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 <john.liuli@xxxxxxxxxx> 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? Thank you in advance Best Regards Eric > > Li. >> . >> > > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
