On Mon, 2007-08-27 at 20:36 +0300, Avi Kivity wrote: > Anthony Liguori wrote: > > On Mon, 2007-08-27 at 19:47 +0300, Avi Kivity wrote: > > > >> Avi Kivity wrote: > >> > >>> Thinking a little more about this, it isn't about handling hypercalls > >>> in userspace, but about handling a virtio sync() in userspace. > >>> > >>> So how about having a KVM_HC_WAKE_CHANNEL hypercall (similar to Xen's > >>> event channel, but assymetric) that has a channel parameter. The > >>> kernel handler for that hypercall dispatches calls to either a kernel > >>> handler or a userspace handler. That means we don't need a separate > >>> ETH_SEND, ETH_RECEIVE, or BLOCK_SEND hypercalls. > >>> > >> And thinking a tiny little bit more about this, we can have the kernel > >> (optionally) fire an eventfd, so a separate userspace thread or process > >> can be woken up to service the device, without a heavyweight exit. > >> > > > > > > Yes, I think this is much nicer. By "calls to ... a userspace handler" > > I presume you mean generating an exit to userspace with a new exit type > > similar to how hypercalls work today? > > > > > > There are two options: > - hypercall handler sets some fields in vcpu->run and exits to userspace > - hypercall handler triggers an eventfd and returns to guest > > Maybe we can unify the two by only allowing eventfd;
Yes, that would be better except that the latency may be unacceptable. > userspace can > attach a signal to the eventfd if it wants a synchronous exit (does > eventfd allow fcntl(F_SETOWN)?) Which would address the latency issue nicely. Looking at the fs code, it looks like eventfd shouldn't have to do anything special for it. Regards, Anthony Liguori > ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ kvm-devel mailing list kvm-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/kvm-devel
