On Tue, Jun 12, 2007 at 03:34:04PM +0100, Richard W.M. Jones wrote:

In xen_internal.c we've got code which claims to sniff out whether we are using new-style hypercall ioctls or old-style hypercall ioctls.

hc.op = __HYPERVISOR_xen_version; hc.arg[0] = (unsigned long) XENVER_version; hc.arg[1] = 0;

cmd = IOCTL_PRIVCMD_HYPERCALL; ret = ioctl(fd, cmd, (unsigned long) &hc);

if ((ret != -1) && (ret != 0)) { #ifdef DEBUG fprintf(stderr, "Using new hypervisor call: %X\n", ret); #endif hv_version = ret; xen_ioctl_hypercall_cmd = cmd; goto detect_v2; }

/* * check if the old hypercall are actually working */ v0_hc.op = __HYPERVISOR_xen_version; v0_hc.arg[0] = (unsigned long) XENVER_version; v0_hc.arg[1] = 0; cmd = _IOC(_IOC_NONE, 'P', 0, sizeof(v0_hypercall_t)); ret = ioctl(fd, cmd, (unsigned long) &v0_hc);

But on 64 bit platforms (not 32 bit) cmd will be identical, so we'll just be trying the same ioctl twice.

From <xen/linux/privcmd.h>:

typedef struct privcmd_hypercall { __u64 op; __u64 arg[5]; } privcmd_hypercall_t;

#define IOCTL_PRIVCMD_HYPERCALL \ _IOC(_IOC_NONE, 'P', 0, sizeof(privcmd_hypercall_t))

From src/xen_internal.c:

typedef struct v0_hypercall_struct { unsigned long op; unsigned long arg[5]; } v0_hypercall_t;

cmd = _IOC(_IOC_NONE, 'P', 0, sizeof(v0_hypercall_t));

On 64 bit platforms, both structures will be the same size.

yes but I prefer doing an extra hypercall once at the library init than trying to dig out whether on that particuliar box the structure will be the same or not. Daniel -- Red Hat Virtualization group http://redhat.com/virtualization/ Daniel Veillard | virtualization library http://libvirt.org/ veillard@redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/ http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/