libqos: allow zero-size allocations

As part of streamlining the AHCI tests interface, it'd be nice
if specying a size of zero could be handled without special branches
and the allocator could handle this special case gracefully.

This lets me use the "ahci_io" macros for non-data commands, too,
which moves me forward towards shepherding all AHCI qtests into
a common set of commands in a unified pipeline.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 1452282920-21550-6-git-send-email-jsnow@redhat.com

2 files changed, 7 insertions, 3 deletions

diff --git a/tests/libqos/ahci.c b/tests/libqos/ahci.c
index 96a05a8599..6536408a7d 100644
--- a/tests/libqos/ahci.c
+++ b/tests/libqos/ahci.c
@@ -668,16 +668,16 @@ void ahci_io(AHCIQState *ahci, uint8_t port, uint8_t ide_cmd,
     props = ahci_command_find(ide_cmd);
     g_assert(props);
     ptr = ahci_alloc(ahci, bufsize);
-    g_assert(ptr);
+    g_assert(!bufsize || ptr);
     qmemset(ptr, 0x00, bufsize);
 
-    if (props->write) {
+    if (bufsize && props->write) {
         bufwrite(ptr, buffer, bufsize);
     }
 
     ahci_guest_io(ahci, port, ide_cmd, ptr, bufsize, sector);
 
-    if (props->read) {
+    if (bufsize && props->read) {
         bufread(ptr, buffer, bufsize);
     }
 
diff --git a/tests/libqos/malloc.c b/tests/libqos/malloc.c
index 82b9df537a..19d05cafa6 100644
--- a/tests/libqos/malloc.c
+++ b/tests/libqos/malloc.c
@@ -270,6 +270,10 @@ uint64_t guest_alloc(QGuestAllocator *allocator, size_t size)
     uint64_t rsize = size;
     uint64_t naddr;
 
+    if (!size) {
+        return 0;
+    }
+
     rsize += (allocator->page_size - 1);
     rsize &= -allocator->page_size;
     g_assert_cmpint((allocator->start + rsize), <=, allocator->end);