Windows XP seems to have issues when _PRT() returns a variable package.
We know in advance the size, so we can return a fixed package instead.
https://lore.kernel.org/qemu-devel/c82d9331-a8ce-4bb0-b51f-2ee789e27c86@ilande.co.uk/T/#m541190c942676bccf7a7f7fbcb450d94a4e2da53

Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Fixes: 99cb2c6c7b ("hw/i386/acpi-build: Return a pre-computed _PRT table")
Closes: https://lore.kernel.org/all/eb11c984-ebe4-4a09-9d71-1e9db7fe7e6f@ilande.co.uk/
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 hw/i386/acpi-build.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 4967aa7459..d2be77199b 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -741,7 +741,8 @@ static Aml *build_prt(bool is_pci0_prt)
     int pin;
 
     method = aml_method("_PRT", 0, AML_NOTSERIALIZED);
-    rt_pkg = aml_varpackage(nroutes);
+    assert(nroutes < 256);
+    rt_pkg = aml_package(nroutes);
 
     for (pin = 0; pin < nroutes; pin++) {
         Aml *pkg = aml_package(4);
-- 
2.46.0.792.g87dc391469-goog