Re: [libvirt] [PATCH] Fix initialization of current vcpus in libxl driver

On 05/24/2011 10:33 AM, Jim Fehlig wrote: > This works in the libxl driver since cur_vcpus is an int. But > vcpu_avail is a long in xenxs/xen_sxpr.c and I'm hoping there is > something better than the following approach > > diff --git a/src/xenxs/xen_sxpr.c b/src/xenxs/xen_sxpr.c > index 4cebb21..dc000a8 100644 > --- a/src/xenxs/xen_sxpr.c > +++ b/src/xenxs/xen_sxpr.c > @@ -2006,9 +2006,14 @@ xenFormatSxpr(virConnectPtr conn, > virBufferAsprintf(&buf, "(vcpus %u)", def->maxvcpus); > /* Computing the vcpu_avail bitmask works because MAX_VIRT_CPUS is > either 32, or 64 on a platform where long is big enough. */ > - if (def->vcpus < def->maxvcpus) > - virBufferAsprintf(&buf, "(vcpu_avail %lu)", > - def->vcpus == 32 ? 1 << 31 : (1UL << > def->vcpus) - 1); > > + if (def->vcpus < def->maxvcpus) { > If def->maxvcpus is 32, then: > + if (sizeof(long) == 4 && def->vcpus == 32) > this conditional will never be reached (def->vcpus is less than def->maxvcpus). So the existing ((1UL << def->vcpus) -1) never calls the non-portable 1UL<<32 (or 1UL<<64); so it never overflows.