From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42561) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fQHJf-00023h-Fk for qemu-devel@nongnu.org; Tue, 05 Jun 2018 15:08:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fQHJc-00032g-Hw for qemu-devel@nongnu.org; Tue, 05 Jun 2018 15:08:23 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:46868 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fQHJc-00032C-BM for qemu-devel@nongnu.org; Tue, 05 Jun 2018 15:08:20 -0400 From: wexu@redhat.com Date: Tue, 5 Jun 2018 15:07:58 -0400 Message-Id: <1528225683-11413-4-git-send-email-wexu@redhat.com> In-Reply-To: <1528225683-11413-1-git-send-email-wexu@redhat.com> References: <1528225683-11413-1-git-send-email-wexu@redhat.com> Subject: [Qemu-devel] [RFC v2 3/8] virtio: empty check and desc read for packed ring List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: jasowang@redhat.com, tiwei.bie@intel.com, mst@redhat.com, wexu@redhat.com, jfreimann@redhat.com From: Wei Xu helper for ring empty check and descriptor read. Signed-off-by: Wei Xu --- hw/virtio/virtio.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 59 insertions(+), 3 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index f6c0689..bd669a2 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -24,6 +24,9 @@ #include "hw/virtio/virtio-access.h" #include "sysemu/dma.h" +#define AVAIL_DESC_PACKED(b) ((b) << 7) +#define USED_DESC_PACKED(b) ((b) << 15) + /* * The alignment to use between consumer and producer parts of vring. * x86 pagesize again. This is the default, used by transports like PCI @@ -357,10 +360,27 @@ int virtio_queue_ready(VirtQueue *vq) return vq->vring.avail != 0; } +static void vring_packed_desc_read(VirtIODevice *vdev, VRingDescPacked *desc, + MemoryRegionCache *cache, int i) +{ + address_space_read_cached(cache, i * sizeof(VRingDescPacked), + desc, sizeof(VRingDescPacked)); + virtio_tswap64s(vdev, &desc->addr); + virtio_tswap32s(vdev, &desc->len); + virtio_tswap16s(vdev, &desc->id); + virtio_tswap16s(vdev, &desc->flags); +} + +static inline bool is_desc_avail(struct VRingDescPacked *desc) +{ + return !!(desc->flags & AVAIL_DESC_PACKED(1)) != + !!(desc->flags & USED_DESC_PACKED(1)); +} + /* Fetch avail_idx from VQ memory only when we really need to know if * guest has added some buffers. * Called within rcu_read_lock(). */ -static int virtio_queue_empty_rcu(VirtQueue *vq) +static int virtio_queue_split_empty_rcu(VirtQueue *vq) { if (unlikely(!vq->vring.avail)) { return 1; @@ -373,7 +393,7 @@ static int virtio_queue_empty_rcu(VirtQueue *vq) return vring_avail_idx(vq) == vq->last_avail_idx; } -int virtio_queue_empty(VirtQueue *vq) +static int virtio_queue_split_empty(VirtQueue *vq) { bool empty; @@ -391,6 +411,42 @@ int virtio_queue_empty(VirtQueue *vq) return empty; } +static int virtio_queue_packed_empty_rcu(VirtQueue *vq) +{ + struct VRingDescPacked desc; + VRingMemoryRegionCaches *cache; + + if (unlikely(!vq->vring.desc)) { + return 1; + } + + cache = vring_get_region_caches(vq); + vring_packed_desc_read(vq->vdev, &desc, &cache->desc, vq->last_avail_idx); + + /* Make sure we see the updated flag */ + smp_mb(); + return !is_desc_avail(&desc); +} + +static int virtio_queue_packed_empty(VirtQueue *vq) +{ + bool empty; + + rcu_read_lock(); + empty = virtio_queue_packed_empty_rcu(vq); + rcu_read_unlock(); + return empty; +} + +int virtio_queue_empty(VirtQueue *vq) +{ + if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) { + return virtio_queue_packed_empty(vq); + } else { + return virtio_queue_split_empty(vq); + } +} + static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len) { @@ -862,7 +918,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) return NULL; } rcu_read_lock(); - if (virtio_queue_empty_rcu(vq)) { + if (virtio_queue_split_empty_rcu(vq)) { goto done; } /* Needed after virtio_queue_empty(), see comment in -- 1.8.3.1