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[PATCH v2] vhost-vdpa: Do not send empty IOTLB update batches

Eugenio Pérez posted 1 patch 2 years, 8 months ago
Failed in applying to current master (apply log)
There is a newer version of this series
include/hw/virtio/vhost-vdpa.h |  1 +
hw/virtio/vhost-vdpa.c         | 50 ++++++++++++++++++++++++++--------
2 files changed, 39 insertions(+), 12 deletions(-)
[PATCH v2] vhost-vdpa: Do not send empty IOTLB update batches
Posted by Eugenio Pérez 2 years, 8 months ago 
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.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 include/hw/virtio/vhost-vdpa.h |  1 +
 hw/virtio/vhost-vdpa.c         | 50 ++++++++++++++++++++++++++--------
 2 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
index e98e327f12..6538572a6f 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;
+    size_t n_mr_updated;
     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..512fa18d68 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 +103,25 @@ static void vhost_vdpa_listener_begin(MemoryListener *listener)
     }
 }
 
+static bool vhost_vdpa_iotlb_batch_is_started(const struct vhost_vdpa *v)
+{
+    return v->n_mr_updated != 0;
+}
+
+static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v)
+{
+    if (!vhost_vdpa_iotlb_batch_is_started(v)) {
+        vhost_vdpa_listener_begin_batch(v);
+    }
+
+    v->n_mr_updated++;
+}
+
+static void vhost_vdpa_iotlb_batch_reset(struct vhost_vdpa *v)
+{
+    v->n_mr_updated = 0;
+}
+
 static void vhost_vdpa_listener_commit(MemoryListener *listener)
 {
     struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
@@ -120,6 +133,10 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
         return;
     }
 
+    if (vhost_vdpa_iotlb_batch_is_started(v)) {
+        return;
+    }
+
     msg.type = v->msg_type;
     msg.iotlb.type = VHOST_IOTLB_BATCH_END;
 
@@ -127,6 +144,8 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
         error_report("failed to write, fd=%d, errno=%d (%s)",
                      fd, errno, strerror(errno));
     }
+
+    vhost_vdpa_iotlb_batch_reset(v);
 }
 
 static void vhost_vdpa_listener_region_add(MemoryListener *listener,
@@ -170,6 +189,10 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
 
     llsize = int128_sub(llend, int128_make64(iova));
 
+    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
+        vhost_vdpa_iotlb_batch_begin_once(v);
+    }
+
     ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
                              vaddr, section->readonly);
     if (ret) {
@@ -221,6 +244,10 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
 
     llsize = int128_sub(llend, int128_make64(iova));
 
+    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
+        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 +261,6 @@ 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
Re: [PATCH v2] vhost-vdpa: Do not send empty IOTLB update batches
Posted by Jason Wang 2 years, 8 months ago 
On Thu, Aug 12, 2021 at 12:32 AM 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.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>  include/hw/virtio/vhost-vdpa.h |  1 +
>  hw/virtio/vhost-vdpa.c         | 50 ++++++++++++++++++++++++++--------
>  2 files changed, 39 insertions(+), 12 deletions(-)
>
> diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> index e98e327f12..6538572a6f 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;
> +    size_t n_mr_updated;
>      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..512fa18d68 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 +103,25 @@ static void vhost_vdpa_listener_begin(MemoryListener *listener)
>      }
>  }
>
> +static bool vhost_vdpa_iotlb_batch_is_started(const struct vhost_vdpa *v)
> +{
> +    return v->n_mr_updated != 0;
> +}
> +
> +static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v)
> +{
> +    if (!vhost_vdpa_iotlb_batch_is_started(v)) {
> +        vhost_vdpa_listener_begin_batch(v);
> +    }
> +
> +    v->n_mr_updated++;
> +}
> +
> +static void vhost_vdpa_iotlb_batch_reset(struct vhost_vdpa *v)
> +{
> +    v->n_mr_updated = 0;
> +}
> +
>  static void vhost_vdpa_listener_commit(MemoryListener *listener)
>  {
>      struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
> @@ -120,6 +133,10 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
>          return;
>      }
>
> +    if (vhost_vdpa_iotlb_batch_is_started(v)) {
> +        return;
> +    }
> +
>      msg.type = v->msg_type;
>      msg.iotlb.type = VHOST_IOTLB_BATCH_END;
>
> @@ -127,6 +144,8 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
>          error_report("failed to write, fd=%d, errno=%d (%s)",
>                       fd, errno, strerror(errno));
>      }
> +
> +    vhost_vdpa_iotlb_batch_reset(v);
>  }
>
>  static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> @@ -170,6 +189,10 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
>
>      llsize = int128_sub(llend, int128_make64(iova));
>
> +    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {

Let's move this in to vhost_vdpa_iotlb_batch_begin_once()?

> +        vhost_vdpa_iotlb_batch_begin_once(v);
> +    }
> +
>      ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
>                               vaddr, section->readonly);
>      if (ret) {
> @@ -221,6 +244,10 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
>
>      llsize = int128_sub(llend, int128_make64(iova));
>
> +    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
> +        vhost_vdpa_iotlb_batch_begin_once(v);
> +    }
> +

Do we need to check vhost_vdpa_iotlb_batch_is_started() in the .commit?

Others look good.

Thanks

>      ret = vhost_vdpa_dma_unmap(v, iova, int128_get64(llsize));
>      if (ret) {
>          error_report("vhost_vdpa dma unmap error!");
> @@ -234,7 +261,6 @@ 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
>
Re: [PATCH v2] vhost-vdpa: Do not send empty IOTLB update batches
Posted by Eugenio Perez Martin 2 years, 8 months ago 
On Thu, Aug 12, 2021 at 8:16 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Thu, Aug 12, 2021 at 12:32 AM 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.
> >
> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > ---
> >  include/hw/virtio/vhost-vdpa.h |  1 +
> >  hw/virtio/vhost-vdpa.c         | 50 ++++++++++++++++++++++++++--------
> >  2 files changed, 39 insertions(+), 12 deletions(-)
> >
> > diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> > index e98e327f12..6538572a6f 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;
> > +    size_t n_mr_updated;
> >      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..512fa18d68 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 +103,25 @@ static void vhost_vdpa_listener_begin(MemoryListener *listener)
> >      }
> >  }
> >
> > +static bool vhost_vdpa_iotlb_batch_is_started(const struct vhost_vdpa *v)
> > +{
> > +    return v->n_mr_updated != 0;
> > +}
> > +
> > +static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v)
> > +{
> > +    if (!vhost_vdpa_iotlb_batch_is_started(v)) {
> > +        vhost_vdpa_listener_begin_batch(v);
> > +    }
> > +
> > +    v->n_mr_updated++;
> > +}
> > +
> > +static void vhost_vdpa_iotlb_batch_reset(struct vhost_vdpa *v)
> > +{
> > +    v->n_mr_updated = 0;
> > +}
> > +
> >  static void vhost_vdpa_listener_commit(MemoryListener *listener)
> >  {
> >      struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
> > @@ -120,6 +133,10 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
> >          return;
> >      }
> >
> > +    if (vhost_vdpa_iotlb_batch_is_started(v)) {
> > +        return;
> > +    }
> > +
> >      msg.type = v->msg_type;
> >      msg.iotlb.type = VHOST_IOTLB_BATCH_END;
> >
> > @@ -127,6 +144,8 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
> >          error_report("failed to write, fd=%d, errno=%d (%s)",
> >                       fd, errno, strerror(errno));
> >      }
> > +
> > +    vhost_vdpa_iotlb_batch_reset(v);
> >  }
> >
> >  static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> > @@ -170,6 +189,10 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> >
> >      llsize = int128_sub(llend, int128_make64(iova));
> >
> > +    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
>
> Let's move this in to vhost_vdpa_iotlb_batch_begin_once()?
>

Sure

> > +        vhost_vdpa_iotlb_batch_begin_once(v);
> > +    }
> > +
> >      ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
> >                               vaddr, section->readonly);
> >      if (ret) {
> > @@ -221,6 +244,10 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
> >
> >      llsize = int128_sub(llend, int128_make64(iova));
> >
> > +    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
> > +        vhost_vdpa_iotlb_batch_begin_once(v);
> > +    }
> > +
>
> Do we need to check vhost_vdpa_iotlb_batch_is_started() in the .commit?
>

I don't follow you here. It's that comment in this position of the
patch for a reason?

That checking is the one that allows qemu to skip the IOTLB_END write.

> Others look good.
>
> Thanks
>
> >      ret = vhost_vdpa_dma_unmap(v, iova, int128_get64(llsize));
> >      if (ret) {
> >          error_report("vhost_vdpa dma unmap error!");
> > @@ -234,7 +261,6 @@ 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
> >
>
Re: [PATCH v2] vhost-vdpa: Do not send empty IOTLB update batches
Posted by Jason Wang 2 years, 8 months ago 
On Thu, Aug 12, 2021 at 2:43 PM Eugenio Perez Martin
<eperezma@redhat.com> wrote:
>
> On Thu, Aug 12, 2021 at 8:16 AM Jason Wang <jasowang@redhat.com> wrote:
> >
> > On Thu, Aug 12, 2021 at 12:32 AM 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.
> > >
> > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > > ---
> > >  include/hw/virtio/vhost-vdpa.h |  1 +
> > >  hw/virtio/vhost-vdpa.c         | 50 ++++++++++++++++++++++++++--------
> > >  2 files changed, 39 insertions(+), 12 deletions(-)
> > >
> > > diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> > > index e98e327f12..6538572a6f 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;
> > > +    size_t n_mr_updated;
> > >      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..512fa18d68 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 +103,25 @@ static void vhost_vdpa_listener_begin(MemoryListener *listener)
> > >      }
> > >  }
> > >
> > > +static bool vhost_vdpa_iotlb_batch_is_started(const struct vhost_vdpa *v)
> > > +{
> > > +    return v->n_mr_updated != 0;
> > > +}
> > > +
> > > +static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v)
> > > +{
> > > +    if (!vhost_vdpa_iotlb_batch_is_started(v)) {
> > > +        vhost_vdpa_listener_begin_batch(v);
> > > +    }
> > > +
> > > +    v->n_mr_updated++;
> > > +}
> > > +
> > > +static void vhost_vdpa_iotlb_batch_reset(struct vhost_vdpa *v)
> > > +{
> > > +    v->n_mr_updated = 0;
> > > +}
> > > +
> > >  static void vhost_vdpa_listener_commit(MemoryListener *listener)
> > >  {
> > >      struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
> > > @@ -120,6 +133,10 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
> > >          return;
> > >      }
> > >
> > > +    if (vhost_vdpa_iotlb_batch_is_started(v)) {
> > > +        return;
> > > +    }
> > > +
> > >      msg.type = v->msg_type;
> > >      msg.iotlb.type = VHOST_IOTLB_BATCH_END;
> > >
> > > @@ -127,6 +144,8 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
> > >          error_report("failed to write, fd=%d, errno=%d (%s)",
> > >                       fd, errno, strerror(errno));
> > >      }
> > > +
> > > +    vhost_vdpa_iotlb_batch_reset(v);
> > >  }
> > >
> > >  static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> > > @@ -170,6 +189,10 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> > >
> > >      llsize = int128_sub(llend, int128_make64(iova));
> > >
> > > +    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
> >
> > Let's move this in to vhost_vdpa_iotlb_batch_begin_once()?
> >
>
> Sure
>
> > > +        vhost_vdpa_iotlb_batch_begin_once(v);
> > > +    }
> > > +
> > >      ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
> > >                               vaddr, section->readonly);
> > >      if (ret) {
> > > @@ -221,6 +244,10 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
> > >
> > >      llsize = int128_sub(llend, int128_make64(iova));
> > >
> > > +    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
> > > +        vhost_vdpa_iotlb_batch_begin_once(v);
> > > +    }
> > > +
> >
> > Do we need to check vhost_vdpa_iotlb_batch_is_started() in the .commit?
> >
>
> I don't follow you here. It's that comment in this position of the
> patch for a reason?
>
> That checking is the one that allows qemu to skip the IOTLB_END write.

So it looks to me the BATCH_END will be sent unconditionally in this patch?

If yes, will this become a problem?

Thanks

>
> > Others look good.
> >
> > Thanks
> >
> > >      ret = vhost_vdpa_dma_unmap(v, iova, int128_get64(llsize));
> > >      if (ret) {
> > >          error_report("vhost_vdpa dma unmap error!");
> > > @@ -234,7 +261,6 @@ 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
> > >
> >
>
Re: [PATCH v2] vhost-vdpa: Do not send empty IOTLB update batches
Posted by Eugenio Perez Martin 2 years, 8 months ago 
On Thu, Aug 12, 2021 at 8:45 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Thu, Aug 12, 2021 at 2:43 PM Eugenio Perez Martin
> <eperezma@redhat.com> wrote:
> >
> > On Thu, Aug 12, 2021 at 8:16 AM Jason Wang <jasowang@redhat.com> wrote:
> > >
> > > On Thu, Aug 12, 2021 at 12:32 AM 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.
> > > >
> > > > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > > > ---
> > > >  include/hw/virtio/vhost-vdpa.h |  1 +
> > > >  hw/virtio/vhost-vdpa.c         | 50 ++++++++++++++++++++++++++--------
> > > >  2 files changed, 39 insertions(+), 12 deletions(-)
> > > >
> > > > diff --git a/include/hw/virtio/vhost-vdpa.h b/include/hw/virtio/vhost-vdpa.h
> > > > index e98e327f12..6538572a6f 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;
> > > > +    size_t n_mr_updated;
> > > >      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..512fa18d68 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 +103,25 @@ static void vhost_vdpa_listener_begin(MemoryListener *listener)
> > > >      }
> > > >  }
> > > >
> > > > +static bool vhost_vdpa_iotlb_batch_is_started(const struct vhost_vdpa *v)
> > > > +{
> > > > +    return v->n_mr_updated != 0;
> > > > +}
> > > > +
> > > > +static void vhost_vdpa_iotlb_batch_begin_once(struct vhost_vdpa *v)
> > > > +{
> > > > +    if (!vhost_vdpa_iotlb_batch_is_started(v)) {
> > > > +        vhost_vdpa_listener_begin_batch(v);
> > > > +    }
> > > > +
> > > > +    v->n_mr_updated++;
> > > > +}
> > > > +
> > > > +static void vhost_vdpa_iotlb_batch_reset(struct vhost_vdpa *v)
> > > > +{
> > > > +    v->n_mr_updated = 0;
> > > > +}
> > > > +
> > > >  static void vhost_vdpa_listener_commit(MemoryListener *listener)
> > > >  {
> > > >      struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, listener);
> > > > @@ -120,6 +133,10 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
> > > >          return;
> > > >      }
> > > >
> > > > +    if (vhost_vdpa_iotlb_batch_is_started(v)) {
> > > > +        return;
> > > > +    }
> > > > +
> > > >      msg.type = v->msg_type;
> > > >      msg.iotlb.type = VHOST_IOTLB_BATCH_END;
> > > >
> > > > @@ -127,6 +144,8 @@ static void vhost_vdpa_listener_commit(MemoryListener *listener)
> > > >          error_report("failed to write, fd=%d, errno=%d (%s)",
> > > >                       fd, errno, strerror(errno));
> > > >      }
> > > > +
> > > > +    vhost_vdpa_iotlb_batch_reset(v);
> > > >  }
> > > >
> > > >  static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> > > > @@ -170,6 +189,10 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> > > >
> > > >      llsize = int128_sub(llend, int128_make64(iova));
> > > >
> > > > +    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
> > >
> > > Let's move this in to vhost_vdpa_iotlb_batch_begin_once()?
> > >
> >
> > Sure
> >
> > > > +        vhost_vdpa_iotlb_batch_begin_once(v);
> > > > +    }
> > > > +
> > > >      ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
> > > >                               vaddr, section->readonly);
> > > >      if (ret) {
> > > > @@ -221,6 +244,10 @@ static void vhost_vdpa_listener_region_del(MemoryListener *listener,
> > > >
> > > >      llsize = int128_sub(llend, int128_make64(iova));
> > > >
> > > > +    if (v->dev->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) {
> > > > +        vhost_vdpa_iotlb_batch_begin_once(v);
> > > > +    }
> > > > +
> > >
> > > Do we need to check vhost_vdpa_iotlb_batch_is_started() in the .commit?
> > >
> >
> > I don't follow you here. It's that comment in this position of the
> > patch for a reason?
> >
> > That checking is the one that allows qemu to skip the IOTLB_END write.
>
> So it looks to me the BATCH_END will be sent unconditionally in this patch?
>
> If yes, will this become a problem?
>

Ok so actually the check in .commit needs to be the opposite,
!vhost_vdpa_iotlb_batch_is_started. In my fast testing, the host
notifiers memory regions were the ones actually sending the guest's
memory regions.

Once that testing is negated, it shouldn't send any batches that have
been skipped:

* listener_begin it's not called unconditionally anymore,
* IOTLB_BATCH_BEGIN is only written once in region add/del *if*
section is not skipped and other tests like (iova + len > iova).
* IOTLB_BATCH_END is only written if IOTLB_BATCH_BEGIN has been sent,
that should make vhost_vdpa_iotlb_batch_is_started return true.

Sending the next version with the mentioned changes as v3, please let
me know if I've missed something else.

Thanks!

> Thanks
>
> >
> > > Others look good.
> > >
> > > Thanks
> > >
> > > >      ret = vhost_vdpa_dma_unmap(v, iova, int128_get64(llsize));
> > > >      if (ret) {
> > > >          error_report("vhost_vdpa dma unmap error!");
> > > > @@ -234,7 +261,6 @@ 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
> > > >
> > >
> >
>

Patchew 2.1-devel-0870f84

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