From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH] vhost: fix vhost interrupt support Date: Mon, 10 Sep 2018 09:48:24 +0200 Message-ID: References: <20180904235555.31839-1-tiwei.bie@intel.com> <20180910073637.GA25254@debian> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: zhihong.wang@intel.com, dev@dpdk.org, stable@dpdk.org To: Tiwei Bie Return-path: In-Reply-To: <20180910073637.GA25254@debian> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 09/10/2018 09:36 AM, Tiwei Bie wrote: > Hi Maxime, > > On Mon, Sep 10, 2018 at 09:22:00AM +0200, Maxime Coquelin wrote: >> Hi Tiwei, >> >> On 09/05/2018 01:55 AM, Tiwei Bie wrote: >>> When VIRTIO_RING_F_EVENT_IDX is negotiated, we need to >>> update the avail event to enable the notification. >>> >>> Fixes: 3f8ff12821e4 ("vhost: support interrupt mode") >>> Cc: stable@dpdk.org >>> >>> Signed-off-by: Tiwei Bie >>> --- >>> lib/librte_vhost/Makefile | 1 + >>> lib/librte_vhost/vhost.c | 18 ++++++++++++------ >>> lib/librte_vhost/vhost.h | 2 ++ >>> 3 files changed, 15 insertions(+), 6 deletions(-) >>> >>> diff --git a/lib/librte_vhost/Makefile b/lib/librte_vhost/Makefile >>> index de431fbb7..531cf4832 100644 >>> --- a/lib/librte_vhost/Makefile >>> +++ b/lib/librte_vhost/Makefile >>> @@ -13,6 +13,7 @@ LIBABIVER := 4 >>> CFLAGS += -DALLOW_EXPERIMENTAL_API >>> CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR) -O3 -D_FILE_OFFSET_BITS=64 >>> CFLAGS += -I vhost_user >>> +CFLAGS += -fno-strict-aliasing >> >> I'm not clear why this is needed looking at the code below, >> could you please explain? > > Without this, we will get below build error: > > lib/librte_vhost/vhost.c: In function ‘vhost_enable_notify_split’: > lib/librte_vhost/vhost.h:656:4: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing] > (*(volatile uint16_t*)&(vr)->used->ring[(vr)->size]) > ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > lib/librte_vhost/vhost.c:659:4: note: in expansion of macro ‘vhost_avail_event’ > vhost_avail_event(vq) = vq->last_avail_idx; > ^~~~~~~~~~~~~~~~~ > cc1: all warnings being treated as errors OK, thanks for the info. Reviewed-by: Maxime Coquelin Maxime