On Mon, Jul 29, 2024 at 2:03 PM Srivatsa Vaddagiri <quic_svaddagi@xxxxxxxxxxx> wrote: > > * Jason Wang <jasowang@xxxxxxxxxx> [2024-07-29 10:16:48]: > > > > Without this optimization, guest VCPU would have stalled until VMM in host can > > > emulate it, which can be long, especially a concern when the read is issued in > > > hot path (interrupt handler, w/o MSI_X). > > > > I think I agree with Michael, let's try to use MSI-X here where > > there's a lot of existing optimizations in various layers. > > Yes sure. Even if we implement MSI-X, there is a security angle to why we want > hypervisor-hosted PCI bus (have provided details in an earlier reply > > https://lore.kernel.org/virtio-dev/20240726070609.GB723942@xxxxxxxxxxx/T/#m84455763d6b4d0d3b8df814b3d64e6e48ec12ae3 > > > > > > > We will however likely need vduse to support configuration writes (guest VM > > > > > updating configuration space, for ex: writing to 'events_clear' field in case of > > > > > virtio-gpu). Would vduse maintainers be willing to accept config_write support > > > > > for select devices/features (as long as the writes don't violate any safety > > > > > concerns we may have)? > > > > > > > > I think so, looking at virtio_gpu_config_changed_work_func(), the > > > > events_clear seems to be fine to have a posted semantic. > > > > > > > > Maybe you can post an RFC to support config writing and let's start from there? > > Does VDUSE support runtime configuration changes (ex: block device capacity > changes)? Looks like it can, it has VDUSE_DEV_INJECT_CONFIG_IRQ. > I am curious how the atomicity of that update is handled. For ex: > guest reading config space while concurrent updates are underway (SET_CONFIG). > I think the generation count should help there - but it was not clear to me how > VDUSE is handling generation_count reads during such concurrent udpates. Similar to the above, we are missing uAPI to do that. Probably just an uAPI to update the device generation. Thanks > > - vatsa >
