Messages in this thread | | | Subject | Re: [PATCH v2 4/5] virtio-mmio: add MSI interrupt feature support | From | Jason Wang <> | Date | Tue, 11 Feb 2020 11:17:38 +0800 |
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On 2020/2/10 下午5:05, Zha Bin wrote: > From: Liu Jiang<gerry@linux.alibaba.com> > > 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
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