Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755891Ab1EDUw3 (ORCPT ); Wed, 4 May 2011 16:52:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:23566 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754279Ab1EDUwZ (ORCPT ); Wed, 4 May 2011 16:52:25 -0400 Date: Wed, 4 May 2011 23:51:56 +0300 From: "Michael S. Tsirkin" To: linux-kernel@vger.kernel.org Cc: Rusty Russell , Carsten Otte , Christian Borntraeger , linux390@de.ibm.com, Martin Schwidefsky , Heiko Carstens , Shirley Ma , lguest@lists.ozlabs.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, Krishna Kumar , Tom Lendacky , steved@us.ibm.com, habanero@linux.vnet.ibm.com Subject: [PATCH 10/18] vhost: utilize used_event index Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Mutt-Fcc: =sent User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7008 Lines: 206 Support the new used_event index. When acked, utilize it to reduce the # of interrupts sent to the guest. Signed-off-by: Michael S. Tsirkin --- drivers/vhost/vhost.c | 74 +++++++++++++++++++++++++++++++++++++------------ drivers/vhost/vhost.h | 7 ++++ 2 files changed, 63 insertions(+), 18 deletions(-) diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 2ab2912..e33d5a3 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -37,6 +37,8 @@ enum { VHOST_MEMORY_F_LOG = 0x1, }; +#define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num]) + static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh, poll_table *pt) { @@ -161,6 +163,8 @@ static void vhost_vq_reset(struct vhost_dev *dev, vq->last_avail_idx = 0; vq->avail_idx = 0; vq->last_used_idx = 0; + vq->signalled_used = 0; + vq->signalled_used_valid = false; vq->used_flags = 0; vq->log_used = false; vq->log_addr = -1ull; @@ -489,14 +493,15 @@ static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem, return 1; } -static int vq_access_ok(unsigned int num, +static int vq_access_ok(struct vhost_dev *d, unsigned int num, struct vring_desc __user *desc, struct vring_avail __user *avail, struct vring_used __user *used) { + size_t sa = vhost_has_feature(d, VIRTIO_RING_F_USED_EVENT_IDX) ? 2 : 0; return access_ok(VERIFY_READ, desc, num * sizeof *desc) && access_ok(VERIFY_READ, avail, - sizeof *avail + num * sizeof *avail->ring) && + sizeof *avail + num * sizeof *avail->ring + sa) && access_ok(VERIFY_WRITE, used, sizeof *used + num * sizeof *used->ring); } @@ -531,7 +536,7 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base) /* Caller should have vq mutex and device mutex */ int vhost_vq_access_ok(struct vhost_virtqueue *vq) { - return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) && + return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) && vq_log_access_ok(vq, vq->log_base); } @@ -577,6 +582,7 @@ static int init_used(struct vhost_virtqueue *vq, if (r) return r; + vq->signalled_used_valid = false; return get_user(vq->last_used_idx, &used->idx); } @@ -674,7 +680,7 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp) * If it is not, we don't as size might not have been setup. * We will verify when backend is configured. */ if (vq->private_data) { - if (!vq_access_ok(vq->num, + if (!vq_access_ok(d, vq->num, (void __user *)(unsigned long)a.desc_user_addr, (void __user *)(unsigned long)a.avail_user_addr, (void __user *)(unsigned long)a.used_user_addr)) { @@ -1267,6 +1273,12 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len) eventfd_signal(vq->log_ctx, 1); } vq->last_used_idx++; + /* If the driver never bothers to signal in a very long while, + * used index might wrap around. If that happens, invalidate + * signalled_used index we stored. TODO: make sure driver + * signals at least once in 2^16 and remove this. */ + if (unlikely(vq->last_used_idx == vq->signalled_used)) + vq->signalled_used_valid = false; return 0; } @@ -1275,6 +1287,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq, unsigned count) { struct vring_used_elem __user *used; + u16 old, new; int start; start = vq->last_used_idx % vq->num; @@ -1292,7 +1305,14 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq, ((void __user *)used - (void __user *)vq->used), count * sizeof *used); } - vq->last_used_idx += count; + old = vq->last_used_idx; + new = (vq->last_used_idx += count); + /* If the driver never bothers to signal in a very long while, + * used index might wrap around. If that happens, invalidate + * signalled_used index we stored. TODO: make sure driver + * signals at least once in 2^16 and remove this. */ + if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old))) + vq->signalled_used_valid = false; return 0; } @@ -1331,29 +1351,47 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads, return r; } -/* This actually signals the guest, using eventfd. */ -void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq) +static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq) { - __u16 flags; - + __u16 old, new, event; + bool v; /* Flush out used index updates. This is paired * with the barrier that the Guest executes when enabling * interrupts. */ smp_mb(); - if (__get_user(flags, &vq->avail->flags)) { - vq_err(vq, "Failed to get flags"); - return; + if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) && + unlikely(vq->avail_idx == vq->last_avail_idx)) + return true; + + if (!vhost_has_feature(dev, VIRTIO_RING_F_USED_EVENT_IDX)) { + __u16 flags; + if (__get_user(flags, &vq->avail->flags)) { + vq_err(vq, "Failed to get flags"); + return true; + } + return !(flags & VRING_AVAIL_F_NO_INTERRUPT); } + old = vq->signalled_used; + v = vq->signalled_used_valid; + new = vq->signalled_used = vq->last_used_idx; + vq->signalled_used_valid = true; - /* If they don't want an interrupt, don't signal, unless empty. */ - if ((flags & VRING_AVAIL_F_NO_INTERRUPT) && - (vq->avail_idx != vq->last_avail_idx || - !vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY))) - return; + if (unlikely(!v)) + return true; + + if (get_user(event, vhost_used_event(vq))) { + vq_err(vq, "Failed to get used event idx"); + return true; + } + return vring_need_event(event, new, old); +} +/* This actually signals the guest, using eventfd. */ +void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq) +{ /* Signal the Guest tell them we used something up. */ - if (vq->call_ctx) + if (vq->call_ctx && vhost_notify(dev, vq)) eventfd_signal(vq->call_ctx, 1); } diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index 0f1bf33..5825ac6 100644 --- a/drivers/vhost/vhost.h +++ b/drivers/vhost/vhost.h @@ -84,6 +84,12 @@ struct vhost_virtqueue { /* Used flags */ u16 used_flags; + /* Last used index value we have signalled on */ + u16 signalled_used; + + /* Last used index value we have signalled on */ + bool signalled_used_valid; + /* Log writes to used structure. */ bool log_used; u64 log_addr; @@ -164,6 +170,7 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log, enum { VHOST_FEATURES = (1 << VIRTIO_F_NOTIFY_ON_EMPTY) | (1 << VIRTIO_RING_F_INDIRECT_DESC) | + (1 << VIRTIO_RING_F_USED_EVENT_IDX) | (1 << VHOST_F_LOG_ALL) | (1 << VHOST_NET_F_VIRTIO_NET_HDR) | (1 << VIRTIO_NET_F_MRG_RXBUF), -- 1.7.5.53.gc233e -- 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/