From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751425AbeECJ5m (ORCPT ); Thu, 3 May 2018 05:57:42 -0400 Received: from mga04.intel.com ([192.55.52.120]:51315 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751050AbeECJ5k (ORCPT ); Thu, 3 May 2018 05:57:40 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.49,358,1520924400"; d="scan'208";a="36542217" Date: Thu, 3 May 2018 17:58:23 +0800 From: Tiwei Bie To: Jason Wang Cc: mst@redhat.com, pbonzini@redhat.com, stefanha@redhat.com, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, dan.daly@intel.com, cunming.liang@intel.com, zhihong.wang@intel.com Subject: Re: [RFC] virtio: support VIRTIO_F_IO_BARRIER Message-ID: <20180503095823.zpxskdts7etpwl6x@debian> References: <20180503025955.28816-1-tiwei.bie@intel.com> <20180503083015.kb7po26ga46g66tc@debian> <1292c46c-34ad-ea21-1f05-164044a5f35a@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1292c46c-34ad-ea21-1f05-164044a5f35a@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 03, 2018 at 05:09:44PM +0800, Jason Wang wrote: > On 2018年05月03日 16:30, Tiwei Bie wrote: > > On Thu, May 03, 2018 at 03:30:03PM +0800, Jason Wang wrote: > > > On 2018年05月03日 10:59, Tiwei Bie wrote: > > > > This patch introduces the support for VIRTIO_F_IO_BARRIER. > > > > When this feature is negotiated, driver will use the barriers > > > > suitable for hardware devices. > > > > > > > > Signed-off-by: Tiwei Bie > > > > --- > > > > drivers/virtio/virtio_ring.c | 5 +++++ > > > > include/uapi/linux/virtio_config.h | 8 +++++++- > > > > 2 files changed, 12 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > > index 21d464a29cf8..edb565643bf4 100644 > > > > --- a/drivers/virtio/virtio_ring.c > > > > +++ b/drivers/virtio/virtio_ring.c > > > > @@ -996,6 +996,9 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > > > > !context; > > > > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > > > > + if (virtio_has_feature(vdev, VIRTIO_F_IO_BARRIER)) > > > > + vq->weak_barriers = false; > > > > + > > > > /* No callback? Tell other side not to bother us. */ > > > > if (!callback) { > > > > vq->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT; > > > > @@ -1164,6 +1167,8 @@ void vring_transport_features(struct virtio_device *vdev) > > > > break; > > > > case VIRTIO_F_IOMMU_PLATFORM: > > > > break; > > > > + case VIRTIO_F_IO_BARRIER: > > > > + break; > > > > default: > > > > /* We don't understand this bit. */ > > > > __virtio_clear_bit(vdev, i); > > > > diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h > > > > index 308e2096291f..6ca8d24bf468 100644 > > > > --- a/include/uapi/linux/virtio_config.h > > > > +++ b/include/uapi/linux/virtio_config.h > > > > @@ -49,7 +49,7 @@ > > > > * transport being used (eg. virtio_ring), the rest are per-device feature > > > > * bits. */ > > > > #define VIRTIO_TRANSPORT_F_START 28 > > > > -#define VIRTIO_TRANSPORT_F_END 34 > > > > +#define VIRTIO_TRANSPORT_F_END 38 > > > > #ifndef VIRTIO_CONFIG_NO_LEGACY > > > > /* Do we get callbacks when the ring is completely used, even if we've > > > > @@ -71,4 +71,10 @@ > > > > * this is for compatibility with legacy systems. > > > > */ > > > > #define VIRTIO_F_IOMMU_PLATFORM 33 > > > > + > > > > +/* > > > > + * If clear - driver may use barriers suitable for CPU cores. > > > > + * If set - driver must use barriers suitable for hardware devices. > > > > + */ > > > > +#define VIRTIO_F_IO_BARRIER 37 > > > > #endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */ > > > Hi: > > > > > > I believe this depends on Michael's patch of > > > > > > "[PATCH] virtio_ring: switch to dma_XX barriers for rpmsg" > > > > > > ? > > > > > > Thanks > > We already have below commit and some other related commits > > in the tree: > > > > 7b21e34fd1c2 ("virtio: harsher barriers for rpmsg.") > > > > They should have already guaranteed that virtio_Xmb() will > > be OK for hardware devices when vq->weak_barriers is false. > > If my understanding is correct, the barriers used in this > > case are overkill. So Michael's patch is to make the barriers > > weaker (or better). > > > > Best regards, > > Tiwei Bie > > Well, I think we need dma barriers for some platforms according to previous > discussion? Without Michael's patch, we won't use any dma barriers in fact > for virtio. You are right. Thanks! Are you suggesting to add a reference to Michael's patch in this patch to make sure that it won't be applied before that patch? Best regards, Tiwei Bie > > Thanks