Re: [Libvir] Bug in the virDomainGetInfo() API of libvirt 0.1.9 with Xen 3.0.3

On Fri, Jan 12, 2007 at 03:04:57PM +0100, Philippe Berthault wrote: > Daniel Veillard a écrit : > > I think Xen just returns -1 when the field is uninitialized, probably > >meaning 'all physical memory'. Once you use "xm mem-max 0 ..." then it > >consider the Dom0 domain constrained, but not before. And since there > >are machine where it's possible to hot plug new memory this is a way to > >not poll the current physical memory, a bit weird but that can be > >understood. > > > The signed value -1, "casted" in C/C++ in unsigned integer, gives the > value 4294967295. The Max memory value returned by virsh is 4294967292. > There is a small difference (3), so the value returned by Xen can't be -1. You're forgetting though, that xen measures this in terms of pages. Libvirt converts that to bytes. The virsh converts it to KB when printing it. $cat > demo.c <<EOF #include <stdio.h> int main() { unsigned int max_pages = ~0U; unsigned long long mem = (unsigned long long)max_pages * 4096ull; unsigned long memkb = mem / 1024; printf("%u %llu %lu\n", max_pages, mem, memkb); } EOF $ gcc -o demo demo.c $ ./demo 4294967295 17592186040320 4294967292