On 22.08.23 11:45, Viresh Kumar wrote:
Xen provides support for injecting interrupts to the guests via the HYPERVISOR_dm_op() hypercall. The same is used by the Virtio based device backend implementations, in an inefficient manner currently.
Generally, the Virtio backends are implemented to work with the Eventfd based mechanism. In order to make such backends work with Xen, another software layer needs to poll the Eventfds and raise an interrupt to the guest using the Xen based mechanism. This results in an extra context switch.
This is not a new problem in Linux though. It is present with other hypervisors like KVM, etc. as well. The generic solution implemented in the kernel for them is to provide an IOCTL call to pass the interrupt details and eventfd, which lets the kernel take care of polling the eventfd and raising of the interrupt, instead of handling this in user space (which involves an extra context switch).
This patch adds support to inject a specific interrupt to guest using the eventfd mechanism, by preventing the extra context switch.
Inspired by existing implementations for KVM, etc..
Signed-off-by: Viresh Kumar viresh.kumar@linaro.org
Pushed to xen/tip.git for-linus-6.6
Juergen