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Re: [PATCH 18/31] vhost: Shadow virtqueue buffers forwarding
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From: |
Eugenio Perez Martin |
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Subject: |
Re: [PATCH 18/31] vhost: Shadow virtqueue buffers forwarding |
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Date: |
Tue, 22 Feb 2022 20:01:03 +0100 |
On Tue, Feb 8, 2022 at 9:11 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2022/2/2 上午1:08, Eugenio Perez Martin 写道:
> > On Sun, Jan 30, 2022 at 5:43 AM Jason Wang <jasowang@redhat.com> wrote:
> >>
> >> 在 2022/1/22 上午4:27, Eugenio Pérez 写道:
> >>> Initial version of shadow virtqueue that actually forward buffers. There
> >>> is no iommu support at the moment, and that will be addressed in future
> >>> patches of this series. Since all vhost-vdpa devices use forced IOMMU,
> >>> this means that SVQ is not usable at this point of the series on any
> >>> device.
> >>>
> >>> For simplicity it only supports modern devices, that expects vring
> >>> in little endian, with split ring and no event idx or indirect
> >>> descriptors. Support for them will not be added in this series.
> >>>
> >>> It reuses the VirtQueue code for the device part. The driver part is
> >>> based on Linux's virtio_ring driver, but with stripped functionality
> >>> and optimizations so it's easier to review.
> >>>
> >>> However, forwarding buffers have some particular pieces: One of the most
> >>> unexpected ones is that a guest's buffer can expand through more than
> >>> one descriptor in SVQ. While this is handled gracefully by qemu's
> >>> emulated virtio devices, it may cause unexpected SVQ queue full. This
> >>> patch also solves it by checking for this condition at both guest's
> >>> kicks and device's calls. The code may be more elegant in the future if
> >>> SVQ code runs in its own iocontext.
> >>>
> >>> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> >>> ---
> >>> hw/virtio/vhost-shadow-virtqueue.h | 2 +
> >>> hw/virtio/vhost-shadow-virtqueue.c | 365 ++++++++++++++++++++++++++++-
> >>> hw/virtio/vhost-vdpa.c | 111 ++++++++-
> >>> 3 files changed, 462 insertions(+), 16 deletions(-)
> >>>
> >>> diff --git a/hw/virtio/vhost-shadow-virtqueue.h
> >>> b/hw/virtio/vhost-shadow-virtqueue.h
> >>> index 39aef5ffdf..19c934af49 100644
> >>> --- a/hw/virtio/vhost-shadow-virtqueue.h
> >>> +++ b/hw/virtio/vhost-shadow-virtqueue.h
> >>> @@ -33,6 +33,8 @@ uint16_t vhost_svq_get_num(const VhostShadowVirtqueue
> >>> *svq);
> >>> size_t vhost_svq_driver_area_size(const VhostShadowVirtqueue *svq);
> >>> size_t vhost_svq_device_area_size(const VhostShadowVirtqueue *svq);
> >>>
> >>> +void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
> >>> + VirtQueue *vq);
> >>> void vhost_svq_stop(VhostShadowVirtqueue *svq);
> >>>
> >>> VhostShadowVirtqueue *vhost_svq_new(uint16_t qsize);
> >>> diff --git a/hw/virtio/vhost-shadow-virtqueue.c
> >>> b/hw/virtio/vhost-shadow-virtqueue.c
> >>> index 7c168075d7..a1a404f68f 100644
> >>> --- a/hw/virtio/vhost-shadow-virtqueue.c
> >>> +++ b/hw/virtio/vhost-shadow-virtqueue.c
> >>> @@ -9,6 +9,8 @@
> >>>
> >>> #include "qemu/osdep.h"
> >>> #include "hw/virtio/vhost-shadow-virtqueue.h"
> >>> +#include "hw/virtio/vhost.h"
> >>> +#include "hw/virtio/virtio-access.h"
> >>> #include "standard-headers/linux/vhost_types.h"
> >>>
> >>> #include "qemu/error-report.h"
> >>> @@ -36,6 +38,33 @@ typedef struct VhostShadowVirtqueue {
> >>>
> >>> /* Guest's call notifier, where SVQ calls guest. */
> >>> EventNotifier svq_call;
> >>> +
> >>> + /* Virtio queue shadowing */
> >>> + VirtQueue *vq;
> >>> +
> >>> + /* Virtio device */
> >>> + VirtIODevice *vdev;
> >>> +
> >>> + /* Map for returning guest's descriptors */
> >>> + VirtQueueElement **ring_id_maps;
> >>> +
> >>> + /* Next VirtQueue element that guest made available */
> >>> + VirtQueueElement *next_guest_avail_elem;
> >>> +
> >>> + /* Next head to expose to device */
> >>> + uint16_t avail_idx_shadow;
> >>> +
> >>> + /* Next free descriptor */
> >>> + uint16_t free_head;
> >>> +
> >>> + /* Last seen used idx */
> >>> + uint16_t shadow_used_idx;
> >>> +
> >>> + /* Next head to consume from device */
> >>> + uint16_t last_used_idx;
> >>> +
> >>> + /* Cache for the exposed notification flag */
> >>> + bool notification;
> >>> } VhostShadowVirtqueue;
> >>>
> >>> #define INVALID_SVQ_KICK_FD -1
> >>> @@ -148,30 +177,294 @@ bool vhost_svq_ack_guest_features(uint64_t
> >>> dev_features,
> >>> return true;
> >>> }
> >>>
> >>> -/* Forward guest notifications */
> >>> -static void vhost_handle_guest_kick(EventNotifier *n)
> >>> +/**
> >>> + * Number of descriptors that SVQ can make available from the guest.
> >>> + *
> >>> + * @svq The svq
> >>> + */
> >>> +static uint16_t vhost_svq_available_slots(const VhostShadowVirtqueue
> >>> *svq)
> >>> {
> >>> - VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue,
> >>> - svq_kick);
> >>> + return svq->vring.num - (svq->avail_idx_shadow -
> >>> svq->shadow_used_idx);
> >>> +}
> >>> +
> >>> +static void vhost_svq_set_notification(VhostShadowVirtqueue *svq, bool
> >>> enable)
> >>> +{
> >>> + uint16_t notification_flag;
> >>>
> >>> - if (unlikely(!event_notifier_test_and_clear(n))) {
> >>> + if (svq->notification == enable) {
> >>> + return;
> >>> + }
> >>> +
> >>> + notification_flag = cpu_to_le16(VRING_AVAIL_F_NO_INTERRUPT);
> >>> +
> >>> + svq->notification = enable;
> >>> + if (enable) {
> >>> + svq->vring.avail->flags &= ~notification_flag;
> >>> + } else {
> >>> + svq->vring.avail->flags |= notification_flag;
> >>> + }
> >>> +}
> >>> +
> >>> +static void vhost_vring_write_descs(VhostShadowVirtqueue *svq,
> >>> + const struct iovec *iovec,
> >>> + size_t num, bool more_descs, bool
> >>> write)
> >>> +{
> >>> + uint16_t i = svq->free_head, last = svq->free_head;
> >>> + unsigned n;
> >>> + uint16_t flags = write ? cpu_to_le16(VRING_DESC_F_WRITE) : 0;
> >>> + vring_desc_t *descs = svq->vring.desc;
> >>> +
> >>> + if (num == 0) {
> >>> + return;
> >>> + }
> >>> +
> >>> + for (n = 0; n < num; n++) {
> >>> + if (more_descs || (n + 1 < num)) {
> >>> + descs[i].flags = flags | cpu_to_le16(VRING_DESC_F_NEXT);
> >>> + } else {
> >>> + descs[i].flags = flags;
> >>> + }
> >>> + descs[i].addr = cpu_to_le64((hwaddr)iovec[n].iov_base);
> >>> + descs[i].len = cpu_to_le32(iovec[n].iov_len);
> >>> +
> >>> + last = i;
> >>> + i = cpu_to_le16(descs[i].next);
> >>> + }
> >>> +
> >>> + svq->free_head = le16_to_cpu(descs[last].next);
> >>> +}
> >>> +
> >>> +static unsigned vhost_svq_add_split(VhostShadowVirtqueue *svq,
> >>> + VirtQueueElement *elem)
> >>> +{
> >>> + int head;
> >>> + unsigned avail_idx;
> >>> + vring_avail_t *avail = svq->vring.avail;
> >>> +
> >>> + head = svq->free_head;
> >>> +
> >>> + /* We need some descriptors here */
> >>> + assert(elem->out_num || elem->in_num);
> >>
> >> Looks like this could be triggered by guest, we need fail instead assert
> >> here.
> >>
> > My understanding was that virtqueue_pop already sanitized that case,
> > but I'm not able to find where now. I will recheck and, in case it's
> > not, I will move to a failure.
> >
> >>> +
> >>> + 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);
> >>> +
> >>> + /*
> >>> + * Put entry in available array (but don't update avail->idx until
> >>> they
> >>> + * do sync).
> >>> + */
> >>> + avail_idx = svq->avail_idx_shadow & (svq->vring.num - 1);
> >>> + avail->ring[avail_idx] = cpu_to_le16(head);
> >>> + svq->avail_idx_shadow++;
> >>> +
> >>> + /* Update avail index after the descriptor is wrote */
> >>> + smp_wmb();
> >>> + avail->idx = cpu_to_le16(svq->avail_idx_shadow);
> >>> +
> >>> + return head;
> >>> +}
> >>> +
> >>> +static void vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement
> >>> *elem)
> >>> +{
> >>> + unsigned qemu_head = vhost_svq_add_split(svq, elem);
> >>> +
> >>> + svq->ring_id_maps[qemu_head] = elem;
> >>> +}
> >>> +
> >>> +static void vhost_svq_kick(VhostShadowVirtqueue *svq)
> >>> +{
> >>> + /* We need to expose available array entries before checking used
> >>> flags */
> >>> + smp_mb();
> >>> + if (svq->vring.used->flags & VRING_USED_F_NO_NOTIFY) {
> >>> return;
> >>> }
> >>>
> >>> event_notifier_set(&svq->hdev_kick);
> >>> }
> >>>
> >>> -/* Forward vhost notifications */
> >>> +/**
> >>> + * Forward available buffers.
> >>> + *
> >>> + * @svq Shadow VirtQueue
> >>> + *
> >>> + * Note that this function does not guarantee that all guest's available
> >>> + * buffers are available to the device in SVQ avail ring. The guest may
> >>> have
> >>> + * exposed a GPA / GIOVA congiuous buffer, but it may not be contiguous
> >>> in qemu
> >>> + * vaddr.
> >>> + *
> >>> + * If that happens, guest's kick notifications will be disabled until
> >>> device
> >>> + * makes some buffers used.
> >>> + */
> >>> +static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
> >>> +{
> >>> + /* Clear event notifier */
> >>> + event_notifier_test_and_clear(&svq->svq_kick);
> >>> +
> >>> + /* Make available as many buffers as possible */
> >>> + do {
> >>> + if (virtio_queue_get_notification(svq->vq)) {
> >>> + virtio_queue_set_notification(svq->vq, false);
> >>
> >> This looks like an optimization the should belong to
> >> virtio_queue_set_notification() itself.
> >>
> > Sure we can move.
> >
> >>> + }
> >>> +
> >>> + while (true) {
> >>> + VirtQueueElement *elem;
> >>> +
> >>> + if (svq->next_guest_avail_elem) {
> >>> + elem = g_steal_pointer(&svq->next_guest_avail_elem);
> >>> + } else {
> >>> + elem = virtqueue_pop(svq->vq, sizeof(*elem));
> >>> + }
> >>> +
> >>> + if (!elem) {
> >>> + break;
> >>> + }
> >>> +
> >>> + if (elem->out_num + elem->in_num >
> >>> + vhost_svq_available_slots(svq)) {
> >>> + /*
> >>> + * This condition is possible since a contiguous buffer
> >>> in GPA
> >>> + * does not imply a contiguous buffer in qemu's VA
> >>> + * scatter-gather segments. If that happen, the buffer
> >>> exposed
> >>> + * to the device needs to be a chain of descriptors at
> >>> this
> >>> + * moment.
> >>> + *
> >>> + * SVQ cannot hold more available buffers if we are here:
> >>> + * queue the current guest descriptor and ignore further
> >>> kicks
> >>> + * until some elements are used.
> >>> + */
> >>> + svq->next_guest_avail_elem = elem;
> >>> + return;
> >>> + }
> >>> +
> >>> + vhost_svq_add(svq, elem);
> >>> + vhost_svq_kick(svq);
> >>> + }
> >>> +
> >>> + virtio_queue_set_notification(svq->vq, true);
> >>> + } while (!virtio_queue_empty(svq->vq));
> >>> +}
> >>> +
> >>> +/**
> >>> + * Handle guest's kick.
> >>> + *
> >>> + * @n guest kick event notifier, the one that guest set to notify svq.
> >>> + */
> >>> +static void vhost_handle_guest_kick_notifier(EventNotifier *n)
> >>> +{
> >>> + VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue,
> >>> + svq_kick);
> >>> + vhost_handle_guest_kick(svq);
> >>> +}
> >>> +
> >>> +static bool vhost_svq_more_used(VhostShadowVirtqueue *svq)
> >>> +{
> >>> + if (svq->last_used_idx != svq->shadow_used_idx) {
> >>> + return true;
> >>> + }
> >>> +
> >>> + svq->shadow_used_idx = cpu_to_le16(svq->vring.used->idx);
> >>> +
> >>> + return svq->last_used_idx != svq->shadow_used_idx;
> >>> +}
> >>> +
> >>> +static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq)
> >>> +{
> >>> + vring_desc_t *descs = svq->vring.desc;
> >>> + const vring_used_t *used = svq->vring.used;
> >>> + vring_used_elem_t used_elem;
> >>> + uint16_t last_used;
> >>> +
> >>> + if (!vhost_svq_more_used(svq)) {
> >>> + return NULL;
> >>> + }
> >>> +
> >>> + /* Only get used array entries after they have been exposed by dev */
> >>> + smp_rmb();
> >>> + last_used = svq->last_used_idx & (svq->vring.num - 1);
> >>> + used_elem.id = le32_to_cpu(used->ring[last_used].id);
> >>> + used_elem.len = le32_to_cpu(used->ring[last_used].len);
> >>> +
> >>> + svq->last_used_idx++;
> >>> + if (unlikely(used_elem.id >= svq->vring.num)) {
> >>> + error_report("Device %s says index %u is used", svq->vdev->name,
> >>> + used_elem.id);
> >>> + return NULL;
> >>> + }
> >>> +
> >>> + if (unlikely(!svq->ring_id_maps[used_elem.id])) {
> >>> + error_report(
> >>> + "Device %s says index %u is used, but it was not available",
> >>> + svq->vdev->name, used_elem.id);
> >>> + return NULL;
> >>> + }
> >>> +
> >>> + 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;
> >>> + return g_steal_pointer(&svq->ring_id_maps[used_elem.id]);
> >>> +}
> >>> +
> >>> +static void vhost_svq_flush(VhostShadowVirtqueue *svq,
> >>> + bool check_for_avail_queue)
> >>> +{
> >>> + VirtQueue *vq = svq->vq;
> >>> +
> >>> + /* Make as many buffers as possible used. */
> >>> + do {
> >>> + unsigned i = 0;
> >>> +
> >>> + vhost_svq_set_notification(svq, false);
> >>> + while (true) {
> >>> + g_autofree VirtQueueElement *elem = vhost_svq_get_buf(svq);
> >>> + if (!elem) {
> >>> + break;
> >>> + }
> >>> +
> >>> + if (unlikely(i >= svq->vring.num)) {
> >>> + virtio_error(svq->vdev,
> >>> + "More than %u used buffers obtained in a %u
> >>> size SVQ",
> >>> + i, svq->vring.num);
> >>> + virtqueue_fill(vq, elem, elem->len, i);
> >>> + virtqueue_flush(vq, i);
> >>
> >> Let's simply use virtqueue_push() here?
> >>
> > virtqueue_push support to fill and flush only one element, instead of
> > batch. I'm fine with either but I think the less updates to the used
> > idx, the better.
>
>
> Fine.
>
>
> >
> >>> + i = 0;
> >>
> >> Do we need to bail out here?
> >>
> > Yes I guess we can simply return.
> >
> >>> + }
> >>> + virtqueue_fill(vq, elem, elem->len, i++);
> >>> + }
> >>> +
> >>> + virtqueue_flush(vq, i);
> >>> + event_notifier_set(&svq->svq_call);
> >>> +
> >>> + if (check_for_avail_queue && svq->next_guest_avail_elem) {
> >>> + /*
> >>> + * Avail ring was full when vhost_svq_flush was called, so
> >>> it's a
> >>> + * good moment to make more descriptors available if possible
> >>> + */
> >>> + vhost_handle_guest_kick(svq);
> >>
> >> Is there better to have a similar check as vhost_handle_guest_kick() did?
> >>
> >> if (elem->out_num + elem->in_num >
> >> vhost_svq_available_slots(svq)) {
> >>
> > It will be duplicated when we call vhost_handle_guest_kick, won't it?
>
>
> Right, I mis-read the code.
>
>
> >
> >>> + }
> >>> +
> >>> + vhost_svq_set_notification(svq, true);
> >>
> >> A mb() is needed here? Otherwise we may lost a call here (where
> >> vhost_svq_more_used() is run before vhost_svq_set_notification()).
> >>
> > I'm confused here then, I thought you said this is just a hint so
> > there was no need? [1]. I think the memory barrier is needed too.
>
>
> Yes, it's a hint but:
>
> 1) When we disable the notification, consider the notification disable
> is just a hint, device can still raise an interrupt, so the ordering is
> meaningless and a memory barrier is not necessary (the
> vhost_svq_set_notification(svq, false))
>
> 2) When we enable the notification, though it's a hint, the device can
> choose to implement it by enabling the interrupt, in this case, the
> notification enable should be done before checking the used. Otherwise,
> the checking of more used might be done before enable the notification:
>
> 1) driver check more used
> 2) device add more used but no notification
> 3) driver enable the notification then we lost a notification here
>
That was my understanding too. So the right way is to only add the
memory barrier in case 2), when setting the flag, right?
>
> >>> + } while (vhost_svq_more_used(svq));
> >>> +}
> >>> +
> >>> +/**
> >>> + * Forward used buffers.
> >>> + *
> >>> + * @n hdev call event notifier, the one that device set to notify svq.
> >>> + *
> >>> + * Note that we are not making any buffers available in the loop, there
> >>> is no
> >>> + * way that it runs more than virtqueue size times.
> >>> + */
> >>> static void vhost_svq_handle_call(EventNotifier *n)
> >>> {
> >>> VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue,
> >>> hdev_call);
> >>>
> >>> - if (unlikely(!event_notifier_test_and_clear(n))) {
> >>> - return;
> >>> - }
> >>> + /* Clear event notifier */
> >>> + event_notifier_test_and_clear(n);
> >>
> >> Any reason that we remove the above check?
> >>
> > This comes from the previous versions, where this made sure we missed
> > no used buffers in the process of switching to SVQ mode.
>
>
> I'm not sure I get here. Even if for the switching, it should be more
> safe the handle the flush unconditionally?
>
Yes, I also think it's better to forward and kick/call unconditionally.
Thanks!
> Thanks
>
>
> >
> > If we enable SVQ from the beginning I think we can rely on getting all
> > the device's used buffer notifications, so let me think a little bit
> > and I can move to check the eventfd.
> >
> >>> - event_notifier_set(&svq->svq_call);
> >>> + vhost_svq_flush(svq, true);
> >>> }
> >>>
> >>> /**
> >>> @@ -258,13 +551,38 @@ void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue
> >>> *svq, int svq_kick_fd)
> >>> * need to explicitely check for them.
> >>> */
> >>> event_notifier_init_fd(&svq->svq_kick, svq_kick_fd);
> >>> - event_notifier_set_handler(&svq->svq_kick, vhost_handle_guest_kick);
> >>> + event_notifier_set_handler(&svq->svq_kick,
> >>> + vhost_handle_guest_kick_notifier);
> >>>
> >>> if (!check_old || event_notifier_test_and_clear(&tmp)) {
> >>> event_notifier_set(&svq->hdev_kick);
> >>> }
> >>> }
> >>>
> >>> +/**
> >>> + * Start shadow virtqueue operation.
> >>> + *
> >>> + * @svq Shadow Virtqueue
> >>> + * @vdev VirtIO device
> >>> + * @vq Virtqueue to shadow
> >>> + */
> >>> +void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
> >>> + VirtQueue *vq)
> >>> +{
> >>> + svq->next_guest_avail_elem = NULL;
> >>> + svq->avail_idx_shadow = 0;
> >>> + svq->shadow_used_idx = 0;
> >>> + svq->last_used_idx = 0;
> >>> + svq->vdev = vdev;
> >>> + svq->vq = vq;
> >>> +
> >>> + memset(svq->vring.avail, 0, sizeof(*svq->vring.avail));
> >>> + memset(svq->vring.used, 0, sizeof(*svq->vring.avail));
> >>> + for (unsigned i = 0; i < svq->vring.num - 1; i++) {
> >>> + svq->vring.desc[i].next = cpu_to_le16(i + 1);
> >>> + }
> >>> +}
> >>> +
> >>> /**
> >>> * Stop shadow virtqueue operation.
> >>> * @svq Shadow Virtqueue
> >>> @@ -272,6 +590,28 @@ void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue
> >>> *svq, int svq_kick_fd)
> >>> void vhost_svq_stop(VhostShadowVirtqueue *svq)
> >>> {
> >>> event_notifier_set_handler(&svq->svq_kick, NULL);
> >>> + g_autofree VirtQueueElement *next_avail_elem = NULL;
> >>> +
> >>> + if (!svq->vq) {
> >>> + return;
> >>> + }
> >>> +
> >>> + /* Send all pending used descriptors to guest */
> >>> + vhost_svq_flush(svq, false);
> >>> +
> >>> + for (unsigned i = 0; i < svq->vring.num; ++i) {
> >>> + g_autofree VirtQueueElement *elem = NULL;
> >>> + elem = g_steal_pointer(&svq->ring_id_maps[i]);
> >>> + if (elem) {
> >>> + virtqueue_detach_element(svq->vq, elem, elem->len);
> >>> + }
> >>> + }
> >>> +
> >>> + next_avail_elem = g_steal_pointer(&svq->next_guest_avail_elem);
> >>> + if (next_avail_elem) {
> >>> + virtqueue_detach_element(svq->vq, next_avail_elem,
> >>> + next_avail_elem->len);
> >>> + }
> >>> }
> >>>
> >>> /**
> >>> @@ -316,7 +656,7 @@ VhostShadowVirtqueue *vhost_svq_new(uint16_t qsize)
> >>> 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->ring_id_maps = g_new0(VirtQueueElement *, qsize);
> >>> event_notifier_set_handler(&svq->hdev_call, vhost_svq_handle_call);
> >>> return g_steal_pointer(&svq);
> >>>
> >>> @@ -335,6 +675,7 @@ void vhost_svq_free(VhostShadowVirtqueue *vq)
> >>> event_notifier_cleanup(&vq->hdev_kick);
> >>> event_notifier_set_handler(&vq->hdev_call, NULL);
> >>> event_notifier_cleanup(&vq->hdev_call);
> >>> + g_free(vq->ring_id_maps);
> >>> qemu_vfree(vq->vring.desc);
> >>> qemu_vfree(vq->vring.used);
> >>> g_free(vq);
> >>> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> >>> index 53e14bafa0..0e5c00ed7e 100644
> >>> --- a/hw/virtio/vhost-vdpa.c
> >>> +++ b/hw/virtio/vhost-vdpa.c
> >>> @@ -752,9 +752,9 @@ static int vhost_vdpa_set_vring_call(struct vhost_dev
> >>> *dev,
> >>> * Note that this function does not rewind kick file descriptor if
> >>> cannot set
> >>> * call one.
> >>> */
> >>> -static bool vhost_vdpa_svq_setup(struct vhost_dev *dev,
> >>> - VhostShadowVirtqueue *svq,
> >>> - unsigned idx)
> >>> +static int vhost_vdpa_svq_set_fds(struct vhost_dev *dev,
> >>> + VhostShadowVirtqueue *svq,
> >>> + unsigned idx)
> >>> {
> >>> struct vhost_vring_file file = {
> >>> .index = dev->vq_index + idx,
> >>> @@ -767,7 +767,7 @@ static bool vhost_vdpa_svq_setup(struct vhost_dev
> >>> *dev,
> >>> r = vhost_vdpa_set_vring_dev_kick(dev, &file);
> >>> if (unlikely(r != 0)) {
> >>> error_report("Can't set device kick fd (%d)", -r);
> >>> - return false;
> >>> + return r;
> >>> }
> >>>
> >>> event_notifier = vhost_svq_get_svq_call_notifier(svq);
> >>> @@ -777,6 +777,99 @@ static bool vhost_vdpa_svq_setup(struct vhost_dev
> >>> *dev,
> >>> error_report("Can't set device call fd (%d)", -r);
> >>> }
> >>>
> >>> + return r;
> >>> +}
> >>> +
> >>> +/**
> >>> + * Unmap SVQ area in the device
> >>> + */
> >>> +static bool vhost_vdpa_svq_unmap_ring(struct vhost_vdpa *v, hwaddr iova,
> >>> + hwaddr size)
> >>> +{
> >>> + int r;
> >>> +
> >>> + size = ROUND_UP(size, qemu_real_host_page_size);
> >>> + r = vhost_vdpa_dma_unmap(v, iova, size);
> >>> + return r == 0;
> >>> +}
> >>> +
> >>> +static bool vhost_vdpa_svq_unmap_rings(struct vhost_dev *dev,
> >>> + const VhostShadowVirtqueue *svq)
> >>> +{
> >>> + struct vhost_vdpa *v = dev->opaque;
> >>> + struct vhost_vring_addr svq_addr;
> >>> + size_t device_size = vhost_svq_device_area_size(svq);
> >>> + size_t driver_size = vhost_svq_driver_area_size(svq);
> >>> + bool ok;
> >>> +
> >>> + vhost_svq_get_vring_addr(svq, &svq_addr);
> >>> +
> >>> + ok = vhost_vdpa_svq_unmap_ring(v, svq_addr.desc_user_addr,
> >>> driver_size);
> >>> + if (unlikely(!ok)) {
> >>> + return false;
> >>> + }
> >>> +
> >>> + return vhost_vdpa_svq_unmap_ring(v, svq_addr.used_user_addr,
> >>> device_size);
> >>> +}
> >>> +
> >>> +/**
> >>> + * Map shadow virtqueue rings in device
> >>> + *
> >>> + * @dev The vhost device
> >>> + * @svq The shadow virtqueue
> >>> + */
> >>> +static bool vhost_vdpa_svq_map_rings(struct vhost_dev *dev,
> >>> + const VhostShadowVirtqueue *svq)
> >>> +{
> >>> + struct vhost_vdpa *v = dev->opaque;
> >>> + struct vhost_vring_addr svq_addr;
> >>> + size_t device_size = vhost_svq_device_area_size(svq);
> >>> + size_t driver_size = vhost_svq_driver_area_size(svq);
> >>> + int r;
> >>> +
> >>> + vhost_svq_get_vring_addr(svq, &svq_addr);
> >>> +
> >>> + r = vhost_vdpa_dma_map(v, svq_addr.desc_user_addr, driver_size,
> >>> + (void *)svq_addr.desc_user_addr, true);
> >>> + if (unlikely(r != 0)) {
> >>> + return false;
> >>> + }
> >>> +
> >>> + r = vhost_vdpa_dma_map(v, svq_addr.used_user_addr, device_size,
> >>> + (void *)svq_addr.used_user_addr, false);
> >>
> >> Do we need unmap the driver area if we fail here?
> >>
> > Yes, this used to trust in unmap them at the disabling of SVQ. Now I
> > think we need to unmap as you say.
> >
> > Thanks!
> >
> > [1]
> > https://lists.linuxfoundation.org/pipermail/virtualization/2021-March/053322.html
> >
> >> Thanks
> >>
> >>
> >>> + return r == 0;
> >>> +}
> >>> +
> >>> +static bool vhost_vdpa_svq_setup(struct vhost_dev *dev,
> >>> + VhostShadowVirtqueue *svq,
> >>> + unsigned idx)
> >>> +{
> >>> + uint16_t vq_index = dev->vq_index + idx;
> >>> + struct vhost_vring_state s = {
> >>> + .index = vq_index,
> >>> + };
> >>> + int r;
> >>> + bool ok;
> >>> +
> >>> + r = vhost_vdpa_set_dev_vring_base(dev, &s);
> >>> + if (unlikely(r)) {
> >>> + error_report("Can't set vring base (%d)", r);
> >>> + return false;
> >>> + }
> >>> +
> >>> + s.num = vhost_svq_get_num(svq);
> >>> + r = vhost_vdpa_set_dev_vring_num(dev, &s);
> >>> + if (unlikely(r)) {
> >>> + error_report("Can't set vring num (%d)", r);
> >>> + return false;
> >>> + }
> >>> +
> >>> + ok = vhost_vdpa_svq_map_rings(dev, svq);
> >>> + if (unlikely(!ok)) {
> >>> + return false;
> >>> + }
> >>> +
> >>> + r = vhost_vdpa_svq_set_fds(dev, svq, idx);
> >>> return r == 0;
> >>> }
> >>>
> >>> @@ -788,14 +881,24 @@ static int vhost_vdpa_dev_start(struct vhost_dev
> >>> *dev, bool started)
> >>> if (started) {
> >>> vhost_vdpa_host_notifiers_init(dev);
> >>> for (unsigned i = 0; i < v->shadow_vqs->len; ++i) {
> >>> + VirtQueue *vq = virtio_get_queue(dev->vdev, dev->vq_index +
> >>> i);
> >>> VhostShadowVirtqueue *svq =
> >>> g_ptr_array_index(v->shadow_vqs, i);
> >>> bool ok = vhost_vdpa_svq_setup(dev, svq, i);
> >>> if (unlikely(!ok)) {
> >>> return -1;
> >>> }
> >>> + vhost_svq_start(svq, dev->vdev, vq);
> >>> }
> >>> vhost_vdpa_set_vring_ready(dev);
> >>> } else {
> >>> + for (unsigned i = 0; i < v->shadow_vqs->len; ++i) {
> >>> + VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs,
> >>> + i);
> >>> + bool ok = vhost_vdpa_svq_unmap_rings(dev, svq);
> >>> + if (unlikely(!ok)) {
> >>> + return -1;
> >>> + }
> >>> + }
> >>> vhost_vdpa_host_notifiers_uninit(dev, dev->nvqs);
> >>> }
> >>>
>