From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH net-next RFC 1/3] virtio: support for urgent descriptors Date: Fri, 17 Oct 2014 13:23:42 +0800 Message-ID: <5440A7DE.5030806@redhat.com> References: <1413011806-3813-1-git-send-email-jasowang@redhat.com> <1413011806-3813-2-git-send-email-jasowang@redhat.com> <877g01c2ml.fsf@rustcorp.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: linux-api@vger.kernel.org, kvm@vger.kernel.org To: Rusty Russell , mst@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: In-Reply-To: <877g01c2ml.fsf@rustcorp.com.au> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org List-Id: netdev.vger.kernel.org On 10/15/2014 01:40 PM, Rusty Russell wrote: > Jason Wang writes: >> Below should be useful for some experiments Jason is doing. >> I thought I'd send it out for early review/feedback. >> >> event idx feature allows us to defer interrupts until >> a specific # of descriptors were used. >> Sometimes it might be useful to get an interrupt after >> a specific descriptor, regardless. >> This adds a descriptor flag for this, and an API >> to create an urgent output descriptor. >> This is still an RFC: >> we'll need a feature bit for drivers to detect this, >> but we've run out of feature bits for virtio 0.X. >> For experimentation purposes, drivers can assume >> this is set, or add a driver-specific feature bit. >> >> Signed-off-by: Michael S. Tsirkin >> Signed-off-by: Jason Wang > The new VRING_DESC_F_URGENT bit is theoretically nicer, but for > networking (which tends to take packets in order) couldn't we just set > the event counter to give us a tx interrupt at the packet we want? > > Cheers, > Rusty. Yes, we could. Recent RFC of enabling tx interrupt use this.