From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:52778 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932559AbcKHQro (ORCPT ); Tue, 8 Nov 2016 11:47:44 -0500 Subject: Patch "virtio_ring: Make interrupt suppression spec compliant" has been added to the 4.8-stable tree To: lprosek@redhat.com, gregkh@linuxfoundation.org, mst@redhat.com Cc: , From: Date: Tue, 08 Nov 2016 17:46:57 +0100 Message-ID: <147862361711480@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled virtio_ring: Make interrupt suppression spec compliant to the 4.8-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: virtio_ring-make-interrupt-suppression-spec-compliant.patch and it can be found in the queue-4.8 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 0ea1e4a6d9b62cf29e210d2b4ba9fd43917522e3 Mon Sep 17 00:00:00 2001 From: Ladi Prosek Date: Wed, 31 Aug 2016 14:00:04 +0200 Subject: virtio_ring: Make interrupt suppression spec compliant From: Ladi Prosek commit 0ea1e4a6d9b62cf29e210d2b4ba9fd43917522e3 upstream. According to the spec, if the VIRTIO_RING_F_EVENT_IDX feature bit is negotiated the driver MUST set flags to 0. Not dirtying the available ring in virtqueue_disable_cb also has a minor positive performance impact, improving L1 dcache load missed by ~0.5% in vring_bench. Writes to the used event field (vring_used_event) are still unconditional. Cc: Michael S. Tsirkin Signed-off-by: Ladi Prosek Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman --- drivers/virtio/virtio_ring.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -732,7 +732,8 @@ void virtqueue_disable_cb(struct virtque if (!(vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT)) { vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT; - vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow); + if (!vq->event) + vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow); } } @@ -764,7 +765,8 @@ unsigned virtqueue_enable_cb_prepare(str * entry. Always do both to keep code simple. */ if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) { vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT; - vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow); + if (!vq->event) + vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow); } vring_used_event(&vq->vring) = cpu_to_virtio16(_vq->vdev, last_used_idx = vq->last_used_idx); END_USE(vq); @@ -832,10 +834,11 @@ bool virtqueue_enable_cb_delayed(struct * more to do. */ /* Depending on the VIRTIO_RING_F_USED_EVENT_IDX feature, we need to * either clear the flags bit or point the event index at the next - * entry. Always do both to keep code simple. */ + * entry. Always update the event index to keep code simple. */ if (vq->avail_flags_shadow & VRING_AVAIL_F_NO_INTERRUPT) { vq->avail_flags_shadow &= ~VRING_AVAIL_F_NO_INTERRUPT; - vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow); + if (!vq->event) + vq->vring.avail->flags = cpu_to_virtio16(_vq->vdev, vq->avail_flags_shadow); } /* TODO: tune this threshold */ bufs = (u16)(vq->avail_idx_shadow - vq->last_used_idx) * 3 / 4; @@ -953,7 +956,8 @@ struct virtqueue *__vring_new_virtqueue( /* No callback? Tell other side not to bother us. */ if (!callback) { vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT; - vq->vring.avail->flags = cpu_to_virtio16(vdev, vq->avail_flags_shadow); + if (!vq->event) + vq->vring.avail->flags = cpu_to_virtio16(vdev, vq->avail_flags_shadow); } /* Put everything in free lists. */ Patches currently in stable-queue which might be from lprosek@redhat.com are queue-4.8/virtio_ring-make-interrupt-suppression-spec-compliant.patch