On 07.03.25 17:49, Philippe Mathieu-Daudé wrote:
On 7/3/25 17:38, Alex Bennée wrote:
Philippe Mathieu-Daudé <[email protected]> writes:
Use qemu_arch_available() to check at runtime if a target
architecture is built in.
Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
---
hw/virtio/virtio-mem.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)
diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
index 5f57eccbb66..8c40042108c 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 +171,16 @@ 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)
+{
+ if (qemu_arch_available(QEMU_ARCH_I386 | QEMU_ARCH_S390X)) {
+ return 2 * 128 * MiB;
+ } else if (qemu_arch_available(QEMU_ARCH_ARM)) {
+ return 2 * 512 * MiB;
+ } else {
+ g_assert_not_reached();
+ }
+}
What happens if/when we have multiple arches available? Won't we want to
know which CPU the virtio-mem device is attached to or do we take the
minimal value over the whole system?
We should take the maximum value here, not the minimum.
"per attached vcpu" is how I was previously considering this problem,
but IIUC from the discussions with Pierrick, we should consider single
binary as a first step before heterogeneous emulation.
It would be related to the machine/vcpu, yes.
Taking the maximum over all available arches is easier; it's a pure
optimization.
--
Cheers,
David / dhildenb
