Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757779AbaGAKrk (ORCPT ); Tue, 1 Jul 2014 06:47:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48969 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756433AbaGAKri (ORCPT ); Tue, 1 Jul 2014 06:47:38 -0400 Date: Tue, 1 Jul 2014 13:49:31 +0300 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Rusty Russell , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Jason Wang Subject: [PATCH RFC 1/2] virtio: support for urgent descriptors Message-ID: <1404203661-7521-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Mutt-Fcc: =sent Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Below should be useful for some experiments Jason is doing. I thought I'd send it out for early review/feedback. Compiled-only at this point. event idx feature allows us to defer interrupts until a specific # of descriptors were used. Sometimes it might be useful to get an interrupt after a specific descriptor, regardless. This adds a descriptor flag for this, and an API to create an urgent output descriptor. This is still an RFC: we'll need a feature bit for drivers to detect this, but we've run out of feature bits for virtio 0.X. For experimentation purposes, drivers can assume this is set, or add a driver-specific feature bit. Signed-off-by: Michael S. Tsirkin --- include/linux/virtio.h | 6 ++++++ include/uapi/linux/virtio_ring.h | 3 +++ drivers/virtio/virtio_ring.c | 46 ++++++++++++++++++++++++++++++++++++---- 3 files changed, 51 insertions(+), 4 deletions(-) diff --git a/include/linux/virtio.h b/include/linux/virtio.h index b46671e..14625a6 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -39,6 +39,12 @@ int virtqueue_add_outbuf(struct virtqueue *vq, void *data, gfp_t gfp); +int virtqueue_add_outbuf_urgent(struct virtqueue *vq, + struct scatterlist sg[], unsigned int num, + void *data, + gfp_t gfp); + + int virtqueue_add_inbuf(struct virtqueue *vq, struct scatterlist sg[], unsigned int num, void *data, diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h index a99f9b7..d08b1e6 100644 --- a/include/uapi/linux/virtio_ring.h +++ b/include/uapi/linux/virtio_ring.h @@ -39,6 +39,9 @@ #define VRING_DESC_F_WRITE 2 /* This means the buffer contains a list of buffer descriptors. */ #define VRING_DESC_F_INDIRECT 4 +/* This means the descriptor should cause an interrupt + * ignoring avail event idx. */ +#define VRING_DESC_F_URGENT 8 /* The Host uses this in used->flags to advise the Guest: don't kick me when * you add a buffer. It's unreliable, so it's simply an optimization. Guest diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 4d08f45a..3e448b9 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -115,6 +115,7 @@ static inline struct scatterlist *sg_next_arr(struct scatterlist *sg, /* Set up an indirect table of descriptors and add it to the queue. */ static inline int vring_add_indirect(struct vring_virtqueue *vq, + bool urgent, struct scatterlist *sgs[], struct scatterlist *(*next) (struct scatterlist *, unsigned int *), @@ -173,6 +174,8 @@ static inline int vring_add_indirect(struct vring_virtqueue *vq, /* Use a single buffer which doesn't continue */ head = vq->free_head; vq->vring.desc[head].flags = VRING_DESC_F_INDIRECT; + if (urgent) + vq->vring.desc[head].flags |= VRING_DESC_F_URGENT; vq->vring.desc[head].addr = virt_to_phys(desc); /* kmemleak gives a false positive, as it's hidden by virt_to_phys */ kmemleak_ignore(desc); @@ -185,6 +188,7 @@ static inline int vring_add_indirect(struct vring_virtqueue *vq, } static inline int virtqueue_add(struct virtqueue *_vq, + bool urgent, struct scatterlist *sgs[], struct scatterlist *(*next) (struct scatterlist *, unsigned int *), @@ -227,7 +231,7 @@ static inline int virtqueue_add(struct virtqueue *_vq, /* If the host supports indirect descriptor tables, and we have multiple * buffers, then go indirect. FIXME: tune this threshold */ if (vq->indirect && total_sg > 1 && vq->vq.num_free) { - head = vring_add_indirect(vq, sgs, next, total_sg, total_out, + head = vring_add_indirect(vq, urgent, sgs, next, total_sg, total_out, total_in, out_sgs, in_sgs, gfp); if (likely(head >= 0)) @@ -256,6 +260,10 @@ static inline int virtqueue_add(struct virtqueue *_vq, for (n = 0; n < out_sgs; n++) { for (sg = sgs[n]; sg; sg = next(sg, &total_out)) { vq->vring.desc[i].flags = VRING_DESC_F_NEXT; + if (urgent) { + vq->vring.desc[head].flags |= VRING_DESC_F_URGENT; + urgent = false; + } vq->vring.desc[i].addr = sg_phys(sg); vq->vring.desc[i].len = sg->length; prev = i; @@ -265,6 +273,10 @@ static inline int virtqueue_add(struct virtqueue *_vq, for (; n < (out_sgs + in_sgs); n++) { for (sg = sgs[n]; sg; sg = next(sg, &total_in)) { vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE; + if (urgent) { + vq->vring.desc[head].flags |= VRING_DESC_F_URGENT; + urgent = false; + } vq->vring.desc[i].addr = sg_phys(sg); vq->vring.desc[i].len = sg->length; prev = i; @@ -305,6 +317,8 @@ add_head: /** * virtqueue_add_sgs - expose buffers to other end + * @urgent: in case virtqueue_enable_cb_delayed was called, cause an interrupt + * after this descriptor was completed * @vq: the struct virtqueue we're talking about. * @sgs: array of terminated scatterlists. * @out_num: the number of scatterlists readable by other side @@ -337,7 +351,7 @@ int virtqueue_add_sgs(struct virtqueue *_vq, for (sg = sgs[i]; sg; sg = sg_next(sg)) total_in++; } - return virtqueue_add(_vq, sgs, sg_next_chained, + return virtqueue_add(_vq, false, sgs, sg_next_chained, total_out, total_in, out_sgs, in_sgs, data, gfp); } EXPORT_SYMBOL_GPL(virtqueue_add_sgs); @@ -360,11 +374,35 @@ int virtqueue_add_outbuf(struct virtqueue *vq, void *data, gfp_t gfp) { - return virtqueue_add(vq, &sg, sg_next_arr, num, 0, 1, 0, data, gfp); + return virtqueue_add(vq, false, &sg, sg_next_arr, num, 0, 1, 0, data, gfp); } EXPORT_SYMBOL_GPL(virtqueue_add_outbuf); /** + * virtqueue_add_outbuf - expose output buffers to other end + * in case virtqueue_enable_cb_delayed was called, cause an interrupt + * after this descriptor was completed + * @vq: the struct virtqueue we're talking about. + * @sgs: array of scatterlists (need not be terminated!) + * @num: the number of scatterlists readable by other side + * @data: the token identifying the buffer. + * @gfp: how to do memory allocations (if necessary). + * + * Caller must ensure we don't call this with other virtqueue operations + * at the same time (except where noted). + * + * Returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO). + */ +int virtqueue_add_outbuf_urgent(struct virtqueue *vq, + struct scatterlist sg[], unsigned int num, + void *data, + gfp_t gfp) +{ + return virtqueue_add(vq, true, &sg, sg_next_arr, num, 0, 1, 0, data, gfp); +} +EXPORT_SYMBOL_GPL(virtqueue_add_outbuf_urgent); + +/** * virtqueue_add_inbuf - expose input buffers to other end * @vq: the struct virtqueue we're talking about. * @sgs: array of scatterlists (need not be terminated!) @@ -382,7 +420,7 @@ int virtqueue_add_inbuf(struct virtqueue *vq, void *data, gfp_t gfp) { - return virtqueue_add(vq, &sg, sg_next_arr, 0, num, 0, 1, data, gfp); + return virtqueue_add(vq, false, &sg, sg_next_arr, 0, num, 0, 1, data, gfp); } EXPORT_SYMBOL_GPL(virtqueue_add_inbuf); -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/