While qemu definitely caps granularity to 64 MiB, it places no limits on buf-size. On a machine beefy enough for lots of memory, a buf-size larger than 2 GiB is feasible, so we should pass a 64-bit parameter. * include/libvirt/libvirt.h.in (VIR_DOMAIN_BLOCK_COPY_BUF_SIZE): Allow 64 bits. Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- Based on Peter's review of my patch series; until we have an implementation, it is just a doc bug, but I'd rather document it correctly and avoid baking in a too-small API. include/libvirt/libvirt.h.in | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in index e79c9ad..e80634e 100644 --- a/include/libvirt/libvirt.h.in +++ b/include/libvirt/libvirt.h.in @@ -2663,8 +2663,8 @@ typedef enum { * VIR_DOMAIN_BLOCK_COPY_BUF_SIZE: * Macro for the virDomainBlockCopy buffer size tunable: it represents * how much data in bytes can be in flight between source and destination, - * as an unsigned int. Specifying 0 is the same as omitting this parameter, - * to request the hypervisor default. + * as an unsigned long long. Specifying 0 is the same as omitting this + * parameter, to request the hypervisor default. */ #define VIR_DOMAIN_BLOCK_COPY_BUF_SIZE "buf-size" -- 1.9.3