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[PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches
From: |
Eugenio Pérez |
Subject: |
[PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches |
Date: |
Thu, 12 Aug 2021 16:09:33 +0200 |
With the introduction of the batch hinting, meaningless batches can be
created with no IOTLB updates if the memory region was skipped by
vhost_vdpa_listener_skipped_section. This is the case of host notifiers
memory regions, device un/realize, and others. This causes the vdpa
device to receive dma mapping settings with no changes, a possibly
expensive operation for nothing.
To avoid that, VHOST_IOTLB_BATCH_BEGIN hint is delayed until we have a
meaningful (not skipped section) mapping or unmapping operation, and
VHOST_IOTLB_BATCH_END is not written unless at least one of _UPDATE /
_INVALIDATE has been issued.
v3:
* Use a bool instead of a counter avoiding potential number wrapping
* Fix bad check on _commit
* Move VHOST_BACKEND_F_IOTLB_BATCH check to
vhost_vdpa_iotlb_batch_begin_once
v2 (from RFC):
* Rename misleading name
* Abstract start batching function for listener_add/del
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
include/hw/virtio/vhost-vdpa.h | 1 +
hw/virtio/vhost-vdpa.c | 35 ++++++++++++++++++++++------------
2 files changed, 24 insertions(+), 12 deletions(-)
diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index e98e327f12..6b9288fef8 100644
--- a/include/hw/virtio/vhost-vdpa.h
+++ b/include/hw/virtio/vhost-vdpa.h
@@ -23,6 +23,7 @@ typedef struct vhost_vdpa {
int device_fd;
int index;
uint32_t msg_type;
+ bool iotlb_batch_begin_sent;
MemoryListener listener;
struct vhost_dev *dev;
VhostVDPAHostNotifier notifier[VIRTIO_QUEUE_MAX];
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 6ce94a1f4d..93b7db61d1 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -89,19 +89,13 @@ static int vhost_vdpa_dma_unmap(struct vhost_vdpa *v,
hwaddr iova,
return ret;
}
-static void vhost_vdpa_listener_begin(MemoryListener *listener)
+static void vhost_vdpa_listener_begin_batch(struct vhost_vdpa *v)
{
- struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
- struct vhost_dev *dev = v->dev;
- struct vhost_msg_v2 msg = {};
int fd = v->device_fd;
-
- if (!(dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH))) {
- return;
- }
-
- msg.type = v->msg_type;
- msg.iotlb.type = VHOST_IOTLB_BATCH_BEGIN;
+ struct vhost_msg_v2 msg = {
+ .type = v->msg_type,
+ .iotlb.type = VHOST_IOTLB_BATCH_BEGIN,
+ };
if (write(fd, &msg, sizeof(msg)) != sizeof(msg)) {
error_report("failed to write, fd=%d, errno=%d (%s)",
@@ -109,6 +103,16 @@ static void vhost_vdpa_listener_begin(MemoryListener
*listener)
}
}
+static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v)
+{
+ if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH) &&
+ !v->iotlb_batch_begin_sent) {
+ vhost_vdpa_listener_begin_batch(v);
+ }
+
+ v->iotlb_batch_begin_sent = true;
+}
+
static void vhost_vdpa_listener_commit(MemoryListener *listener)
{
struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
@@ -120,6 +124,10 @@ static void vhost_vdpa_listener_commit(MemoryListener
*listener)
return;
}
+ if (!v->iotlb_batch_begin_sent) {
+ return;
+ }
+
msg.type = v->msg_type;
msg.iotlb.type = VHOST_IOTLB_BATCH_END;
@@ -127,6 +135,8 @@ static void vhost_vdpa_listener_commit(MemoryListener
*listener)
error_report("failed to write, fd=%d, errno=%d (%s)",
fd, errno, strerror(errno));
}
+
+ v->iotlb_batch_begin_sent = false;
}
static void vhost_vdpa_listener_region_add(MemoryListener *listener,
@@ -170,6 +180,7 @@ static void vhost_vdpa_listener_region_add(MemoryListener
*listener,
llsize = int128_sub(llend, int128_make64(iova));
+ vhost_vdpa_iotlb_batch_begin_once(v);
ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
vaddr, section->readonly);
if (ret) {
@@ -221,6 +232,7 @@ static void vhost_vdpa_listener_region_del(MemoryListener
*listener,
llsize = int128_sub(llend, int128_make64(iova));
+ vhost_vdpa_iotlb_batch_begin_once(v);
ret = vhost_vdpa_dma_unmap(v, iova, int128_get64(llsize));
if (ret) {
error_report("vhost_vdpa dma unmap error!");
@@ -234,7 +246,6 @@ static void vhost_vdpa_listener_region_del(MemoryListener
*listener,
* depends on the addnop().
*/
static const MemoryListener vhost_vdpa_memory_listener = {
- .begin = vhost_vdpa_listener_begin,
.commit = vhost_vdpa_listener_commit,
.region_add = vhost_vdpa_listener_region_add,
.region_del = vhost_vdpa_listener_region_del,
--
2.27.0
- [PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches,
Eugenio Pérez <=