[PATCH v2 5/7] hw/virtio/virtio-mem: Convert VIRTIO_MEM_USABLE_EXTENT to runtime

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Use qemu_arch_available() to check at runtime if a target
architecture is built in.

Consider the maximum extent size of any architecture built in.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/virtio/virtio-mem.c | 28 ++++++++++++++++++++--------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index 5f57eccbb66..6ff9dab0f66 100644
--- a/hw/virtio/virtio-mem.c
+++ b/hw/virtio/virtio-mem.c
@@ -15,6 +15,7 @@
 #include "qemu/cutils.h"
 #include "qemu/error-report.h"
 #include "qemu/units.h"
+#include "system/arch_init.h"
 #include "system/numa.h"
 #include "system/system.h"
 #include "system/reset.h"
@@ -170,13 +171,24 @@ static bool virtio_mem_has_shared_zeropage(RAMBlock *rb)
  * necessary (as the section size can change). But it's more likely that the
  * section size will rather get smaller and not bigger over time.
  */
-#if defined(TARGET_X86_64) || defined(TARGET_I386) || defined(TARGET_S390X)
-#define VIRTIO_MEM_USABLE_EXTENT (2 * (128 * MiB))
-#elif defined(TARGET_ARM)
-#define VIRTIO_MEM_USABLE_EXTENT (2 * (512 * MiB))
-#else
-#error VIRTIO_MEM_USABLE_EXTENT not defined
-#endif
+static uint64_t virtio_mem_usable_extent_size(void)
+{
+    uint64_t size = 0;
+
+    assert(qemu_arch_available(QEMU_ARCH_ARM | QEMU_ARCH_I386 | QEMU_ARCH_S390X));
+    /*
+     * FIXME: We should use the maximum of instantiated vCPUs ARCH, but
+     *        for now it is easier to take the maximum of any ARCH built in.
+     */
+    if (qemu_arch_available(QEMU_ARCH_I386 | QEMU_ARCH_S390X)) {
+        size = MAX(size, 2 * 128 * MiB);
+    }
+    if (qemu_arch_available(QEMU_ARCH_ARM)) {
+        size = MAX(size, 2 * 512 * MiB);
+    }
+
+    return size;
+}
 
 static bool virtio_mem_is_busy(void)
 {
@@ -721,7 +733,7 @@ static void virtio_mem_resize_usable_region(VirtIOMEM *vmem,
                                             bool can_shrink)
 {
     uint64_t newsize = MIN(memory_region_size(&vmem->memdev->mr),
-                           requested_size + VIRTIO_MEM_USABLE_EXTENT);
+                           requested_size + virtio_mem_usable_extent_size());
 
     /* The usable region size always has to be multiples of the block size. */
     newsize = QEMU_ALIGN_UP(newsize, vmem->block_size);
-- 
2.47.1