Re: [PATCH 2/2] kunit: enable hardware acceleration when available

On 2024-11-01 10:49:36-0400, Tamir Duberstein wrote:

On Fri, Nov 1, 2024, 09:52 Alyssa Ross hi@alyssa.is wrote:

...

On Fri, Oct 25, 2024 at 05:03:54PM -0400, Tamir Duberstein wrote:

...

@@ -124,6 +125,29 @@ class LinuxSourceTreeOperationsQemu(LinuxSourceTreeOperations): '-no-reboot', '-nographic', '-serial', self._serial] + self._extra_qemu_params

•         accelerators = {
  

•                 line.strip()
  

•                 for line in subprocess.check_output([qemu_binary, "-accel", "help"], text=True).splitlines()
  

•                 if line and line.islower()
  

•         }
  

•         if 'kvm' in accelerators:
  

•                 try:
  

•                         with open('/dev/kvm', 'rb+'):
  

•                                 qemu_command.extend(['-accel', 'kvm'])
  

•                 except OSError as e:
  

•                         print(e)
  

•         elif 'hvf' in accelerators:
  

•                 try:
  

•                         for line in subprocess.check_output(['sysctl', 'kern.hv_support'], text=True).splitlines():
  

•                                 if not line:
  

•                                         continue
  

•                                 key, value = line.split(':')
  

•                                 if key == 'kern.hv_support' and bool(value):
  

•                                         qemu_command.extend(['-accel', 'hvf'])
  

•                                         break
  

•                 except subprocess.CalledProcessError as e:
  

•                         print(e)
  

QEMU supports falling back if one accelerator is not available, if you specify multiple like -accel kvm:tcg. Couldn't you rely on that rather than re-implementing the availability checks here?

Have you ever used that? Here's what I get when I try:

tamird@Tamirs-MacBook-Pro linux % tools/testing/kunit/kunit.py run --arch arm64 --make_options LLVM=1 --raw_output=all [10:45:03] Configuring KUnit Kernel ... [10:45:03] Building KUnit Kernel ... Populating config with: $ make ARCH=arm64 O=.kunit olddefconfig LLVM=1 Building with: $ make all compile_commands.json ARCH=arm64 O=.kunit --jobs=12 LLVM=1 [10:45:07] Starting KUnit Kernel (1/1)... Running tests with: $ qemu-system-aarch64 -nodefaults -m 1024 -kernel .kunit/arch/arm64/boot/Image.gz -append 'kunit.enable=1 console=ttyAMA0 kunit_shutdown=reboot' -no-reboot -nographic -serial stdio -accel kvm:tcg -machine virt -cpu max qemu-system-aarch64: -accel kvm:tcg: invalid accelerator kvm:tcg

The same thing happens with hvf:kvm:tcg or just hvf:tcg.

That syntax is for -machine accel=hvf:kvm:tcg. But you can also specify -accel multiple times.

I also can't find this in the documentation.

-accel name[,prop=value[,...]] This is used to enable an accelerator. [..] If there is more than one accelerator specified, the next one is used if the previous one fails to initialize.

-machine [type=]name[,prop=value[,...]] Supported machine properties are:

accel=accels1[:accels2[:...]] [..] If there is more than one accelerator specified, the next one is used if the previous one fails to initialize.

Thomas