boot-qemu.py: Allow memory value to be customized

The default memory value for most machines is 512 MB, which is generally
sufficient for most use cases, as these machines are usually quick to
start up and shutdown. Unfortunately, there are times where the machine
may run out of memory when percpu memory allocations are involved along
with a large number of cores, which can happen when booting under KVM
due to the script's heuristics for selecting a good default for '-smp',
which depends on the number of cores on the host machine.

Rather than try to adjust the existing heuristics further, allow users
to specify a memory value that may be better suited for their machine,
just like '-smp'.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Author: nathanchance

boot-qemu.py

@@ -49,6 +49,7 @@ def __init__(self):
         self.interactive = False
         self.kernel = None
         self.kernel_dir = None
+        self.memory = '512m'
         self.supports_efi = False
         # It may be tempting to use self.use_kvm during initialization of
         # subclasses to set certain properties but the user can explicitly opt
@@ -70,7 +71,6 @@ def __init__(self):
             '-nodefaults',
         ]  # yapf: disable
         self._qemu_path = None
-        self._ram = '512m'
 
     def _find_dtb(self):
         if not self._dtbs:
@@ -301,7 +301,7 @@ def run(self):
             self._qemu_args += ['-cpu', ','.join(self._kvm_cpu), '-enable-kvm']
 
         # Machine specs
-        self._qemu_args += ['-m', self._ram]
+        self._qemu_args += ['-m', self.memory]
         if self.smp:
             self._qemu_args += ['-smp', str(self.smp)]
 
@@ -512,7 +512,7 @@ def __init__(self):
             '-bios', bios,
             '-no-reboot',
         ]  # yapf: disable
-        self._ram = '2G'
+        self.memory = '2G'
         self.smp = 2
 
 
@@ -555,12 +555,12 @@ def __init__(self):
         super().__init__()
 
         self.cmdline.append('console=ttyS0')
+        self.memory = '128m'
         self._default_kernel_path = Path('arch/powerpc/boot/uImage')
         self._initrd_arch = 'ppc32'
         self._machine = 'bamboo'
         self._qemu_arch = 'ppc'
         self._qemu_args.append('-no-reboot')
-        self._ram = '128m'
 
     def run(self):
         self._qemu_args += ['-machine', self._machine]
@@ -582,21 +582,22 @@ class PowerPC64QEMURunner(QEMURunner):
     def __init__(self):
         super().__init__()
 
+        self.memory = '1G'
         self._default_kernel_path = Path('vmlinux')
         self._initrd_arch = self._qemu_arch = 'ppc64'
         self._qemu_args += [
             '-cpu', 'power8',
             '-machine', 'pseries',
             '-vga', 'none',
         ]  # yapf: disable
-        self._ram = '1G'
 
 
 class PowerPC64LEQEMURunner(QEMURunner):
 
     def __init__(self):
         super().__init__()
 
+        self.memory = '2G'
         self._default_kernel_path = Path('arch/powerpc/boot/zImage.epapr')
         self._initrd_arch = 'ppc64le'
         self._qemu_arch = 'ppc64'
@@ -605,7 +606,6 @@ def __init__(self):
             '-device', 'isa-ipmi-bt,bmc=bmc0,irq=10',
             '-machine', 'powernv',
         ]  # yapf: disable
-        self._ram = '2G'
 
 
 class RISCVQEMURunner(QEMURunner):
@@ -811,6 +811,12 @@ def parse_arguments():
         '--shell',
         action='store_true',
         help='Instead of immediately shutting down machine, spawn a shell.')
+    parser.add_argument(
+        '-m',
+        '--memory',
+        help=
+        "Value for '-m' QEMU option (default: generally '512m', depends on machine)",
+    )
     parser.add_argument(
         '-s',
         '--smp',
@@ -884,6 +890,9 @@ def parse_arguments():
     if args.gh_json_file:
         runner.gh_json_file = Path(args.gh_json_file).resolve()
 
+    if args.memory:
+        runner.memory = args.memory
+
     if args.no_kvm:
         runner.use_kvm = False