Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751598AbaKFJ0T (ORCPT ); Thu, 6 Nov 2014 04:26:19 -0500 Received: from [119.145.14.65] ([119.145.14.65]:18083 "EHLO szxga02-in.huawei.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751219AbaKFJ0Q (ORCPT ); Thu, 6 Nov 2014 04:26:16 -0500 Message-ID: <545B3E48.9020804@huawei.com> Date: Thu, 6 Nov 2014 17:24:24 +0800 From: Li Liu User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Shannon Zhao , Eric Auger , Peter Maydell CC: Joel Schopp , Yingshiuan Pan , "Michael S. Tsirkin" , , Rusty Russell , "lkml - Kernel Mailing List" , Nikolay Nikolaev , QEMU Developers , , "virtualization@lists.linux-foundation.org" , "eric.auger@st.com" , Christoffer Dall Subject: Re: [Qemu-devel] [RFC PATCH 0/2] virtio-mmio: add irqfd support for vhost-net based on virtio-mmio References: <1414225494-2208-1-git-send-email-john.liuli@huawei.com> <544E2B18.8010702@huawei.com> <5459E343.6030907@linaro.org> <545AD5FC.1030600@huawei.com> In-Reply-To: <545AD5FC.1030600@huawei.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.142.143.9] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014/11/6 9:59, Shannon Zhao wrote: > > > 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 > Yeah, I think multiple GSI is more compatible with MSI-X. And even virtio-mmio will fade away at last. It still make senses for ARM32 which can't support PCI/PCIe. BTW, this patch is handed over to Shannon and please refer to new patch at http://www.spinics.net/lists/kernel/msg1858860.html. Li. >> Thank you in advance >> >> Best Regards >> >> Eric >> >> >>> >>> Li. >>>> . >>>> > > > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/