* [PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches
@ 2021-08-12 14:09 Eugenio Pérez
2021-08-16 2:51 ` Jason Wang
0 siblings, 1 reply; 4+ messages in thread
From: Eugenio Pérez @ 2021-08-12 14:09 UTC (permalink / raw)
To: qemu-devel; +Cc: Eli Cohen, Jason Wang, Cindy Lu, Michael S. Tsirkin
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
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches
2021-08-12 14:09 [PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches Eugenio Pérez
@ 2021-08-16 2:51 ` Jason Wang
2021-08-16 5:36 ` Michael S. Tsirkin
0 siblings, 1 reply; 4+ messages in thread
From: Jason Wang @ 2021-08-16 2:51 UTC (permalink / raw)
To: Eugenio Pérez; +Cc: Eli Cohen, qemu-devel, Cindy Lu, Michael S. Tsirkin
On Thu, Aug 12, 2021 at 10:09 PM Eugenio Pérez <eperezma@redhat.com> wrote:
>
> 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.
Acked-by: Jason Wang <jasowang@redhat.com>
>
> 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
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches
2021-08-16 2:51 ` Jason Wang
@ 2021-08-16 5:36 ` Michael S. Tsirkin
2021-08-16 6:00 ` Jason Wang
0 siblings, 1 reply; 4+ messages in thread
From: Michael S. Tsirkin @ 2021-08-16 5:36 UTC (permalink / raw)
To: Jason Wang; +Cc: Eugenio Pérez, Eli Cohen, qemu-devel, Cindy Lu
On Mon, Aug 16, 2021 at 10:51:57AM +0800, Jason Wang wrote:
> On Thu, Aug 12, 2021 at 10:09 PM Eugenio Pérez <eperezma@redhat.com> wrote:
> >
> > 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.
>
> Acked-by: Jason Wang <jasowang@redhat.com>
Oops. You missed by pull request by a hairwidth.
> >
> > 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
> >
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches
2021-08-16 5:36 ` Michael S. Tsirkin
@ 2021-08-16 6:00 ` Jason Wang
0 siblings, 0 replies; 4+ messages in thread
From: Jason Wang @ 2021-08-16 6:00 UTC (permalink / raw)
To: Michael S. Tsirkin; +Cc: Eugenio Pérez, Eli Cohen, qemu-devel, Cindy Lu
在 2021/8/16 下午1:36, Michael S. Tsirkin 写道:
> On Mon, Aug 16, 2021 at 10:51:57AM +0800, Jason Wang wrote:
>> On Thu, Aug 12, 2021 at 10:09 PM Eugenio Pérez<eperezma@redhat.com> wrote:
>>> 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.
>> Acked-by: Jason Wang<jasowang@redhat.com>
> Oops. You missed by pull request by a hairwidth.
It's fine.
Thanks
^ permalink raw reply [flat|nested] 4+ messages in thread
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2021-08-12 14:09 [PATCH v3] vhost-vdpa: Do not send empty IOTLB update batches Eugenio Pérez
2021-08-16 2:51 ` Jason Wang
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