Re: [Qemu-devel] [PATCH RFC 07/11] dataplane: allow virtio-1 devices

[Greg Kurz <gkurz@linux.vnet.ibm.com>]

On Tue,  7 Oct 2014 16:40:03 +0200
Cornelia Huck <cornelia.huck@de.ibm.com> wrote:

> Handle endianness conversion for virtio-1 virtqueues correctly.
> 
> Note that dataplane now needs to be built per-target.
> 

It also affects hw/virtio/virtio-pci.c:

In file included from include/hw/virtio/dataplane/vring.h:23:0,
                 from include/hw/virtio/virtio-scsi.h:21,
                 from hw/virtio/virtio-pci.c:24:
include/hw/virtio/virtio-access.h: In function ‘virtio_access_is_big_endian’:
include/hw/virtio/virtio-access.h:28:15: error: attempt to use poisoned "TARGET_WORDS_BIGENDIAN"
 #elif defined(TARGET_WORDS_BIGENDIAN)
               ^

FWIW when I added endian ambivalent support to virtio, I remember *some people*
getting angry at the idea of turning common code into per-target... :)

See comment below.

> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
>  hw/block/dataplane/virtio-blk.c     |    3 +-
>  hw/scsi/virtio-scsi-dataplane.c     |    2 +-
>  hw/virtio/Makefile.objs             |    2 +-
>  hw/virtio/dataplane/Makefile.objs   |    2 +-
>  hw/virtio/dataplane/vring.c         |   85 +++++++++++++++++++----------------
>  include/hw/virtio/dataplane/vring.h |   64 ++++++++++++++++++++++++--
>  6 files changed, 113 insertions(+), 45 deletions(-)
> 
> diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
> index 5458f9d..eb45a3d 100644
> --- a/hw/block/dataplane/virtio-blk.c
> +++ b/hw/block/dataplane/virtio-blk.c
> @@ -16,6 +16,7 @@
>  #include "qemu/iov.h"
>  #include "qemu/thread.h"
>  #include "qemu/error-report.h"
> +#include "hw/virtio/virtio-access.h"
>  #include "hw/virtio/dataplane/vring.h"
>  #include "block/block.h"
>  #include "hw/virtio/virtio-blk.h"
> @@ -75,7 +76,7 @@ static void complete_request_vring(VirtIOBlockReq *req, unsigned char status)
>      VirtIOBlockDataPlane *s = req->dev->dataplane;
>      stb_p(&req->in->status, status);
> 
> -    vring_push(&req->dev->dataplane->vring, &req->elem,
> +    vring_push(s->vdev, &req->dev->dataplane->vring, &req->elem,
>                 req->qiov.size + sizeof(*req->in));
> 
>      /* Suppress notification to guest by BH and its scheduled
> diff --git a/hw/scsi/virtio-scsi-dataplane.c b/hw/scsi/virtio-scsi-dataplane.c
> index b778e05..3e2b706 100644
> --- a/hw/scsi/virtio-scsi-dataplane.c
> +++ b/hw/scsi/virtio-scsi-dataplane.c
> @@ -81,7 +81,7 @@ VirtIOSCSIReq *virtio_scsi_pop_req_vring(VirtIOSCSI *s,
> 
>  void virtio_scsi_vring_push_notify(VirtIOSCSIReq *req)
>  {
> -    vring_push(&req->vring->vring, &req->elem,
> +    vring_push((VirtIODevice *)req->dev, &req->vring->vring, &req->elem,
>                 req->qsgl.size + req->resp_iov.size);
>      event_notifier_set(&req->vring->guest_notifier);
>  }
> diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
> index d21c397..19b224a 100644
> --- a/hw/virtio/Makefile.objs
> +++ b/hw/virtio/Makefile.objs
> @@ -2,7 +2,7 @@ common-obj-y += virtio-rng.o
>  common-obj-$(CONFIG_VIRTIO_PCI) += virtio-pci.o
>  common-obj-y += virtio-bus.o
>  common-obj-y += virtio-mmio.o
> -common-obj-$(CONFIG_VIRTIO) += dataplane/
> +obj-$(CONFIG_VIRTIO) += dataplane/
> 
>  obj-y += virtio.o virtio-balloon.o 
>  obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
> diff --git a/hw/virtio/dataplane/Makefile.objs b/hw/virtio/dataplane/Makefile.objs
> index 9a8cfc0..753a9ca 100644
> --- a/hw/virtio/dataplane/Makefile.objs
> +++ b/hw/virtio/dataplane/Makefile.objs
> @@ -1 +1 @@
> -common-obj-y += vring.o
> +obj-y += vring.o
> diff --git a/hw/virtio/dataplane/vring.c b/hw/virtio/dataplane/vring.c
> index b84957f..4624521 100644
> --- a/hw/virtio/dataplane/vring.c
> +++ b/hw/virtio/dataplane/vring.c
> @@ -18,6 +18,7 @@
>  #include "hw/hw.h"
>  #include "exec/memory.h"
>  #include "exec/address-spaces.h"
> +#include "hw/virtio/virtio-access.h"
>  #include "hw/virtio/dataplane/vring.h"
>  #include "qemu/error-report.h"
> 
> @@ -83,7 +84,7 @@ bool vring_setup(Vring *vring, VirtIODevice *vdev, int n)
>      vring_init(&vring->vr, virtio_queue_get_num(vdev, n), vring_ptr, 4096);
> 
>      vring->last_avail_idx = virtio_queue_get_last_avail_idx(vdev, n);
> -    vring->last_used_idx = vring->vr.used->idx;
> +    vring->last_used_idx = vring_get_used_idx(vdev, vring);
>      vring->signalled_used = 0;
>      vring->signalled_used_valid = false;
> 
> @@ -104,7 +105,7 @@ void vring_teardown(Vring *vring, VirtIODevice *vdev, int n)
>  void vring_disable_notification(VirtIODevice *vdev, Vring *vring)
>  {
>      if (!(vdev->guest_features[0] & (1 << VIRTIO_RING_F_EVENT_IDX))) {
> -        vring->vr.used->flags |= VRING_USED_F_NO_NOTIFY;
> +        vring_set_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
>      }
>  }
> 
> @@ -117,10 +118,10 @@ bool vring_enable_notification(VirtIODevice *vdev, Vring *vring)
>      if (vdev->guest_features[0] & (1 << VIRTIO_RING_F_EVENT_IDX)) {
>          vring_avail_event(&vring->vr) = vring->vr.avail->idx;
>      } else {
> -        vring->vr.used->flags &= ~VRING_USED_F_NO_NOTIFY;
> +        vring_clear_used_flags(vdev, vring, VRING_USED_F_NO_NOTIFY);
>      }
>      smp_mb(); /* ensure update is seen before reading avail_idx */
> -    return !vring_more_avail(vring);
> +    return !vring_more_avail(vdev, vring);
>  }
> 
>  /* This is stolen from linux/drivers/vhost/vhost.c:vhost_notify() */
> @@ -134,12 +135,13 @@ bool vring_should_notify(VirtIODevice *vdev, Vring *vring)
>      smp_mb();
> 
>      if ((vdev->guest_features[0] & VIRTIO_F_NOTIFY_ON_EMPTY) &&
> -        unlikely(vring->vr.avail->idx == vring->last_avail_idx)) {
> +        unlikely(!vring_more_avail(vdev, vring))) {
>          return true;
>      }
> 
>      if (!(vdev->guest_features[0] & VIRTIO_RING_F_EVENT_IDX)) {
> -        return !(vring->vr.avail->flags & VRING_AVAIL_F_NO_INTERRUPT);
> +        return !(vring_get_avail_flags(vdev, vring) &
> +                 VRING_AVAIL_F_NO_INTERRUPT);
>      }
>      old = vring->signalled_used;
>      v = vring->signalled_used_valid;
> @@ -154,15 +156,18 @@ bool vring_should_notify(VirtIODevice *vdev, Vring *vring)
>  }
> 
> 
> -static int get_desc(Vring *vring, VirtQueueElement *elem,
> +static int get_desc(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem,
>                      struct vring_desc *desc)
>  {
>      unsigned *num;
>      struct iovec *iov;
>      hwaddr *addr;
>      MemoryRegion *mr;
> +    int is_write = virtio_tswap16(vdev, desc->flags) & VRING_DESC_F_WRITE;
> +    uint32_t len = virtio_tswap32(vdev, desc->len);
> +    uint64_t desc_addr = virtio_tswap64(vdev, desc->addr);
> 
> -    if (desc->flags & VRING_DESC_F_WRITE) {
> +    if (is_write) {
>          num = &elem->in_num;
>          iov = &elem->in_sg[*num];
>          addr = &elem->in_addr[*num];
> @@ -186,44 +191,45 @@ static int get_desc(Vring *vring, VirtQueueElement *elem,
>      }
> 
>      /* TODO handle non-contiguous memory across region boundaries */
> -    iov->iov_base = vring_map(&mr, desc->addr, desc->len,
> -                              desc->flags & VRING_DESC_F_WRITE);
> +    iov->iov_base = vring_map(&mr, desc_addr, len, is_write);
>      if (!iov->iov_base) {
>          error_report("Failed to map descriptor addr %#" PRIx64 " len %u",
> -                     (uint64_t)desc->addr, desc->len);
> +                     (uint64_t)desc_addr, len);
>          return -EFAULT;
>      }
> 
>      /* The MemoryRegion is looked up again and unref'ed later, leave the
>       * ref in place.  */
> -    iov->iov_len = desc->len;
> -    *addr = desc->addr;
> +    iov->iov_len = len;
> +    *addr = desc_addr;
>      *num += 1;
>      return 0;
>  }
> 
>  /* This is stolen from linux/drivers/vhost/vhost.c. */
> -static int get_indirect(Vring *vring, VirtQueueElement *elem,
> -                        struct vring_desc *indirect)
> +static int get_indirect(VirtIODevice *vdev, Vring *vring,
> +                        VirtQueueElement *elem, struct vring_desc *indirect)
>  {
>      struct vring_desc desc;
>      unsigned int i = 0, count, found = 0;
>      int ret;
> +    uint32_t len = virtio_tswap32(vdev, indirect->len);
> +    uint64_t addr = virtio_tswap64(vdev, indirect->addr);
> 
>      /* Sanity check */
> -    if (unlikely(indirect->len % sizeof(desc))) {
> +    if (unlikely(len % sizeof(desc))) {
>          error_report("Invalid length in indirect descriptor: "
>                       "len %#x not multiple of %#zx",
> -                     indirect->len, sizeof(desc));
> +                     len, sizeof(desc));
>          vring->broken = true;
>          return -EFAULT;
>      }
> 
> -    count = indirect->len / sizeof(desc);
> +    count = len / sizeof(desc);
>      /* Buffers are chained via a 16 bit next field, so
>       * we can have at most 2^16 of these. */
>      if (unlikely(count > USHRT_MAX + 1)) {
> -        error_report("Indirect buffer length too big: %d", indirect->len);
> +        error_report("Indirect buffer length too big: %d", len);
>          vring->broken = true;
>          return -EFAULT;
>      }
> @@ -234,12 +240,12 @@ static int get_indirect(Vring *vring, VirtQueueElement *elem,
> 
>          /* Translate indirect descriptor */
>          desc_ptr = vring_map(&mr,
> -                             indirect->addr + found * sizeof(desc),
> +                             addr + found * sizeof(desc),
>                               sizeof(desc), false);
>          if (!desc_ptr) {
>              error_report("Failed to map indirect descriptor "
>                           "addr %#" PRIx64 " len %zu",
> -                         (uint64_t)indirect->addr + found * sizeof(desc),
> +                         (uint64_t)addr + found * sizeof(desc),
>                           sizeof(desc));
>              vring->broken = true;
>              return -EFAULT;
> @@ -257,19 +263,20 @@ static int get_indirect(Vring *vring, VirtQueueElement *elem,
>              return -EFAULT;
>          }
> 
> -        if (unlikely(desc.flags & VRING_DESC_F_INDIRECT)) {
> +        if (unlikely(virtio_tswap16(vdev, desc.flags)
> +                     & VRING_DESC_F_INDIRECT)) {
>              error_report("Nested indirect descriptor");
>              vring->broken = true;
>              return -EFAULT;
>          }
> 
> -        ret = get_desc(vring, elem, &desc);
> +        ret = get_desc(vdev, vring, elem, &desc);
>          if (ret < 0) {
>              vring->broken |= (ret == -EFAULT);
>              return ret;
>          }
> -        i = desc.next;
> -    } while (desc.flags & VRING_DESC_F_NEXT);
> +        i = virtio_tswap16(vdev, desc.next);
> +    } while (virtio_tswap16(vdev, desc.flags) & VRING_DESC_F_NEXT);
>      return 0;
>  }
> 
> @@ -320,7 +327,7 @@ int vring_pop(VirtIODevice *vdev, Vring *vring,
> 
>      /* Check it isn't doing very strange things with descriptor numbers. */
>      last_avail_idx = vring->last_avail_idx;
> -    avail_idx = vring->vr.avail->idx;
> +    avail_idx = vring_get_avail_idx(vdev, vring);
>      barrier(); /* load indices now and not again later */
> 
>      if (unlikely((uint16_t)(avail_idx - last_avail_idx) > num)) {
> @@ -341,7 +348,7 @@ int vring_pop(VirtIODevice *vdev, Vring *vring,
> 
>      /* Grab the next descriptor number they're advertising, and increment
>       * the index we've seen. */
> -    head = vring->vr.avail->ring[last_avail_idx % num];
> +    head = vring_get_avail_ring(vdev, vring, last_avail_idx % num);
> 
>      elem->index = head;
> 
> @@ -374,21 +381,21 @@ int vring_pop(VirtIODevice *vdev, Vring *vring,
>          /* Ensure descriptor is loaded before accessing fields */
>          barrier();
> 
> -        if (desc.flags & VRING_DESC_F_INDIRECT) {
> -            ret = get_indirect(vring, elem, &desc);
> +        if (virtio_tswap16(vdev, desc.flags) & VRING_DESC_F_INDIRECT) {
> +            ret = get_indirect(vdev, vring, elem, &desc);
>              if (ret < 0) {
>                  goto out;
>              }
>              continue;
>          }
> 
> -        ret = get_desc(vring, elem, &desc);
> +        ret = get_desc(vdev, vring, elem, &desc);
>          if (ret < 0) {
>              goto out;
>          }
> 
> -        i = desc.next;
> -    } while (desc.flags & VRING_DESC_F_NEXT);
> +        i = virtio_tswap16(vdev, desc.next);
> +    } while (virtio_tswap16(vdev, desc.flags) & VRING_DESC_F_NEXT);
> 
>      /* On success, increment avail index. */
>      vring->last_avail_idx++;
> @@ -407,9 +414,9 @@ out:
>   *
>   * Stolen from linux/drivers/vhost/vhost.c.
>   */
> -void vring_push(Vring *vring, VirtQueueElement *elem, int len)
> +void vring_push(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem,
> +                int len)
>  {
> -    struct vring_used_elem *used;
>      unsigned int head = elem->index;
>      uint16_t new;
> 
> @@ -422,14 +429,16 @@ void vring_push(Vring *vring, VirtQueueElement *elem, int len)
> 
>      /* The virtqueue contains a ring of used buffers.  Get a pointer to the
>       * next entry in that used ring. */
> -    used = &vring->vr.used->ring[vring->last_used_idx % vring->vr.num];
> -    used->id = head;
> -    used->len = len;
> +    vring_set_used_ring_id(vdev, vring, vring->last_used_idx % vring->vr.num,
> +                           head);
> +    vring_set_used_ring_len(vdev, vring, vring->last_used_idx % vring->vr.num,
> +                            len);
> 
>      /* Make sure buffer is written before we update index. */
>      smp_wmb();
> 
> -    new = vring->vr.used->idx = ++vring->last_used_idx;
> +    new = ++vring->last_used_idx;
> +    vring_set_used_idx(vdev, vring, new);
>      if (unlikely((int16_t)(new - vring->signalled_used) < (uint16_t)1)) {
>          vring->signalled_used_valid = false;
>      }
> diff --git a/include/hw/virtio/dataplane/vring.h b/include/hw/virtio/dataplane/vring.h
> index d3e086a..fde15f3 100644
> --- a/ 
> +++ b/include/hw/virtio/dataplane/vring.h
> @@ -20,6 +20,7 @@
>  #include "qemu-common.h"
>  #include "hw/virtio/virtio_ring.h"
>  #include "hw/virtio/virtio.h"
> +#include "hw/virtio/virtio-access.h"
> 

Since the following commit:

commit 244e2898b7a7735b3da114c120abe206af56a167
Author: Fam Zheng <famz@redhat.com>
Date:   Wed Sep 24 15:21:41 2014 +0800

    virtio-scsi: Add VirtIOSCSIVring in VirtIOSCSIReq

The include/hw/virtio/dataplane/vring.h header is indirectly included
by hw/virtio/virtio-pci.c. Why don't you move all this target dependent
helpers to another header ?

Cheers.

--
Greg

>  typedef struct {
>      MemoryRegion *mr;               /* memory region containing the vring */
> @@ -31,15 +32,71 @@ typedef struct {
>      bool broken;                    /* was there a fatal error? */
>  } Vring;
> 
> +static inline uint16_t vring_get_used_idx(VirtIODevice *vdev, Vring *vring)
> +{
> +    return virtio_tswap16(vdev, vring->vr.used->idx);
> +}
> +
> +static inline void vring_set_used_idx(VirtIODevice *vdev, Vring *vring,
> +                                      uint16_t idx)
> +{
> +    vring->vr.used->idx = virtio_tswap16(vdev, idx);
> +}
> +
> +static inline uint16_t vring_get_avail_idx(VirtIODevice *vdev, Vring *vring)
> +{
> +    return virtio_tswap16(vdev, vring->vr.avail->idx);
> +}
> +
> +static inline uint16_t vring_get_avail_ring(VirtIODevice *vdev, Vring *vring,
> +                                            int i)
> +{
> +    return virtio_tswap16(vdev, vring->vr.avail->ring[i]);
> +}
> +
> +static inline void vring_set_used_ring_id(VirtIODevice *vdev, Vring *vring,
> +                                          int i, uint32_t id)
> +{
> +    vring->vr.used->ring[i].id = virtio_tswap32(vdev, id);
> +}
> +
> +static inline void vring_set_used_ring_len(VirtIODevice *vdev, Vring *vring,
> +                                          int i, uint32_t len)
> +{
> +    vring->vr.used->ring[i].len = virtio_tswap32(vdev, len);
> +}
> +
> +static inline uint16_t vring_get_used_flags(VirtIODevice *vdev, Vring *vring)
> +{
> +    return virtio_tswap16(vdev, vring->vr.used->flags);
> +}
> +
> +static inline uint16_t vring_get_avail_flags(VirtIODevice *vdev, Vring *vring)
> +{
> +    return virtio_tswap16(vdev, vring->vr.avail->flags);
> +}
> +
> +static inline void vring_set_used_flags(VirtIODevice *vdev, Vring *vring,
> +                                        uint16_t flags)
> +{
> +    vring->vr.used->flags |= virtio_tswap16(vdev, flags);
> +}
> +
> +static inline void vring_clear_used_flags(VirtIODevice *vdev, Vring *vring,
> +                                          uint16_t flags)
> +{
> +    vring->vr.used->flags &= virtio_tswap16(vdev, ~flags);
> +}
> +
>  static inline unsigned int vring_get_num(Vring *vring)
>  {
>      return vring->vr.num;
>  }
> 
>  /* Are there more descriptors available? */
> -static inline bool vring_more_avail(Vring *vring)
> +static inline bool vring_more_avail(VirtIODevice *vdev, Vring *vring)
>  {
> -    return vring->vr.avail->idx != vring->last_avail_idx;
> +    return vring_get_avail_idx(vdev, vring) != vring->last_avail_idx;
>  }
> 
>  /* Fail future vring_pop() and vring_push() calls until reset */
> @@ -54,6 +111,7 @@ void vring_disable_notification(VirtIODevice *vdev, Vring *vring);
>  bool vring_enable_notification(VirtIODevice *vdev, Vring *vring);
>  bool vring_should_notify(VirtIODevice *vdev, Vring *vring);
>  int vring_pop(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem);
> -void vring_push(Vring *vring, VirtQueueElement *elem, int len);
> +void vring_push(VirtIODevice *vdev, Vring *vring, VirtQueueElement *elem,
> +                int len);
> 
>  #endif /* VRING_H */