test: extend test_max_devices to support aarch64

The test_max_devices test verifies the maximum number of devices that
can be attached, as permitted by the platform. It checks both that the
expected number of devices can be successfully attached and that
attaching more than the limit results in a failure.

Previously, this test was only executed on x86_64, where 18 devices are
expected. This update extends the test to run on aarch64 as well, which
supports up to 94 devices.

Signed-off-by: Sheng-Wei (Way) Chen <[email protected]>

Author: Swchexit

CHANGELOG.md

@@ -40,6 +40,9 @@ and this project adheres to
 - [#5260](https://github.com/firecracker-microvm/firecracker/pull/5260): Fixed a
   bug allowing the block device to starve all other devices when backed by a
   sufficiently slow drive.
+- [#4207](https://github.com/firecracker-microvm/firecracker/issues/4207): Fixed
+  GSI numbering on aarch64 to correctly allow up to 96 devices being attached
+  simultaneously.
 
 ## [1.12.0]
 

tests/integration_tests/functional/test_max_devices.py

@@ -6,14 +6,17 @@
 
 import pytest
 
-# IRQs are available from 5 to 23. We always use one IRQ for VMGenID device, so
-# the maximum number of devices supported at the same time is 18.
-MAX_DEVICES_ATTACHED = 18
+# On x86_64, IRQs are available from 5 to 23. We always use one IRQ for VMGenID
+# device, so the maximum number of devices supported at the same time is 18.
 
+# On aarch64, IRQs are available from 32 to 127. We always use one IRQ each for
+# the VMGenID and RTC devices, so the maximum number of devices supported
+# at the same time is 94.
+MAX_DEVICES_ATTACHED = {
+    "x86_64": 18,
+    "aarch64": 94
+}.get(platform.machine())
 
-@pytest.mark.skipif(
-    platform.machine() != "x86_64", reason="Firecracker supports 24 IRQs on x86_64."
-)
 def test_attach_maximum_devices(uvm_plain_any):
     """
     Test attaching maximum number of devices to the microVM.
@@ -36,9 +39,6 @@ def test_attach_maximum_devices(uvm_plain_any):
         test_microvm.ssh_iface(i).check_output("sync")
 
 
-@pytest.mark.skipif(
-    platform.machine() != "x86_64", reason="Firecracker supports 24 IRQs on x86_64."
-)
 def test_attach_too_many_devices(uvm_plain):
     """
     Test attaching to a microVM more devices than available IRQs.