qemu: set default RAM to 256M for all machines

There was a discussion about what amount of RAM is appropriate for a
default; the outcome was that for now it is still 256M. Some qemu machine
definitions have however set this to 512M so for the sake of
treating all architectures fairly, they are reset back to 256M.

Also runqemu is adjusted to use 256M if QB_MEM is not set at all.

http://lists.openembedded.org/pipermail/openembedded-core/2019-August/285900.html

(From OE-Core rev: 04c01b6cc5be3e6d45d0e04571640648a5655a8b)

Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/conf/machine/include/qemuboot-mips.inc

@@ -1,6 +1,5 @@
 # For runqemu
 IMAGE_CLASSES += "qemuboot"
-QB_MEM = "-m 256"
 QB_MACHINE = "-machine malta"
 QB_KERNEL_CMDLINE_APPEND = "console=ttyS0 console=tty"
 QB_OPT_APPEND = "-vga cirrus -show-cursor -usb -device usb-tablet"

meta/conf/machine/include/riscv/qemuriscv.inc

@@ -24,7 +24,6 @@ UBOOT_ENTRYPOINT_riscv64 = "0x80200000"
 
 # qemuboot options
 QB_KERNEL_CMDLINE_APPEND = "earlycon=sbi"
-QB_MEM = "-m 512"
 QB_MACHINE = "-machine virt"
 QB_DEFAULT_BIOS = "fw_jump.elf"
 QB_TAP_OPT = "-netdev tap,id=net0,ifname=@TAP@,script=no,downscript=no"

meta/conf/machine/qemuarm.conf

@@ -11,7 +11,6 @@ SERIAL_CONSOLES ?= "115200;ttyAMA0 115200;hvc0"
 
 # For runqemu
 QB_SYSTEM_NAME = "qemu-system-arm"
-QB_MEM = "-m 512"
 QB_MACHINE = "-machine virt"
 QB_CPU = "-cpu cortex-a15"
 # Standard Serial console

meta/conf/machine/qemuarm64.conf

@@ -11,7 +11,6 @@ SERIAL_CONSOLES ?= "115200;ttyAMA0 115200;hvc0"
 
 # For runqemu
 QB_SYSTEM_NAME = "qemu-system-aarch64"
-QB_MEM = "-m 512"
 QB_MACHINE = "-machine virt"
 QB_CPU = "-cpu cortex-a57"
 QB_CPU_KVM = "-cpu host"

scripts/runqemu

@@ -755,8 +755,8 @@ class BaseConfig(object):
         if s:
             self.set('QB_MEM', '-m %s' % s.group(1))
         elif not self.get('QB_MEM'):
-            logger.info('QB_MEM is not set, use 512M by default')
-            self.set('QB_MEM', '-m 512')
+            logger.info('QB_MEM is not set, use 256M by default')
+            self.set('QB_MEM', '-m 256')
 
         # Check and remove M or m suffix
         qb_mem = self.get('QB_MEM')