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Re: [PATCH v2 07/14] vhost: Shadow virtqueue buffers forwarding
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From: |
Eugenio Perez Martin |
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Subject: |
Re: [PATCH v2 07/14] vhost: Shadow virtqueue buffers forwarding |
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Date: |
Wed, 2 Mar 2022 19:23:25 +0100 |
On Mon, Feb 28, 2022 at 6:39 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2022/2/27 下午9:41, 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 | 29 +++
> > hw/virtio/vhost-shadow-virtqueue.c | 360 ++++++++++++++++++++++++++++-
> > hw/virtio/vhost-vdpa.c | 165 ++++++++++++-
> > 3 files changed, 542 insertions(+), 12 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-shadow-virtqueue.h
> > b/hw/virtio/vhost-shadow-virtqueue.h
> > index 3bbea77082..04c67685fd 100644
> > --- a/hw/virtio/vhost-shadow-virtqueue.h
> > +++ b/hw/virtio/vhost-shadow-virtqueue.h
> > @@ -36,6 +36,33 @@ typedef struct VhostShadowVirtqueue {
> >
> > /* Guest's call notifier, where the SVQ calls guest. */
> > EventNotifier svq_call;
> > +
> > + /* Virtio queue shadowing */
> > + VirtQueue *vq;
> > +
> > + /* Virtio device */
> > + VirtIODevice *vdev;
> > +
> > + /* Map for use the guest's descriptors */
> > + VirtQueueElement **ring_id_maps;
> > +
> > + /* Next VirtQueue element that guest made available */
> > + VirtQueueElement *next_guest_avail_elem;
> > +
> > + /* Next head to expose to the device */
> > + uint16_t avail_idx_shadow;
> > +
> > + /* Next free descriptor */
> > + uint16_t free_head;
> > +
> > + /* Last seen used idx */
> > + uint16_t shadow_used_idx;
>
>
> I suggest to have a consistent name for avail and used instead of using
> one "shadow" as prefix and other as suffix
>
Right, I'll fix that.
>
> > +
> > + /* Next head to consume from the device */
> > + uint16_t last_used_idx;
> > +
> > + /* Cache for the exposed notification flag */
> > + bool notification;
> > } VhostShadowVirtqueue;
> >
> > bool vhost_svq_valid_features(uint64_t *features);
> > @@ -47,6 +74,8 @@ void vhost_svq_get_vring_addr(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(void);
> > diff --git a/hw/virtio/vhost-shadow-virtqueue.c
> > b/hw/virtio/vhost-shadow-virtqueue.c
> > index 2150e2b071..a38d313755 100644
> > --- a/hw/virtio/vhost-shadow-virtqueue.c
> > +++ b/hw/virtio/vhost-shadow-virtqueue.c
> > @@ -12,6 +12,7 @@
> >
> > #include "qemu/error-report.h"
> > #include "qemu/main-loop.h"
> > +#include "qemu/log.h"
> > #include "linux-headers/linux/vhost.h"
> >
> > /**
> > @@ -53,22 +54,309 @@ bool vhost_svq_valid_features(uint64_t *features)
> > return r;
> > }
> >
> > -/** Forward guest notifications */
> > -static void vhost_handle_guest_kick(EventNotifier *n)
> > +/**
> > + * Number of descriptors that the SVQ can make available from the guest.
> > + *
> > + * @svq The svq
>
>
> Btw, I notice most of function there will be a colon in the middle of
> the parameter and it's documentation. Maybe we should follow that.
>
Sure, it seems I picked the uncommon template without realizing.
>
> > + */
> > +static uint16_t vhost_svq_available_slots(const VhostShadowVirtqueue *svq)
> > +{
> > + 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 (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;
> > + /* Make sure the flag is written before the read of used_idx */
> > + smp_mb();
>
>
> So the comment assumes that a reading of used_idx will come. This makes
> me wonder if we can simply split this function as:
>
> vhost_svq_disable_notification() and vhost_svq_enable_notification()
>
> and in the vhost_svq_enable_notification, we simply return
> vhost_svq_more_used() after smp_mb().
>
> (Not a must but just feel it might be more clear)
>
Ok, like kernel's virtio_ring.c I suppose.
>
> > + }
> > +}
> > +
> > +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 bool vhost_svq_add_split(VhostShadowVirtqueue *svq,
> > + VirtQueueElement *elem,
> > + unsigned *head)
> > +{
> > + unsigned avail_idx;
> > + vring_avail_t *avail = svq->vring.avail;
> > +
> > + *head = svq->free_head;
> > +
> > + /* We need some descriptors here */
> > + if (unlikely(!elem->out_num && !elem->in_num)) {
> > + qemu_log_mask(LOG_GUEST_ERROR,
> > + "Guest provided element with no descriptors");
> > + return false;
> > + }
> > +
> > + 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);
>
>
> I wonder instead of passing in/out separately and using the hint like
> more_descs, is it better to simply pass the elem to
> vhost_vrign_write_descs() then we know which one is the last that
> doesn't depend on more_descs.
>
I'm not sure I follow this.
The purpose of vhost_vring_write_descs is to abstract the writing of a
batch of descriptors, its chaining, etc. It accepts the write
parameter just for the write flag. If we make elem as a parameter, we
would need to duplicate that for loop for read and for write
descriptors, isn't it?
To duplicate the for loop is the way it is done in the kernel, but I
actually think the kernel could benefit from abstracting both in the
same function too. Please let me know if you think otherwise or I've
missed your point.
>
> > +
> > + /*
> > + * Put the entry in the 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 the avail index after write the descriptor */
> > + smp_wmb();
> > + avail->idx = cpu_to_le16(svq->avail_idx_shadow);
> > +
> > + return true;
> > +}
> > +
> > +static bool vhost_svq_add(VhostShadowVirtqueue *svq, VirtQueueElement
> > *elem)
> > +{
> > + unsigned qemu_head;
> > + bool ok = vhost_svq_add_split(svq, elem, &qemu_head);
> > + if (unlikely(!ok)) {
> > + return false;
> > + }
> > +
> > + svq->ring_id_maps[qemu_head] = elem;
> > + return true;
> > +}
> > +
> > +static void vhost_svq_kick(VhostShadowVirtqueue *svq)
> > +{
> > + /*
> > + * We need to expose the available array entries before checking the
> > used
> > + * flags
> > + */
> > + smp_mb();
> > + if (svq->vring.used->flags & VRING_USED_F_NO_NOTIFY) {
> > + return;
> > + }
> > +
> > + event_notifier_set(&svq->hdev_kick);
> > +}
> > +
> > +/**
> > + * 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 contiguous buffer, but it may not be contiguous in
> > + * qemu vaddr.
> > + *
> > + * If that happens, guest's kick notifications will be disabled until the
> > + * device uses some buffers.
> > + */
> > +static void vhost_handle_guest_kick(VhostShadowVirtqueue *svq)
> > +{
> > + /* Clear event notifier */
> > + event_notifier_test_and_clear(&svq->svq_kick);
> > +
> > + /* Forward to the device as many available buffers as possible */
> > + do {
> > + virtio_queue_set_notification(svq->vq, false);
> > +
> > + while (true) {
> > + VirtQueueElement *elem;
> > + bool ok;
> > +
> > + 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 happens, 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;
> > + }
> > +
> > + ok = vhost_svq_add(svq, elem);
> > + if (unlikely(!ok)) {
> > + /* VQ is broken, just return and ignore any other kicks */
> > + return;
> > + }
> > + 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);
> > event_notifier_test_and_clear(n);
> > - event_notifier_set(&svq->hdev_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;
> > }
> >
> > -/* Forward vhost notifications */
> > +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)) {
> > + qemu_log_mask(LOG_GUEST_ERROR, "Device %s says index %u is used",
> > + svq->vdev->name, used_elem.id);
> > + return NULL;
> > + }
> > +
> > + if (unlikely(!svq->ring_id_maps[used_elem.id])) {
> > + qemu_log_mask(LOG_GUEST_ERROR,
> > + "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;
>
>
> It looks to me we'd better not modify the elem here, otherwise we may
> leak mapping during virtqueue_unmap_sg()?
>
Right, it's better to track it separately.
>
> > + 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;
> > +
> > + /* Forward as many used buffers as possible. */
> > + 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)) {
> > + qemu_log_mask(LOG_GUEST_ERROR,
> > + "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);
> > + 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);
> > + }
> > +
> > + vhost_svq_set_notification(svq, true);
> > + } 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);
> > event_notifier_test_and_clear(n);
> > - event_notifier_set(&svq->svq_call);
> > + vhost_svq_flush(svq, true);
> > }
> >
> > /**
> > @@ -149,7 +437,41 @@ void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue
> > *svq, int svq_kick_fd)
> > if (poll_start) {
> > event_notifier_init_fd(svq_kick, svq_kick_fd);
> > event_notifier_set(svq_kick);
> > - event_notifier_set_handler(svq_kick, vhost_handle_guest_kick);
> > + event_notifier_set_handler(svq_kick,
> > vhost_handle_guest_kick_notifier);
> > + }
> > +}
> > +
> > +/**
> > + * Start the shadow virtqueue operation.
> > + *
> > + * @svq Shadow Virtqueue
> > + * @vdev VirtIO device
> > + * @vq Virtqueue to shadow
> > + */
> > +void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
> > + VirtQueue *vq)
> > +{
> > + size_t desc_size, driver_size, device_size;
> > +
> > + 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;
> > +
> > + svq->vring.num = virtio_queue_get_num(vdev,
> > virtio_get_queue_index(vq));
> > + driver_size = vhost_svq_driver_area_size(svq);
> > + device_size = vhost_svq_device_area_size(svq);
> > + svq->vring.desc = qemu_memalign(qemu_real_host_page_size, driver_size);
> > + desc_size = sizeof(vring_desc_t) * svq->vring.num;
> > + svq->vring.avail = (void *)((char *)svq->vring.desc + desc_size);
> > + 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 *, svq->vring.num);
> > + for (unsigned i = 0; i < svq->vring.num - 1; i++) {
> > + svq->vring.desc[i].next = cpu_to_le16(i + 1);
> > }
> > }
> >
> > @@ -160,6 +482,32 @@ 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);
> > + }
> > + svq->vq = NULL;
> > + g_free(svq->ring_id_maps);
> > + qemu_vfree(svq->vring.desc);
> > + qemu_vfree(svq->vring.used);
> > }
> >
> > /**
> > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > index b2c4e92fcf..435b9c2e9e 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -803,10 +803,10 @@ static int vhost_vdpa_set_vring_dev_addr(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,
> > - Error **errp)
> > +static int vhost_vdpa_svq_set_fds(struct vhost_dev *dev,
> > + VhostShadowVirtqueue *svq,
> > + unsigned idx,
> > + Error **errp)
> > {
> > struct vhost_vring_file file = {
> > .index = dev->vq_index + idx,
> > @@ -818,7 +818,7 @@ static bool vhost_vdpa_svq_setup(struct vhost_dev *dev,
> > r = vhost_vdpa_set_vring_dev_kick(dev, &file);
> > if (unlikely(r != 0)) {
> > error_setg_errno(errp, -r, "Can't set device kick fd");
> > - return false;
> > + return r;
> > }
> >
> > event_notifier = &svq->hdev_call;
> > @@ -828,6 +828,119 @@ static bool vhost_vdpa_svq_setup(struct vhost_dev
> > *dev,
> > error_setg_errno(errp, -r, "Can't set device call fd");
> > }
> >
> > + return r;
> > +}
> > +
> > +/**
> > + * Unmap a 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
> > + * @addr Assigned IOVA addresses
> > + * @errp Error pointer
> > + */
> > +static bool vhost_vdpa_svq_map_rings(struct vhost_dev *dev,
> > + const VhostShadowVirtqueue *svq,
> > + struct vhost_vring_addr *addr,
> > + Error **errp)
> > +{
> > + struct vhost_vdpa *v = dev->opaque;
> > + size_t device_size = vhost_svq_device_area_size(svq);
> > + size_t driver_size = vhost_svq_driver_area_size(svq);
> > + int r;
> > +
> > + ERRP_GUARD();
> > + vhost_svq_get_vring_addr(svq, addr);
> > +
> > + r = vhost_vdpa_dma_map(v, addr->desc_user_addr, driver_size,
> > + (void *)addr->desc_user_addr, true);
> > + if (unlikely(r != 0)) {
> > + error_setg_errno(errp, -r, "Cannot create vq driver region: ");
> > + return false;
> > + }
> > +
> > + r = vhost_vdpa_dma_map(v, addr->used_user_addr, device_size,
> > + (void *)addr->used_user_addr, false);
> > + if (unlikely(r != 0)) {
> > + error_setg_errno(errp, -r, "Cannot create vq device region: ");
> > + }
> > +
> > + return r == 0;
> > +}
> > +
> > +static bool vhost_vdpa_svq_setup(struct vhost_dev *dev,
> > + VhostShadowVirtqueue *svq,
> > + unsigned idx,
> > + Error **errp)
> > +{
> > + uint16_t vq_index = dev->vq_index + idx;
> > + struct vhost_vring_state s = {
> > + .index = vq_index,
> > + };
> > + int r;
> > +
> > + r = vhost_vdpa_set_dev_vring_base(dev, &s);
> > + if (unlikely(r)) {
> > + error_setg_errno(errp, -r, "Cannot set vring base");
> > + return false;
> > + }
> > +
> > + r = vhost_vdpa_svq_set_fds(dev, svq, idx, errp);
> > + return r == 0;
> > +}
> > +
> > +static bool vhost_vdpa_svq_set_addr(struct vhost_dev *dev, unsigned idx,
> > + VhostShadowVirtqueue *svq,
> > + Error **errp)
> > +{
> > + struct vhost_vring_addr addr = {
> > + .index = idx,
> > + };
> > + int r;
> > +
> > + bool ok = vhost_vdpa_svq_map_rings(dev, svq, &addr, errp);
> > + if (unlikely(!ok)) {
> > + return false;
> > + }
> > +
> > + /* Override vring GPA set by vhost subsystem */
> > + r = vhost_vdpa_set_vring_dev_addr(dev, &addr);
> > + if (unlikely(r != 0)) {
> > + error_setg_errno(errp, -r, "Cannot set device address");
> > + }
> > +
> > return r == 0;
> > }
> >
> > @@ -842,10 +955,46 @@ static bool vhost_vdpa_svqs_start(struct vhost_dev
> > *dev)
> > }
> >
> > for (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, &err);
> > if (unlikely(!ok)) {
> > - error_reportf_err(err, "Cannot setup SVQ %u: ", i);
> > + goto err;
> > + }
> > + vhost_svq_start(svq, dev->vdev, vq);
> > + ok = vhost_vdpa_svq_set_addr(dev, i, svq, &err);
> > + if (unlikely(!ok)) {
> > + vhost_svq_stop(svq);
> > + goto err;
>
>
> Nit: let's introduce a new error label for this?
>
I'm fine with that, but this unwinding index i, calling vhost_svq_stop
on svqs[i]. The code at err label works on j < i.
So there would be something like:
err_mapping:
/* Unwind current starting SVQ */
vhost_svq_stop(svqs[i]);
err:
for j in [0, i) {
vhost_svq_stop(svqs[j]);
unmap_rings(svqs[j]);
}
Repeating the vhost_svq_stop calling on different indexes.
>
> > + }
> > + }
> > +
> > + return true;
> > +
> > +err:
> > + error_reportf_err(err, "Cannot setup SVQ %u: ", i);
> > + for (unsigned j = 0; j < i; ++j) {
> > + VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs, j);
> > + vhost_vdpa_svq_unmap_rings(dev, svq);
>
>
> I wonder if it's better to move the vhost_vdpa_svq_map_rings() out of
> vhost_vdpa_svq_set_addr(). (This function seems to be the only user for
> that). This will makes the error handling logic more clear.
>
Yes, I'll move it out.
Thanks!
> Thanks
>
>
> > + vhost_svq_stop(svq);
> > + }
> > +
> > + return false;
> > +}
> > +
> > +static bool vhost_vdpa_svqs_stop(struct vhost_dev *dev)
> > +{
> > + struct vhost_vdpa *v = dev->opaque;
> > +
> > + if (!v->shadow_vqs) {
> > + return true;
> > + }
> > +
> > + 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 false;
> > }
> > }
> > @@ -867,6 +1016,10 @@ static int vhost_vdpa_dev_start(struct vhost_dev
> > *dev, bool started)
> > }
> > vhost_vdpa_set_vring_ready(dev);
> > } else {
> > + ok = vhost_vdpa_svqs_stop(dev);
> > + if (unlikely(!ok)) {
> > + return -1;
> > + }
> > vhost_vdpa_host_notifiers_uninit(dev, dev->nvqs);
> > }
> >
>
- Re: [PATCH v2 07/14] vhost: Shadow virtqueue buffers forwarding,
Eugenio Perez Martin <=