From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-6710-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 8003D985D19 for ; Tue, 11 Feb 2020 03:17:53 +0000 (UTC) References: <4c3d13be5a391b1fc50416838de57d903cbf8038.1581305609.git.zhabin@linux.alibaba.com> From: Jason Wang Message-ID: <0c71ff9d-1a7f-cfd2-e682-71b181bdeae4@redhat.com> Date: Tue, 11 Feb 2020 11:17:38 +0800 MIME-Version: 1.0 In-Reply-To: <4c3d13be5a391b1fc50416838de57d903cbf8038.1581305609.git.zhabin@linux.alibaba.com> Content-Language: en-US Subject: [virtio-dev] Re: [PATCH v2 4/5] virtio-mmio: add MSI interrupt feature support Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable To: Zha Bin , linux-kernel@vger.kernel.org Cc: virtio-dev@lists.oasis-open.org, slp@redhat.com, mst@redhat.com, jing2.liu@linux.intel.com, qemu-devel@nongnu.org, chao.p.peng@linux.intel.com, gerry@linux.alibaba.com List-ID: On 2020/2/10 =E4=B8=8B=E5=8D=885:05, Zha Bin wrote: > From: Liu Jiang > > Userspace VMMs (e.g. Qemu microvm, Firecracker) take advantage of using > virtio over mmio devices as a lightweight machine model for modern > cloud. The standard virtio over MMIO transport layer only supports one > legacy interrupt, which is much heavier than virtio over PCI transport > layer using MSI. Legacy interrupt has long work path and causes specific > VMExits in following cases, which would considerably slow down the > performance: > > 1) read interrupt status register > 2) update interrupt status register > 3) write IOAPIC EOI register > > We proposed to add MSI support for virtio over MMIO via new feature > bit VIRTIO_F_MMIO_MSI[1] which increases the interrupt performance. > > With the VIRTIO_F_MMIO_MSI feature bit supported, the virtio-mmio MSI > uses msi_sharing[1] to indicate the event and vector mapping. > Bit 1 is 0: device uses non-sharing and fixed vector per event mapping. > Bit 1 is 1: device uses sharing mode and dynamic mapping. I believe dynamic mapping should cover the case of fixed vector? Thanks --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org