qemuDomainBlockCopy: Check @granularity to be a power of two

https://bugzilla.redhat.com/show_bug.cgi?id=1206479

As described in virDomainBlockCopy() parameters description, the
VIR_DOMAIN_BLOCK_COPY_GRANULARITY parameter may require the value to
have some specific attributes (e.g. be a power of two or fall within a
certain range). And in qemu, a power of two is required. However, our
code does not check that and let qemu operation fail. Moreover, the
virsh man page is not as exact as it could be in this respect.
Signed-off-by: NLuyao Huang <lhuang@redhat.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_driver.c

@@ -16866,6 +16866,11 @@ qemuDomainBlockCopy(virDomainPtr dom, const char *disk, const char *destxml,
             }
             bandwidth = param->value.ul;
         } else if (STREQ(param->field, VIR_DOMAIN_BLOCK_COPY_GRANULARITY)) {
+            if (param->value.ui != VIR_ROUND_UP_POWER_OF_TWO(param->value.ui)) {
+                virReportError(VIR_ERR_INVALID_ARG, "%s",
+                               _("granularity must be power of 2"));
+                goto cleanup;
+            }
             granularity = param->value.ui;
         } else if (STREQ(param->field, VIR_DOMAIN_BLOCK_COPY_BUF_SIZE)) {
             buf_size = param->value.ul;

tools/virsh.pod

@@ -1039,10 +1039,10 @@ unlimited, but more likely would overflow; it is safer to use 0 for that
 purpose.  Specifying I<granularity> allows fine-tuning of the granularity that
 will be copied when a dirty region is detected; larger values trigger less
 I/O overhead but may end up copying more data overall (the default value is
-usually correct); this value must be a power of two.  Specifying I<buf-size>
-will control how much data can be simultaneously in-flight during the copy;
-larger values use more memory but may allow faster completion (the default
-value is usually correct).
+usually correct); hypervisors may restrict this to be a power of two or fall
+within a certain range. Specifying I<buf-size> will control how much data can
+be simultaneously in-flight during the copy; larger values use more memory but
+may allow faster completion (the default value is usually correct).
 
 =item B<blockpull> I<domain> I<path> [I<bandwidth>] [I<base>]
 [I<--wait> [I<--verbose>] [I<--timeout> B<seconds>] [I<--async>]]