From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751598AbeEVIRg (ORCPT ); Tue, 22 May 2018 04:17:36 -0400 Received: from mga05.intel.com ([192.55.52.43]:23522 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751479AbeEVIRY (ORCPT ); Tue, 22 May 2018 04:17:24 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.49,429,1520924400"; d="scan'208";a="51200179" From: Tiwei Bie To: mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org Cc: wexu@redhat.com, jfreimann@redhat.com, tiwei.bie@intel.com Subject: [RFC v5 4/5] virtio_ring: add event idx support in packed ring Date: Tue, 22 May 2018 16:16:47 +0800 Message-Id: <20180522081648.14768-5-tiwei.bie@intel.com> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180522081648.14768-1-tiwei.bie@intel.com> References: <20180522081648.14768-1-tiwei.bie@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit introduces the EVENT_IDX support in packed ring. Signed-off-by: Tiwei Bie --- drivers/virtio/virtio_ring.c | 67 ++++++++++++++++++++++++++++++++++-- 1 file changed, 64 insertions(+), 3 deletions(-) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index eb9fd5207a68..1ee52a89cb04 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1043,7 +1043,7 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq, static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); - u16 flags; + u16 new, old, off_wrap, flags, wrap_counter, event_idx; bool needs_kick; u32 snapshot; @@ -1052,9 +1052,19 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) * suppressions. */ virtio_mb(vq->weak_barriers); + old = vq->next_avail_idx - vq->num_added; + new = vq->next_avail_idx; + vq->num_added = 0; + snapshot = *(u32 *)vq->vring_packed.device; + off_wrap = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot & 0xffff)); flags = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot >> 16)) & 0x3; + wrap_counter = off_wrap >> 15; + event_idx = off_wrap & ~(1<<15); + if (wrap_counter != vq->avail_wrap_counter) + event_idx -= vq->vring_packed.num; + #ifdef DEBUG if (vq->last_add_time_valid) { WARN_ON(ktime_to_ms(ktime_sub(ktime_get(), @@ -1063,7 +1073,10 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq) vq->last_add_time_valid = false; #endif - needs_kick = (flags != VRING_EVENT_F_DISABLE); + if (flags == VRING_EVENT_F_DESC) + needs_kick = vring_need_event(event_idx, new, old); + else + needs_kick = (flags != VRING_EVENT_F_DISABLE); END_USE(vq); return needs_kick; } @@ -1170,6 +1183,15 @@ static void *virtqueue_get_buf_ctx_packed(struct virtqueue *_vq, ret = vq->desc_state_packed[id].data; detach_buf_packed(vq, id, ctx); + /* If we expect an interrupt for the next entry, tell host + * by writing event index and flush out the write before + * the read in the next get_buf call. */ + if (vq->event_flags_shadow == VRING_EVENT_F_DESC) + virtio_store_mb(vq->weak_barriers, + &vq->vring_packed.driver->off_wrap, + cpu_to_virtio16(_vq->vdev, vq->last_used_idx | + ((u16)vq->used_wrap_counter << 15))); + #ifdef DEBUG vq->last_add_time_valid = false; #endif @@ -1197,10 +1219,26 @@ static unsigned virtqueue_enable_cb_prepare_packed(struct virtqueue *_vq) /* We optimistically turn back on interrupts, then check if there was * more to do. */ + /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to + * either clear the flags bit or point the event index at the next + * entry. Always update the event index to keep code simple. */ + + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, + vq->last_used_idx | + ((u16)vq->used_wrap_counter << 15)); if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { virtio_wmb(vq->weak_barriers); + // XXX XXX XXX + // Setting VRING_EVENT_F_DESC in this function + // will break netperf test for now. + // Will need to look into this. +#if 0 + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : + VRING_EVENT_F_ENABLE; +#else vq->event_flags_shadow = VRING_EVENT_F_ENABLE; +#endif vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, vq->event_flags_shadow); } @@ -1227,15 +1265,38 @@ static bool virtqueue_poll_packed(struct virtqueue *_vq, unsigned last_used_idx) static bool virtqueue_enable_cb_delayed_packed(struct virtqueue *_vq) { struct vring_virtqueue *vq = to_vvq(_vq); + u16 bufs, used_idx, wrap_counter; START_USE(vq); /* We optimistically turn back on interrupts, then check if there was * more to do. */ + /* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to + * either clear the flags bit or point the event index at the next + * entry. Always update the event index to keep code simple. */ + + /* TODO: tune this threshold */ + if (vq->next_avail_idx < vq->last_used_idx) + bufs = (vq->vring_packed.num + vq->next_avail_idx - + vq->last_used_idx) * 3 / 4; + else + bufs = (vq->next_avail_idx - vq->last_used_idx) * 3 / 4; + + wrap_counter = vq->used_wrap_counter; + + used_idx = vq->last_used_idx + bufs; + if (used_idx >= vq->vring_packed.num) { + used_idx -= vq->vring_packed.num; + wrap_counter ^= 1; + } + + vq->vring_packed.driver->off_wrap = cpu_to_virtio16(_vq->vdev, + used_idx | (wrap_counter << 15)); if (vq->event_flags_shadow == VRING_EVENT_F_DISABLE) { virtio_wmb(vq->weak_barriers); - vq->event_flags_shadow = VRING_EVENT_F_ENABLE; + vq->event_flags_shadow = vq->event ? VRING_EVENT_F_DESC : + VRING_EVENT_F_ENABLE; vq->vring_packed.driver->flags = cpu_to_virtio16(_vq->vdev, vq->event_flags_shadow); } -- 2.17.0