Re: [RFC PATCH v4 20/20] vdpa: Add custom IOTLB translations to SVQ

[Jason Wang <jasowang@redhat.com>]

在 2021/10/1 下午3:06, Eugenio Pérez 写道:
> Use translations added in VhostIOVATree in SVQ.
>
> Now every element needs to store the previous address also, so VirtQueue
> can consume the elements properly. This adds a little overhead per VQ
> element, having to allocate more memory to stash them. As a possible
> optimization, this allocation could be avoided if the descriptor is not
> a chain but a single one, but this is left undone.
>
> TODO: iova range should be queried before, and add logic to fail when
> GPA is outside of its range and memory listener or svq add it.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
>   hw/virtio/vhost-shadow-virtqueue.h |   4 +-
>   hw/virtio/vhost-shadow-virtqueue.c | 130 ++++++++++++++++++++++++-----
>   hw/virtio/vhost-vdpa.c             |  40 ++++++++-
>   hw/virtio/trace-events             |   1 +
>   4 files changed, 152 insertions(+), 23 deletions(-)
>
> diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
> index b7baa424a7..a0e6b5267a 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.h
> +++ b/hw/virtio/vhost-shadow-virtqueue.h
> @@ -11,6 +11,7 @@
>   #define VHOST_SHADOW_VIRTQUEUE_H
>   
>   #include "hw/virtio/vhost.h"
> +#include "hw/virtio/vhost-iova-tree.h"
>   
>   typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
>   
> @@ -28,7 +29,8 @@ bool vhost_svq_start(struct vhost_dev *dev, unsigned idx,
>   void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
>                       VhostShadowVirtqueue *svq);
>   
> -VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx);
> +VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx,
> +                                    VhostIOVATree *iova_map);
>   
>   void vhost_svq_free(VhostShadowVirtqueue *vq);
>   
> diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
> index 2fd0bab75d..9db538547e 100644
> --- a/hw/virtio/vhost-shadow-virtqueue.c
> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> @@ -11,12 +11,19 @@
>   #include "hw/virtio/vhost-shadow-virtqueue.h"
>   #include "hw/virtio/vhost.h"
>   #include "hw/virtio/virtio-access.h"
> +#include "hw/virtio/vhost-iova-tree.h"
>   
>   #include "standard-headers/linux/vhost_types.h"
>   
>   #include "qemu/error-report.h"
>   #include "qemu/main-loop.h"
>   
> +typedef struct SVQElement {
> +    VirtQueueElement elem;
> +    void **in_sg_stash;
> +    void **out_sg_stash;
> +} SVQElement;
> +
>   /* Shadow virtqueue to relay notifications */
>   typedef struct VhostShadowVirtqueue {
>       /* Shadow vring */
> @@ -46,8 +53,11 @@ typedef struct VhostShadowVirtqueue {
>       /* Virtio device */
>       VirtIODevice *vdev;
>   
> +    /* IOVA mapping if used */
> +    VhostIOVATree *iova_map;
> +
>       /* Map for returning guest's descriptors */
> -    VirtQueueElement **ring_id_maps;
> +    SVQElement **ring_id_maps;
>   
>       /* Next head to expose to device */
>       uint16_t avail_idx_shadow;
> @@ -79,13 +89,6 @@ bool vhost_svq_valid_device_features(uint64_t *dev_features)
>               continue;
>   
>           case VIRTIO_F_ACCESS_PLATFORM:
> -            /* SVQ needs this feature disabled. Can't continue */
> -            if (*dev_features & BIT_ULL(b)) {
> -                clear_bit(b, dev_features);
> -                r = false;
> -            }
> -            break;
> -
>           case VIRTIO_F_VERSION_1:
>               /* SVQ needs this feature, so can't continue */
>               if (!(*dev_features & BIT_ULL(b))) {
> @@ -126,6 +129,64 @@ static void vhost_svq_set_notification(VhostShadowVirtqueue *svq, bool enable)
>       }
>   }
>   
> +static void vhost_svq_stash_addr(void ***stash, const struct iovec *iov,
> +                                 size_t num)
> +{
> +    size_t i;
> +
> +    if (num == 0) {
> +        return;
> +    }
> +
> +    *stash = g_new(void *, num);
> +    for (i = 0; i < num; ++i) {
> +        (*stash)[i] = iov[i].iov_base;
> +    }
> +}
> +
> +static void vhost_svq_unstash_addr(void **stash, struct iovec *iov, size_t num)
> +{
> +    size_t i;
> +
> +    if (num == 0) {
> +        return;
> +    }
> +
> +    for (i = 0; i < num; ++i) {
> +        iov[i].iov_base = stash[i];
> +    }
> +    g_free(stash);
> +}
> +
> +static void vhost_svq_translate_addr(const VhostShadowVirtqueue *svq,
> +                                     struct iovec *iovec, size_t num)
> +{
> +    size_t i;
> +
> +    for (i = 0; i < num; ++i) {
> +        VhostDMAMap needle = {
> +            .translated_addr = iovec[i].iov_base,
> +            .size = iovec[i].iov_len,
> +        };
> +        size_t off;
> +
> +        const VhostDMAMap *map = vhost_iova_tree_find_iova(svq->iova_map,
> +                                                           &needle);


Is it possible that we end up with more than one maps here?


> +        /*
> +         * Map cannot be NULL since iova map contains all guest space and
> +         * qemu already has a physical address mapped
> +         */
> +        assert(map);
> +
> +        /*
> +         * Map->iova chunk size is ignored. What to do if descriptor
> +         * (addr, size) does not fit is delegated to the device.
> +         */
> +        off = needle.translated_addr - map->translated_addr;
> +        iovec[i].iov_base = (void *)(map->iova + off);
> +    }
> +}
> +
>   static void vhost_vring_write_descs(VhostShadowVirtqueue *svq,
>                                       const struct iovec *iovec,
>                                       size_t num, bool more_descs, bool write)
> @@ -156,8 +217,9 @@ static void vhost_vring_write_descs(VhostShadowVirtqueue *svq,
>   }
>   
>   static unsigned vhost_svq_add_split(VhostShadowVirtqueue *svq,
> -                                    VirtQueueElement *elem)
> +                                    SVQElement *svq_elem)
>   {
> +    VirtQueueElement *elem = &svq_elem->elem;
>       int head;
>       unsigned avail_idx;
>       vring_avail_t *avail = svq->vring.avail;
> @@ -167,6 +229,12 @@ static unsigned vhost_svq_add_split(VhostShadowVirtqueue *svq,
>       /* We need some descriptors here */
>       assert(elem->out_num || elem->in_num);
>   
> +    vhost_svq_stash_addr(&svq_elem->in_sg_stash, elem->in_sg, elem->in_num);
> +    vhost_svq_stash_addr(&svq_elem->out_sg_stash, elem->out_sg, elem->out_num);


I wonder if we can solve the trick like stash and unstash with a 
dedicated sgs in svq_elem, instead of reusing the elem.

Thanks


> +
> +    vhost_svq_translate_addr(svq, elem->in_sg, elem->in_num);
> +    vhost_svq_translate_addr(svq, elem->out_sg, elem->out_num);
> +
>       vhost_vring_write_descs(svq, elem->out_sg, elem->out_num,
>                               elem->in_num > 0, false);
>       vhost_vring_write_descs(svq, elem->in_sg, elem->in_num, false, true);
> @@ -187,7 +255,7 @@ static unsigned vhost_svq_add_split(VhostShadowVirtqueue *svq,
>   
>   }
>   
> -static void vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement *elem)
> +static void vhost_svq_add(VhostShadowVirtqueue *svq, SVQElement *elem)
>   {
>       unsigned qemu_head = vhost_svq_add_split(svq, elem);
>   
> @@ -221,7 +289,7 @@ static void vhost_handle_guest_kick(EventNotifier *n)
>           }
>   
>           while (true) {
> -            VirtQueueElement *elem = virtqueue_pop(svq->vq, sizeof(*elem));
> +            SVQElement *elem = virtqueue_pop(svq->vq, sizeof(*elem));
>               if (!elem) {
>                   break;
>               }
> @@ -247,7 +315,7 @@ static bool vhost_svq_more_used(VhostShadowVirtqueue *svq)
>       return svq->used_idx != svq->shadow_used_idx;
>   }
>   
> -static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq)
> +static SVQElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq)
>   {
>       vring_desc_t *descs = svq->vring.desc;
>       const vring_used_t *used = svq->vring.used;
> @@ -279,7 +347,7 @@ static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq)
>       descs[used_elem.id].next = svq->free_head;
>       svq->free_head = used_elem.id;
>   
> -    svq->ring_id_maps[used_elem.id]->len = used_elem.len;
> +    svq->ring_id_maps[used_elem.id]->elem.len = used_elem.len;
>       return g_steal_pointer(&svq->ring_id_maps[used_elem.id]);
>   }
>   
> @@ -296,12 +364,19 @@ static void vhost_svq_handle_call_no_test(EventNotifier *n)
>   
>           vhost_svq_set_notification(svq, false);
>           while (true) {
> -            g_autofree VirtQueueElement *elem = vhost_svq_get_buf(svq);
> -            if (!elem) {
> +            g_autofree SVQElement *svq_elem = vhost_svq_get_buf(svq);
> +            VirtQueueElement *elem;
> +            if (!svq_elem) {
>                   break;
>               }
>   
>               assert(i < svq->vring.num);
> +            elem = &svq_elem->elem;
> +
> +            vhost_svq_unstash_addr(svq_elem->in_sg_stash, elem->in_sg,
> +                                   elem->in_num);
> +            vhost_svq_unstash_addr(svq_elem->out_sg_stash, elem->out_sg,
> +                                   elem->out_num);
>               virtqueue_fill(vq, elem, elem->len, i++);
>           }
>   
> @@ -451,14 +526,24 @@ void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
>       event_notifier_set_handler(&svq->host_notifier, NULL);
>   
>       for (i = 0; i < svq->vring.num; ++i) {
> -        g_autofree VirtQueueElement *elem = svq->ring_id_maps[i];
> +        g_autofree SVQElement *svq_elem = svq->ring_id_maps[i];
> +        VirtQueueElement *elem;
> +
> +        if (!svq_elem) {
> +            continue;
> +        }
> +
> +        elem = &svq_elem->elem;
> +        vhost_svq_unstash_addr(svq_elem->in_sg_stash, elem->in_sg,
> +                               elem->in_num);
> +        vhost_svq_unstash_addr(svq_elem->out_sg_stash, elem->out_sg,
> +                               elem->out_num);
> +
>           /*
>            * Although the doc says we must unpop in order, it's ok to unpop
>            * everything.
>            */
> -        if (elem) {
> -            virtqueue_unpop(svq->vq, elem, elem->len);
> -        }
> +        virtqueue_unpop(svq->vq, elem, elem->len);
>       }
>   }
>   
> @@ -466,7 +551,8 @@ void vhost_svq_stop(struct vhost_dev *dev, unsigned idx,
>    * Creates vhost shadow virtqueue, and instruct vhost device to use the shadow
>    * methods and file descriptors.
>    */
> -VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
> +VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx,
> +                                    VhostIOVATree *iova_map)
>   {
>       int vq_idx = dev->vq_index + idx;
>       unsigned num = virtio_queue_get_num(dev->vdev, vq_idx);
> @@ -500,11 +586,13 @@ VhostShadowVirtqueue *vhost_svq_new(struct vhost_dev *dev, int idx)
>       memset(svq->vring.desc, 0, driver_size);
>       svq->vring.used = qemu_memalign(qemu_real_host_page_size, device_size);
>       memset(svq->vring.used, 0, device_size);
> +    svq->iova_map = iova_map;
> +
>       for (i = 0; i < num - 1; i++) {
>           svq->vring.desc[i].next = cpu_to_le16(i + 1);
>       }
>   
> -    svq->ring_id_maps = g_new0(VirtQueueElement *, num);
> +    svq->ring_id_maps = g_new0(SVQElement *, num);
>       event_notifier_set_handler(&svq->call_notifier,
>                                  vhost_svq_handle_call);
>       return g_steal_pointer(&svq);
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index a9c680b487..f5a12fee9d 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -176,6 +176,18 @@ static void vhost_vdpa_listener_region_add(MemoryListener *listener,
>                                            vaddr, section->readonly);
>   
>       llsize = int128_sub(llend, int128_make64(iova));
> +    if (v->shadow_vqs_enabled) {
> +        VhostDMAMap mem_region = {
> +            .translated_addr = vaddr,
> +            .size = int128_get64(llsize) - 1,
> +            .perm = IOMMU_ACCESS_FLAG(true, section->readonly),
> +        };
> +
> +        int r = vhost_iova_tree_alloc(v->iova_map, &mem_region);
> +        assert(r == VHOST_DMA_MAP_OK);
> +
> +        iova = mem_region.iova;
> +    }
>   
>       ret = vhost_vdpa_dma_map(v, iova, int128_get64(llsize),
>                                vaddr, section->readonly);
> @@ -754,6 +766,23 @@ static bool  vhost_vdpa_force_iommu(struct vhost_dev *dev)
>       return true;
>   }
>   
> +static int vhost_vdpa_get_iova_range(struct vhost_dev *dev,
> +                                     hwaddr *first, hwaddr *last)
> +{
> +    int ret;
> +    struct vhost_vdpa_iova_range range;
> +
> +    ret = vhost_vdpa_call(dev, VHOST_VDPA_GET_IOVA_RANGE, &range);
> +    if (ret != 0) {
> +        return ret;
> +    }
> +
> +    *first = range.first;
> +    *last = range.last;
> +    trace_vhost_vdpa_get_iova_range(dev, *first, *last);
> +    return ret;
> +}
> +
>   /**
>    * Maps QEMU vaddr memory to device in a suitable way for shadow virtqueue:
>    * - It always reference qemu memory address, not guest's memory.
> @@ -881,6 +910,7 @@ static bool vhost_vdpa_svq_start_vq(struct vhost_dev *dev, unsigned idx)
>   static unsigned vhost_vdpa_enable_svq(struct vhost_vdpa *v, bool enable)
>   {
>       struct vhost_dev *hdev = v->dev;
> +    hwaddr iova_first, iova_last;
>       unsigned n;
>       int r;
>   
> @@ -894,7 +924,7 @@ static unsigned vhost_vdpa_enable_svq(struct vhost_vdpa *v, bool enable)
>           /* Allocate resources */
>           assert(v->shadow_vqs->len == 0);
>           for (n = 0; n < hdev->nvqs; ++n) {
> -            VhostShadowVirtqueue *svq = vhost_svq_new(hdev, n);
> +            VhostShadowVirtqueue *svq = vhost_svq_new(hdev, n, v->iova_map);
>               if (unlikely(!svq)) {
>                   g_ptr_array_set_size(v->shadow_vqs, 0);
>                   return 0;
> @@ -903,6 +933,8 @@ static unsigned vhost_vdpa_enable_svq(struct vhost_vdpa *v, bool enable)
>           }
>       }
>   
> +    r = vhost_vdpa_get_iova_range(hdev, &iova_first, &iova_last);
> +    assert(r == 0);
>       r = vhost_vdpa_vring_pause(hdev);
>       assert(r == 0);
>   
> @@ -913,6 +945,12 @@ static unsigned vhost_vdpa_enable_svq(struct vhost_vdpa *v, bool enable)
>           }
>       }
>   
> +    memory_listener_unregister(&v->listener);
> +    if (vhost_vdpa_dma_unmap(v, iova_first,
> +                             (iova_last - iova_first) & TARGET_PAGE_MASK)) {
> +        error_report("Fail to invalidate device iotlb");
> +    }
> +
>       /* Reset device so it can be configured */
>       r = vhost_vdpa_dev_start(hdev, false);
>       assert(r == 0);
> diff --git a/hw/virtio/trace-events b/hw/virtio/trace-events
> index 8ed19e9d0c..650e521e35 100644
> --- a/hw/virtio/trace-events
> +++ b/hw/virtio/trace-events
> @@ -52,6 +52,7 @@ vhost_vdpa_set_vring_call(void *dev, unsigned int index, int fd) "dev: %p index:
>   vhost_vdpa_get_features(void *dev, uint64_t features) "dev: %p features: 0x%"PRIx64
>   vhost_vdpa_set_owner(void *dev) "dev: %p"
>   vhost_vdpa_vq_get_addr(void *dev, void *vq, uint64_t desc_user_addr, uint64_t avail_user_addr, uint64_t used_user_addr) "dev: %p vq: %p desc_user_addr: 0x%"PRIx64" avail_user_addr: 0x%"PRIx64" used_user_addr: 0x%"PRIx64
> +vhost_vdpa_get_iova_range(void *dev, uint64_t first, uint64_t last) "dev: %p first: 0x%"PRIx64" last: 0x%"PRIx64
>   
>   # virtio.c
>   virtqueue_alloc_element(void *elem, size_t sz, unsigned in_num, unsigned out_num) "elem %p size %zd in_num %u out_num %u"