From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shannon Zhao Subject: Re: [Qemu-devel] [RFC PATCH 0/2] virtio-mmio: add irqfd support for vhost-net based on virtio-mmio Date: Thu, 6 Nov 2014 09:59:24 +0800 Message-ID: <545AD5FC.1030600__16804.6661805876$1415631813$gmane$org@huawei.com> References: <1414225494-2208-1-git-send-email-john.liuli@huawei.com> <544E2B18.8010702@huawei.com> <5459E343.6030907@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5459E343.6030907@linaro.org> 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 To: Eric Auger , Li Liu , Peter Maydell Cc: Joel Schopp , "eric.auger@st.com" , Yingshiuan Pan , "Michael S. Tsirkin" , remy.gauguey@cea.fr, lkml - Kernel Mailing List , Nikolay Nikolaev , QEMU Developers , peter.huangpeng@huawei.com, "virtualization@lists.linux-foundation.org" , Christoffer Dall List-Id: virtualization@lists.linuxfoundation.org On 2014/11/5 16:43, Eric Auger wrote: > On 10/27/2014 12:23 PM, Li Liu wrote: >> >> >> On 2014/10/27 17:37, Peter Maydell wrote: >>> On 25 October 2014 09:24, john.liuli wrote: >>>> To get the interrupt reason to support such VIRTIO_NET_F_STATUS >>>> features I add a new register offset VIRTIO_MMIO_ISRMEM which >>>> will help to establish a shared memory region between qemu and >>>> virtio-mmio device. Then the interrupt reason can be accessed by >>>> guest driver through this region. At the same time, the virtio-mmio >>>> dirver check this region to see irqfd is supported or not during >>>> the irq handler registration, and different handler will be assigned. >>> >>> If you want to add a new register you should probably propose >>> an update to the virtio spec. However, it seems to me it would >>> be better to get generic PCI/PCIe working on the ARM virt >>> board instead; then we can let virtio-mmio quietly fade away. >>> This has been on the todo list for ages (and there have been >>> RFC patches posted for plain PCI), it's just nobody's had time >>> to work on it. >>> >>> thanks >>> -- PMM >>> >> >> So you mean virtio-mmio will be replaced by PCI/PCIe on ARM at last? >> If so, let this patch go with the wind:). Thx. > > Hi, > > As a fix of current situation where ISR is only partially updated when > vhost-irqfd handles standard IRQ and waiting for PCI emuluation, > wouldn't it make sense to store ISR content on vhost driver side and > introduce ioctls to read/write it. When using vhost BE, virtio QEMU > device would use those ioctl to read/update the ISR content. On top of > that we would update the ISR in vhost before triggering the irqfd. If I > do not miss anything this would at least make things functional with irqfd. > > As a second step, we could try to introduce in-kernel emulation of > ISR/ACK to fix the performance issue related to going to user-side each > time ISR/ACK accesses are done. > > Do you think it is worth investigating this direction? > Hi, About this problem I have a talk with Li Liu. As MST said, we could use multiple GSI to support vhost-net with irqfd. And we have figured out a way to solve this problem. The method is as same as virtio-pci which is to assign multiple irqs for virtio-mmio. Also it can support multiqueue virtio-net on arm. Would you have a look at this method? Thank you very much. - virtio-mmio: support for multiple irqs http://www.spinics.net/lists/kernel/msg1858860.html Thanks, Shannon > Thank you in advance > > Best Regards > > Eric > > >> >> Li. >>> . >>>