diff mbox series

[v3,4/4] kvm: Enable dirty ring for arm64

Message ID 20230509022122.20888-5-gshan@redhat.com
State New
Headers show
Series hw/arm/virt: Support dirty ring | expand

Commit Message

Gavin Shan May 9, 2023, 2:21 a.m. UTC 
arm64 has different capability from x86 to enable the dirty ring, which
is KVM_CAP_DIRTY_LOG_RING_ACQ_REL. Besides, arm64 also needs the backup
bitmap extension (KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP) when 'kvm-arm-gicv3'
or 'arm-its-kvm' device is enabled. Here the extension is always enabled
and the unnecessary overhead to do the last stage of dirty log synchronization
when those two devices aren't used is introduced, but the overhead should
be very small and acceptable. The benefit is cover future cases where those
two devices are used without modifying the code.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>
---
 accel/kvm/kvm-all.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

Comments

Peter Xu May 9, 2023, 1:54 p.m. UTC | #1 
On Tue, May 09, 2023 at 12:21:22PM +1000, Gavin Shan wrote:
> arm64 has different capability from x86 to enable the dirty ring, which
> is KVM_CAP_DIRTY_LOG_RING_ACQ_REL. Besides, arm64 also needs the backup
> bitmap extension (KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP) when 'kvm-arm-gicv3'
> or 'arm-its-kvm' device is enabled. Here the extension is always enabled
> and the unnecessary overhead to do the last stage of dirty log synchronization
> when those two devices aren't used is introduced, but the overhead should
> be very small and acceptable. The benefit is cover future cases where those
> two devices are used without modifying the code.
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> Reviewed-by: Juan Quintela <quintela@redhat.com>
> Tested-by: Zhenyu Zhang <zhenyzha@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>
diff mbox series

Patch

diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 5d0de9d0a8..7679f397ae 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -1466,6 +1466,7 @@  static int kvm_dirty_ring_init(KVMState *s)
 {
     uint32_t ring_size = s->kvm_dirty_ring_size;
     uint64_t ring_bytes = ring_size * sizeof(struct kvm_dirty_gfn);
+    unsigned int capability = KVM_CAP_DIRTY_LOG_RING;
     int ret;
 
     s->kvm_dirty_ring_size = 0;
@@ -1480,7 +1481,12 @@  static int kvm_dirty_ring_init(KVMState *s)
      * Read the max supported pages. Fall back to dirty logging mode
      * if the dirty ring isn't supported.
      */
-    ret = kvm_vm_check_extension(s, KVM_CAP_DIRTY_LOG_RING);
+    ret = kvm_vm_check_extension(s, capability);
+    if (ret <= 0) {
+        capability = KVM_CAP_DIRTY_LOG_RING_ACQ_REL;
+        ret = kvm_vm_check_extension(s, capability);
+    }
+
     if (ret <= 0) {
         warn_report("KVM dirty ring not available, using bitmap method");
         return 0;
@@ -1493,13 +1499,26 @@  static int kvm_dirty_ring_init(KVMState *s)
         return -EINVAL;
     }
 
-    ret = kvm_vm_enable_cap(s, KVM_CAP_DIRTY_LOG_RING, 0, ring_bytes);
+    ret = kvm_vm_enable_cap(s, capability, 0, ring_bytes);
     if (ret) {
         error_report("Enabling of KVM dirty ring failed: %s. "
                      "Suggested minimum value is 1024.", strerror(-ret));
         return -EIO;
     }
 
+    /* Enable the backup bitmap if it is supported */
+    ret = kvm_vm_check_extension(s, KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP);
+    if (ret > 0) {
+        ret = kvm_vm_enable_cap(s, KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP, 0);
+        if (ret) {
+            error_report("Enabling of KVM dirty ring's backup bitmap failed: "
+                         "%s. ", strerror(-ret));
+            return -EIO;
+        }
+
+        s->kvm_dirty_ring_with_bitmap = true;
+    }
+
     s->kvm_dirty_ring_size = ring_size;
     s->kvm_dirty_ring_bytes = ring_bytes;