Re: [Libvir] PATCH: Fix compat for Xen 3.2.0

On Sat, Jan 19, 2008 at 09:21:07PM +0100, Jim Meyering wrote: > "Daniel P. Berrange" <berrange(a)redhat.com&gt; wrote: > >> Xen 3.2.0 removed the sockets_per_node field from the nodeinfo data returned >> by XenD. I previously add compat for this, but got it in the wrong place >> so it would most likely end up in a divide-by-zero error. This patch >> re-arranges it to be correct. >> >> diff -rup libvirt-0.4.0.orig/src/xend_internal.c libvirt-0.4.0.new/src/xend_internal.c >> --- libvirt-0.4.0.orig/src/xend_internal.c 2007-12-17 18:05:27.000000000 -0500 >> +++ libvirt-0.4.0.new/src/xend_internal.c 2008-01-18 21:13:30.000000000 -0500 >> @@ -1907,6 +1907,9 @@ sexpr_to_xend_node_info(struct sexpr *ro >> info->mhz = sexpr_int(root, "node/cpu_mhz"); >> info->nodes = sexpr_int(root, "node/nr_nodes"); >> info->sockets = sexpr_int(root, "node/sockets_per_node"); >> + info->cores = sexpr_int(root, "node/cores_per_socket"); >> + info->threads = sexpr_int(root, "node/threads_per_core"); >> + >> /* Xen 3.2.0 replaces sockets_per_node with 'nr_cpus'. >> * Old Xen calculated sockets_per_node using its internal >> * nr_cpus / (nodes*cores*threads), so fake it ourselves >> @@ -1921,8 +1924,6 @@ sexpr_to_xend_node_info(struct sexpr *ro >> if (info->sockets == 0) >> info->sockets = 1; >> } >> - info->cores = sexpr_int(root, "node/cores_per_socket"); >> - info->threads = sexpr_int(root, "node/threads_per_core"); >> return (0); >> } > ACK. > > Now that you mention divide-by-zero, > is there something that guarantees none of the > terms in the denominator there is zero? > > info->sockets = nr_cpus / (info->nodes * info->cores * info->threads); You always have at least 1 numa node, at least 1 core, and at least 1 hyperthread, so you'd only get a zero in those if there was a bug in the Xen hypervisor