From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id 80ED45913 for ; Wed, 2 Dec 2015 15:36:31 +0100 (CET) Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga101.fm.intel.com with ESMTP; 02 Dec 2015 06:36:30 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,373,1444719600"; d="scan'208";a="852305558" Received: from yliu-dev.sh.intel.com (HELO yliu-dev) ([10.239.66.49]) by fmsmga001.fm.intel.com with ESMTP; 02 Dec 2015 06:36:31 -0800 Date: Wed, 2 Dec 2015 22:39:57 +0800 From: Yuanhan Liu To: Victor Kaplansky Message-ID: <20151202143957.GU2325@yliu-dev.sh.intel.com> References: <1449027793-30975-1-git-send-email-yuanhan.liu@linux.intel.com> <1449027793-30975-3-git-send-email-yuanhan.liu@linux.intel.com> <20151202153050-mutt-send-email-victork@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151202153050-mutt-send-email-victork@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Cc: dev@dpdk.org, "Michael S. Tsirkin" Subject: Re: [dpdk-dev] [PATCH 2/4] vhost: introduce vhost_log_write X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 02 Dec 2015 14:36:32 -0000 On Wed, Dec 02, 2015 at 03:53:01PM +0200, Victor Kaplansky wrote: > On Wed, Dec 02, 2015 at 11:43:11AM +0800, Yuanhan Liu wrote: > > Introduce vhost_log_write() helper function to log the dirty pages we > > touched. Page size is harded code to 4096 (VHOST_LOG_PAGE), and each > > log is presented by 1 bit. > > > > Therefore, vhost_log_write() simply finds the right bit for related > > page we are gonna change, and set it to 1. dev->log_base denotes the > > start of the dirty page bitmap. > > > > The page address is biased by log_guest_addr, which is derived from > > SET_VRING_ADDR request as part of the vring related addresses. > > > > Signed-off-by: Yuanhan Liu > > --- > > lib/librte_vhost/rte_virtio_net.h | 34 ++++++++++++++++++++++++++++++++++ > > lib/librte_vhost/virtio-net.c | 4 ++++ > > 2 files changed, 38 insertions(+) > > > > diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h > > index 416dac2..191c1be 100644 > > --- a/lib/librte_vhost/rte_virtio_net.h > > +++ b/lib/librte_vhost/rte_virtio_net.h > > @@ -40,6 +40,7 @@ > > */ > > > > #include > > +#include > > #include > > #include > > #include > > @@ -59,6 +60,8 @@ struct rte_mbuf; > > /* Backend value set by guest. */ > > #define VIRTIO_DEV_STOPPED -1 > > > > +#define VHOST_LOG_PAGE 4096 > > + > > > > /* Enum for virtqueue management. */ > > enum {VIRTIO_RXQ, VIRTIO_TXQ, VIRTIO_QNUM}; > > @@ -82,6 +85,7 @@ struct vhost_virtqueue { > > struct vring_desc *desc; /**< Virtqueue descriptor ring. */ > > struct vring_avail *avail; /**< Virtqueue available ring. */ > > struct vring_used *used; /**< Virtqueue used ring. */ > > + uint64_t log_guest_addr; /**< Physical address of used ring, for logging */ > > uint32_t size; /**< Size of descriptor ring. */ > > uint32_t backend; /**< Backend value to determine if device should started/stopped. */ > > uint16_t vhost_hlen; /**< Vhost header length (varies depending on RX merge buffers. */ > > @@ -203,6 +207,36 @@ gpa_to_vva(struct virtio_net *dev, uint64_t guest_pa) > > return vhost_va; > > } > > > > +static inline void __attribute__((always_inline)) > > +vhost_log_page(uint8_t *log_base, uint64_t page) > > +{ > > + /* TODO: to make it atomic? */ > > + log_base[page / 8] |= 1 << (page % 8); > > I think the atomic OR operation is necessary only if there can be > more than one vhost-user back-end updating the guest's memory > simultaneously. However probably it is pretty safe to perform > regular OR operation, since rings are not shared between > back-end. What about buffers pointed by descriptors? To be on > the safe side, I would use a GCC built-in function > __sync_fetch_and_or(). The build has to be passed not only for gcc, but for icc and clang as well. > > > +} > > + > > +static inline void __attribute__((always_inline)) > > +vhost_log_write(struct virtio_net *dev, struct vhost_virtqueue *vq, > > + uint64_t offset, uint64_t len) > > +{ > > + uint64_t addr = vq->log_guest_addr; > > + uint64_t page; > > + > > + if (unlikely(((dev->features & (1ULL << VHOST_F_LOG_ALL)) == 0) || > > + !dev->log_base || !len)) > > + return; > > Isn't "likely" more appropriate in above, since the whole > expression is expected to be true most of the time? Sorry, it's a typo, and thanks for the catching. --yliu