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Tue, 5 Jun 2018 19:08:29 +0000 (UTC) From: wexu@redhat.com To: qemu-devel@nongnu.org Date: Tue, 5 Jun 2018 15:08:02 -0400 Message-Id: <1528225683-11413-8-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> X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Tue, 05 Jun 2018 19:08:31 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Tue, 05 Jun 2018 19:08:31 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'wexu@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: [Qemu-devel] [RFC v2 7/8] virtio: event suppression for packed ring X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: jasowang@redhat.com, jfreimann@redhat.com, wexu@redhat.com, tiwei.bie@intel.com, mst@redhat.com Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Wei Xu Signed-off-by: Wei Xu Signed-off-by: Wei Xu --- hw/virtio/virtio.c | 115 +++++++++++++++++++++++-- include/standard-headers/linux/virtio_config.h | 13 +++ 2 files changed, 119 insertions(+), 9 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 6f2da83..4543974 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -226,6 +226,24 @@ static void vring_desc_read(VirtIODevice *vdev, VRingDesc *desc, virtio_tswap16s(vdev, &desc->next); } +static void vring_packed_event_read(VirtIODevice *vdev, + MemoryRegionCache *cache, VRingPackedDescEvent *e) +{ + address_space_read_cached(cache, 0, e, sizeof(*e)); + virtio_tswap16s(vdev, &e->off_wrap); + virtio_tswap16s(vdev, &e->flags); +} + +static void vring_packed_event_write(VirtIODevice *vdev, + MemoryRegionCache *cache, VRingPackedDescEvent *e) +{ + virtio_tswap16s(vdev, &e->off_wrap); + virtio_tswap16s(vdev, &e->flags); + address_space_write_cached(cache, 0, e, sizeof(*e)); + address_space_cache_invalidate(cache, 0, sizeof(VRingUsedElem)); +} + + static VRingMemoryRegionCaches *vring_get_region_caches(struct VirtQueue *vq) { VRingMemoryRegionCaches *caches = atomic_rcu_read(&vq->vring.caches); @@ -332,14 +350,8 @@ static inline void vring_set_avail_event(VirtQueue *vq, uint16_t val) address_space_cache_invalidate(&caches->used, pa, sizeof(val)); } -void virtio_queue_set_notification(VirtQueue *vq, int enable) +static void virtio_queue_set_notification_split(VirtQueue *vq, int enable) { - vq->notification = enable; - - if (!vq->vring.desc) { - return; - } - rcu_read_lock(); if (virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX)) { vring_set_avail_event(vq, vring_avail_idx(vq)); @@ -355,6 +367,38 @@ void virtio_queue_set_notification(VirtQueue *vq, int enable) rcu_read_unlock(); } +static void virtio_queue_set_notification_packed(VirtQueue *vq, int enable) +{ + VRingPackedDescEvent e; + VRingMemoryRegionCaches *caches; + + rcu_read_lock(); + caches = vring_get_region_caches(vq); + vring_packed_event_read(vq->vdev, &caches->device, &e); + if (enable) { + e.flags = RING_EVENT_FLAGS_ENABLE; + } else { + e.flags = RING_EVENT_FLAGS_DISABLE; + } + vring_packed_event_write(vq->vdev, &caches->device, &e); + rcu_read_unlock(); +} + +void virtio_queue_set_notification(VirtQueue *vq, int enable) +{ + vq->notification = enable; + + if (!vq->vring.desc) { + return; + } + + if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) { + virtio_queue_set_notification_packed(vq, enable); + } else { + virtio_queue_set_notification_split(vq, enable); + } +} + int virtio_queue_ready(VirtQueue *vq) { return vq->vring.avail != 0; @@ -2059,8 +2103,7 @@ static void virtio_set_isr(VirtIODevice *vdev, int value) } } -/* Called within rcu_read_lock(). */ -static bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq) +static bool virtio_split_should_notify(VirtIODevice *vdev, VirtQueue *vq) { uint16_t old, new; bool v; @@ -2083,6 +2126,60 @@ static bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq) return !v || vring_need_event(vring_get_used_event(vq), new, old); } +static bool vring_packed_need_event(VirtQueue *vq, uint16_t off_wrap, + uint16_t new, uint16_t old) +{ + bool wrap = vq->used_wrap_counter; + int off = off_wrap & ~(1 << 15); + + if (new < old) { + new += vq->vring.num; + wrap ^= 1; + } + + if (wrap != off_wrap >> 15) { + off += vq->vring.num; + } + + return vring_need_event(off, new, old); +} + +static bool virtio_packed_should_notify(VirtIODevice *vdev, VirtQueue *vq) +{ + VRingPackedDescEvent e; + uint16_t old, new; + bool v; + VRingMemoryRegionCaches *caches; + + caches = vring_get_region_caches(vq); + vring_packed_event_read(vdev, &caches->driver, &e); + + /* Make sure we see the updated flags */ + smp_mb(); + if (e.flags == RING_EVENT_FLAGS_DISABLE) { + return false; + } else if (e.flags == RING_EVENT_FLAGS_ENABLE) { + return true; + } + + v = vq->signalled_used_valid; + vq->signalled_used_valid = true; + old = vq->signalled_used; + new = vq->signalled_used = vq->used_idx; + + return !v || vring_packed_need_event(vq, e.off_wrap, new, old); +} + +/* Called within rcu_read_lock(). */ +static bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq) +{ + if (virtio_vdev_has_feature(vdev, VIRTIO_F_RING_PACKED)) { + return virtio_packed_should_notify(vdev, vq); + } else { + return virtio_split_should_notify(vdev, vq); + } +} + void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq) { bool should_notify; diff --git a/include/standard-headers/linux/virtio_config.h b/include/standard-headers/linux/virtio_config.h index 6ee5529..53e5c83 100644 --- a/include/standard-headers/linux/virtio_config.h +++ b/include/standard-headers/linux/virtio_config.h @@ -73,4 +73,17 @@ #define VIRTIO_F_IOMMU_PLATFORM 33 #define VIRTIO_F_RING_PACKED 34 + +/* Enable events */ +#define RING_EVENT_FLAGS_ENABLE 0x0 +/* Disable events */ +#define RING_EVENT_FLAGS_DISABLE 0x1 +/* + * * Enable events for a specific descriptor + * * (as specified by Descriptor Ring Change Event Offset/Wrap Counter). + * * Only valid if VIRTIO_F_RING_EVENT_IDX has been negotiated. + * */ +#define RING_EVENT_FLAGS_DESC 0x2 +/* The value 0x3 is reserved */ + #endif /* _LINUX_VIRTIO_CONFIG_H */