Messages in this thread | | | Subject | Re: [PATCH RFC 4/5] vhost-vdpa: support IOTLB batching hints | From | Jason Wang <> | Date | Mon, 29 Jun 2020 17:26:03 +0800 |
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On 2020/6/28 下午5:58, Michael S. Tsirkin wrote: > On Thu, Jun 18, 2020 at 01:56:25PM +0800, Jason Wang wrote: >> This patches extend the vhost IOTLB API to accept batch updating hints >> form userspace. When userspace wants update the device IOTLB in a >> batch, it may do: >> >> 1) Write vhost_iotlb_msg with VHOST_IOTLB_BATCH_BEGIN flag >> 2) Perform a batch of IOTLB updating via VHOST_IOTLB_UPDATE/INVALIDATE >> 3) Write vhost_iotlb_msg with VHOST_IOTLB_BATCH_END flag > As long as we are extending the interface, > is there some way we could cut down the number of system calls needed > here?
I'm not sure it's worth to do that since usually we only have less than 10 regions.
A possible method is to carry multiple vhost_iotlb_message in one system call.
> > >> Vhost-vdpa may decide to batch the IOMMU/IOTLB updating in step 3 when >> vDPA device support set_map() ops. This is useful for the vDPA device >> that want to know all the mappings to tweak their own DMA translation >> logic. >> >> For vDPA device that doesn't require set_map(), no behavior changes. >> >> This capability is advertised via VHOST_BACKEND_F_IOTLB_BATCH capability. >> >> Signed-off-by: Jason Wang <jasowang@redhat.com> >> --- >> drivers/vhost/vdpa.c | 30 +++++++++++++++++++++++------- >> include/uapi/linux/vhost.h | 2 ++ >> include/uapi/linux/vhost_types.h | 7 +++++++ >> 3 files changed, 32 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c >> index 453057421f80..8f624bbafee7 100644 >> --- a/drivers/vhost/vdpa.c >> +++ b/drivers/vhost/vdpa.c >> @@ -56,7 +56,9 @@ enum { >> }; >> >> enum { >> - VHOST_VDPA_BACKEND_FEATURES = (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2) >> + VHOST_VDPA_BACKEND_FEATURES = >> + (1ULL << VHOST_BACKEND_F_IOTLB_MSG_V2) | >> + (1ULL << VHOST_BACKEND_F_IOTLB_BATCH), >> }; >> >> /* Currently, only network backend w/o multiqueue is supported. */ >> @@ -77,6 +79,7 @@ struct vhost_vdpa { >> int virtio_id; >> int minor; >> struct eventfd_ctx *config_ctx; >> + int in_batch; >> }; >> >> static DEFINE_IDA(vhost_vdpa_ida); >> @@ -125,6 +128,7 @@ static void vhost_vdpa_reset(struct vhost_vdpa *v) >> const struct vdpa_config_ops *ops = vdpa->config; >> >> ops->set_status(vdpa, 0); >> + v->in_batch = 0; >> } >> >> static long vhost_vdpa_get_device_id(struct vhost_vdpa *v, u8 __user *argp) >> @@ -540,9 +544,10 @@ static int vhost_vdpa_map(struct vhost_vdpa *v, >> >> if (ops->dma_map) >> r = ops->dma_map(vdpa, iova, size, pa, perm); >> - else if (ops->set_map) >> - r = ops->set_map(vdpa, dev->iotlb); >> - else >> + else if (ops->set_map) { >> + if (!v->in_batch) >> + r = ops->set_map(vdpa, dev->iotlb); >> + } else >> r = iommu_map(v->domain, iova, pa, size, >> perm_to_iommu_flags(perm)); >> >> @@ -559,9 +564,10 @@ static void vhost_vdpa_unmap(struct vhost_vdpa *v, u64 iova, u64 size) >> >> if (ops->dma_map) >> ops->dma_unmap(vdpa, iova, size); >> - else if (ops->set_map) >> - ops->set_map(vdpa, dev->iotlb); >> - else >> + else if (ops->set_map) { >> + if (!v->in_batch) >> + ops->set_map(vdpa, dev->iotlb); >> + } else >> iommu_unmap(v->domain, iova, size); >> } >> >> @@ -655,6 +661,8 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev, >> struct vhost_iotlb_msg *msg) >> { >> struct vhost_vdpa *v = container_of(dev, struct vhost_vdpa, vdev); >> + struct vdpa_device *vdpa = v->vdpa; >> + const struct vdpa_config_ops *ops = vdpa->config; >> int r = 0; >> >> r = vhost_dev_check_owner(dev); >> @@ -668,6 +676,14 @@ static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev, >> case VHOST_IOTLB_INVALIDATE: >> vhost_vdpa_unmap(v, msg->iova, msg->size); >> break; >> + case VHOST_IOTLB_BATCH_BEGIN: >> + v->in_batch = true; >> + break; >> + case VHOST_IOTLB_BATCH_END: >> + if (v->in_batch && ops->set_map) >> + ops->set_map(vdpa, dev->iotlb); >> + v->in_batch = false; >> + break; >> default: >> r = -EINVAL; >> break; >> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h >> index 0c2349612e77..565da96f55d5 100644 >> --- a/include/uapi/linux/vhost.h >> +++ b/include/uapi/linux/vhost.h >> @@ -91,6 +91,8 @@ >> >> /* Use message type V2 */ >> #define VHOST_BACKEND_F_IOTLB_MSG_V2 0x1 >> +/* IOTLB can accpet batching hints */ > typo
Will fix.
> >> +#define VHOST_BACKEND_F_IOTLB_BATCH 0x2 >> >> #define VHOST_SET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x25, __u64) >> #define VHOST_GET_BACKEND_FEATURES _IOR(VHOST_VIRTIO, 0x26, __u64) >> diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h >> index 669457ce5c48..5c12faffdde9 100644 >> --- a/include/uapi/linux/vhost_types.h >> +++ b/include/uapi/linux/vhost_types.h >> @@ -60,6 +60,13 @@ struct vhost_iotlb_msg { >> #define VHOST_IOTLB_UPDATE 2 >> #define VHOST_IOTLB_INVALIDATE 3 >> #define VHOST_IOTLB_ACCESS_FAIL 4 >> +/* VHOST_IOTLB_BATCH_BEGIN is a hint that userspace will update >> + * several mappings afterwards. VHOST_IOTLB_BATCH_END is a hint that >> + * userspace had finished the mapping updating. > > Well not just hints - in fact updates do not take place > until _END. > > How about: > > /* VHOST_IOTLB_BATCH_BEGIN and VHOST_IOTLB_BATCH_END allow modifying > * multiple mappings in one go: beginning with > * VHOST_IOTLB_BATCH_BEGIN, followed by any number of > VHOST_IOTLB_UPDATE messages, and ending with VHOST_IOTLB_BATCH_END. > */
That's better.
> > >> When those two flags >> + * were set, kernel will ignore the rest fileds of the IOTLB message. > how about: > > when one of these two values is used as the message type, the > rest of the fields in the message are ignored.
Yes.
Will fix.
Thanks
> >> + */ >> +#define VHOST_IOTLB_BATCH_BEGIN 5 >> +#define VHOST_IOTLB_BATCH_END 6 >> __u8 type; >> }; >> >> -- >> 2.20.1
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