Re: [Xen-devel] interdomain event channel using libxc

[Francesco Tamberi <francesco.tamberi@xxxxxxxxx>]

Hi,

This stub works well for me, but suppose I have to "move" the domU code at
"kernel level" (i.e. as a module) which hypercalls should I invoke and in
what order?

This is a "stupid" scheme of what I mean to do:
domU --> kernel level, using hypercalls
dom0 --> user level (see code below), using libxc

Thanks

-- f


Stephan Creutz wrote:
> 
> Hi,
> 
> [... cut]
> 
> Program running in Dom0:
> 
> #include <stdio.h>
> #include <time.h>
> #include <sys/select.h>
> #include <xen/xenctrl.h>
> 
> static int xc_handle = -1;
> 
> static void event_channel(uint32_t domid)
> {
>       int xce_handle = xc_evtchn_open();
>       if (xce_handle == -1) {
>               fprintf(stderr, "opening event channel failed\n");
>               return;
>       }
>       
>       int port = xc_evtchn_alloc_unbound(xc_handle, DOMID_SELF, domid);
>       if (port == -1)
>               fprintf(stderr, "port allocation failed\n");
>       else
>               printf("allocated port: %d\n", port);
> 
>       fd_set rfds;
> 
>       FD_ZERO(&rfds);
>       int evtchn_fd = xc_evtchn_fd(xce_handle);
>       FD_SET(evtchn_fd, &rfds);
> 
>       struct timeval select_timeout = {
>               .tv_sec = 10,
>               .tv_usec = 0
>       };
>       
>       if (xc_evtchn_unmask(xce_handle, (evtchn_port_t)port) == -1)
>               fprintf(stderr, "unmasking failed\n");
> 
>       printf(">>> select\n");
>       int ret = select(evtchn_fd + 1, &rfds, NULL, NULL, &select_timeout);
> 
>       if (ret == -1)
>               perror("select()");
>       else if (ret && FD_ISSET(evtchn_fd, &rfds)) {
>               printf(">>> event <<<\n");
>               evtchn_port_t next_port;
>               if ((next_port = xc_evtchn_pending(xce_handle)) ==
>                               (evtchn_port_t)-1)
>                       perror("xc_evtchn_pending");
>               if (xc_evtchn_unmask(xce_handle, next_port) == -1)
>                       fprintf(stderr, "unable to umask\n");
>       } else
>               fprintf(stderr, "select timeout\n");
> 
>       xc_evtchn_close(xce_handle);
>       printf("eventchannel closed\n");
> }
> 
> int main(void)
> {
>       xc_handle = xc_interface_open();
>       if (xc_handle == -1) {
>               fprintf(stderr, "connection to hypervisor failed\n");
>               return 1;
>       }
> 
>       xc_dominfo_t dominfo[2];
>       int number_of_domains = xc_domain_getinfo(xc_handle, 0, 2, dominfo);
>       if (number_of_domains < 2) {
>               fprintf(stderr, "there is only one domain, but need two\n");
>               goto error;
>       }
> 
>       event_channel(dominfo[1].domid);
> 
> error:
>       xc_interface_close(xc_handle);
>       return 0;
> }
> 
> Program running in DomU:
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <time.h>
> #include <xen/xenctrl.h>
> 
> static int xc_handle = -1;
> static const uint32_t domid = 0;
> 
> int main(int argc, char **argv)
> {
>       if (argc < 2) {
>               fprintf(stderr, "usage: %s <remote-port>\n", argv[0]);
>               return 1;
>       }
>       
>       xc_handle = xc_interface_open();
>       if (xc_handle == -1) {
>               fprintf(stderr, "connection to hypervisor failed\n");
>               return 1;
>       }
>       
>       int xce_handle = xc_evtchn_open();
>       if (xce_handle == -1) {
>               fprintf(stderr, "opening of event channel failed\n");
>               goto error;
>       }
>       
>       evtchn_port_t remote_port = (evtchn_port_t)atoi(argv[1]);
>       evtchn_port_t local_port;
>       local_port = xc_evtchn_bind_interdomain(xce_handle, domid,
> remote_port); if (local_port == (evtchn_port_t)-1)
>               fprintf(stderr, "binding to interdomain channel failed\n");
>       
>       if (xc_evtchn_notify(xce_handle, local_port) == -1)
>               fprintf(stderr, "notify failed\n");
>       
>       struct timespec nano_timespec = {
>               .tv_sec = 5,
>               .tv_nsec = 0
>       };
>       nanosleep(&nano_timespec, NULL);
>       if (xc_evtchn_unbind(xce_handle, local_port) == -1)
>               fprintf(stderr, "unbind failed\n");
>       xc_evtchn_close(xce_handle);
>       
> error:
>       xc_interface_close(xc_handle);
>       return 0;
> }
> 

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