadow_mem = -1;
     s->kernel_irqchip_allowed = true;
     s->kernel_irqchip_split = ON_OFF_AUTO_AUTO;
+    /* KVM dirty ring is by default off */
+    s->kvm_dirty_ring_size = 0;
 }
 
 static void kvm_accel_class_init(ObjectClass *oc, void *data)
@@ -3212,6 +3252,12 @@ static void kvm_accel_class_init(ObjectClass *oc, void *data)
         NULL, NULL);
     object_class_property_set_description(oc, "kvm-shadow-mem",
         "KVM shadow MMU size");
+
+    object_class_property_add(oc, "dirty-ring-size", "uint32",
+        kvm_get_dirty_ring_size, kvm_set_dirty_ring_size,
+        NULL, NULL);
+    object_class_property_set_description(oc, "dirty-ring-size",
+        "Size of KVM dirty page ring buffer (default: 0, i.e. use bitmap)");
 }
 
 static const TypeInfo kvm_accel_type = {