Re: [kvm-unit-tests PATCH v3 4/5] configure: Add --qemu-cpu option

[Andrew Jones <andrew.jones@linux.dev>]

On Tue, Mar 25, 2025 at 04:00:32PM +0000, Jean-Philippe Brucker wrote:
> Add the --qemu-cpu option to let users set the CPU type to run on.
> At the moment --processor allows to set both GCC -mcpu flag and QEMU
> -cpu. On Arm we'd like to pass `-cpu max` to QEMU in order to enable all
> the TCG features by default, and it could also be nice to let users
> modify the CPU capabilities by setting extra -cpu options.  Since GCC
> -mcpu doesn't accept "max" or "host", separate the compiler and QEMU
> arguments.
> 
> `--processor` is now exclusively for compiler options, as indicated by
> its documentation ("processor to compile for"). So use $QEMU_CPU on
> RISC-V as well.
> 
> Suggested-by: Andrew Jones <andrew.jones@linux.dev>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---
>  scripts/mkstandalone.sh |  3 ++-
>  arm/run                 | 15 +++++++++------
>  riscv/run               |  8 ++++----
>  configure               | 24 ++++++++++++++++++++++++
>  4 files changed, 39 insertions(+), 11 deletions(-)
> 
> diff --git a/scripts/mkstandalone.sh b/scripts/mkstandalone.sh
> index 2318a85f..9b4f983d 100755
> --- a/scripts/mkstandalone.sh
> +++ b/scripts/mkstandalone.sh
> @@ -42,7 +42,8 @@ generate_test ()
>  
>  	config_export ARCH
>  	config_export ARCH_NAME
> -	config_export PROCESSOR
> +	config_export QEMU_CPU
> +	config_export DEFAULT_QEMU_CPU
>  
>  	echo "echo BUILD_HEAD=$(cat build-head)"
>  
> diff --git a/arm/run b/arm/run
> index efdd44ce..4675398f 100755
> --- a/arm/run
> +++ b/arm/run
> @@ -8,7 +8,7 @@ if [ -z "$KUT_STANDALONE" ]; then
>  	source config.mak
>  	source scripts/arch-run.bash
>  fi
> -processor="$PROCESSOR"
> +qemu_cpu="$QEMU_CPU"
>  
>  if [ "$QEMU" ] && [ -z "$ACCEL" ] &&
>     [ "$HOST" = "aarch64" ] && [ "$ARCH" = "arm" ] &&
> @@ -37,12 +37,15 @@ if [ "$ACCEL" = "kvm" ]; then
>  	fi
>  fi
>  
> -if [ "$ACCEL" = "kvm" ] || [ "$ACCEL" = "hvf" ]; then
> -	if [ "$HOST" = "aarch64" ] || [ "$HOST" = "arm" ]; then
> -		processor="host"
> +if [ -z "$qemu_cpu" ]; then
> +	if ( [ "$ACCEL" = "kvm" ] || [ "$ACCEL" = "hvf" ] ) &&
> +	   ( [ "$HOST" = "aarch64" ] || [ "$HOST" = "arm" ] ); then
> +		qemu_cpu="host"
>  		if [ "$ARCH" = "arm" ] && [ "$HOST" = "aarch64" ]; then
> -			processor+=",aarch64=off"
> +			qemu_cpu+=",aarch64=off"
>  		fi
> +	else
> +		qemu_cpu="$DEFAULT_QEMU_CPU"
>  	fi
>  fi
>  
> @@ -71,7 +74,7 @@ if $qemu $M -device '?' | grep -q pci-testdev; then
>  fi
>  
>  A="-accel $ACCEL$ACCEL_PROPS"
> -command="$qemu -nodefaults $M $A -cpu $processor $chr_testdev $pci_testdev"
> +command="$qemu -nodefaults $M $A -cpu $qemu_cpu $chr_testdev $pci_testdev"
>  command+=" -display none -serial stdio"
>  command="$(migration_cmd) $(timeout_cmd) $command"
>  
> diff --git a/riscv/run b/riscv/run
> index e2f5a922..02fcf0c0 100755
> --- a/riscv/run
> +++ b/riscv/run
> @@ -11,12 +11,12 @@ fi
>  
>  # Allow user overrides of some config.mak variables
>  mach=$MACHINE_OVERRIDE
> -processor=$PROCESSOR_OVERRIDE
> +qemu_cpu=$QEMU_CPU_OVERRIDE
>  firmware=$FIRMWARE_OVERRIDE
>  
> -[ "$PROCESSOR" = "$ARCH" ] && PROCESSOR="max"
> +[ -z "$QEMU_CPU" ] && QEMU_CPU="max"
>  : "${mach:=virt}"
> -: "${processor:=$PROCESSOR}"
> +: "${qemu_cpu:=$QEMU_CPU}"
>  : "${firmware:=$FIRMWARE}"
>  [ "$firmware" ] && firmware="-bios $firmware"
>  
> @@ -32,7 +32,7 @@ fi
>  mach="-machine $mach"
>  
>  command="$qemu -nodefaults -nographic -serial mon:stdio"
> -command+=" $mach $acc $firmware -cpu $processor "
> +command+=" $mach $acc $firmware -cpu $qemu_cpu "
>  command="$(migration_cmd) $(timeout_cmd) $command"
>  
>  if [ "$UEFI_SHELL_RUN" = "y" ]; then
> diff --git a/configure b/configure
> index b4875ef3..b79145a5 100755
> --- a/configure
> +++ b/configure
> @@ -23,6 +23,21 @@ function get_default_processor()
>      esac
>  }
>  
> +# Return the default CPU type to run on
> +function get_default_qemu_cpu()
> +{
> +    local arch="$1"
> +
> +    case "$arch" in
> +    "arm")
> +        echo "cortex-a15"
> +        ;;
> +    "arm64")
> +        echo "cortex-a57"
> +        ;;
> +    esac
> +}
> +
>  srcdir=$(cd "$(dirname "$0")"; pwd)
>  prefix=/usr/local
>  cc=gcc
> @@ -52,6 +67,7 @@ earlycon=
>  console=
>  efi=
>  efi_direct=
> +qemu_cpu=
>  
>  # Enable -Werror by default for git repositories only (i.e. developer builds)
>  if [ -e "$srcdir"/.git ]; then
> @@ -70,6 +86,9 @@ usage() {
>  	    --arch=ARCH            architecture to compile for ($arch). ARCH can be one of:
>  	                           arm, arm64, i386, ppc64, riscv32, riscv64, s390x, x86_64
>  	    --processor=PROCESSOR  processor to compile for ($processor)
> +	    --qemu-cpu=CPU         the CPU model to run on. If left unset, the run script
> +	                           selects the best value based on the host system and the
> +	                           test configuration.

I'm starting to think we should name this '--target-cpu'. We already have
'--target' which allows us to change the target to kvmtool and we may
support other emulators/vmms someday. riscv kvmtool is already gaining
support for different cpu types[1] and other vmms we add may have that
support as well. There's no reason to add a separate configure command
line option for each.

So let's rename QEMU_CPU to TARGET_CPU, but keep DEFAULT_QEMU_CPU as it
is, since that's qemu specific. run scripts will need to check TARGET
is "qemu" to decide if it should use DEFAULT_QEMU_CPU when TARGET_CPU
isn't set. Since TARGET is currently arm-only we can drop the riscv
changes from this patch. I can do them with a follow-on series.

[1] https://lore.kernel.org/all/20250326065644.73765-1-apatel@ventanamicro.com/

Thanks,
drew

>  	    --target=TARGET        target platform that the tests will be running on (qemu or
>  	                           kvmtool, default is qemu) (arm/arm64 only)
>  	    --cross-prefix=PREFIX  cross compiler prefix
> @@ -146,6 +165,9 @@ while [[ $optno -le $argc ]]; do
>          --processor)
>  	    processor="$arg"
>  	    ;;
> +	--qemu-cpu)
> +	    qemu_cpu="$arg"
> +	    ;;
>  	--target)
>  	    target="$arg"
>  	    ;;
> @@ -471,6 +493,8 @@ ARCH=$arch
>  ARCH_NAME=$arch_name
>  ARCH_LIBDIR=$arch_libdir
>  PROCESSOR=$processor
> +QEMU_CPU=$qemu_cpu
> +DEFAULT_QEMU_CPU=$(get_default_qemu_cpu $arch)
>  CC=$cc
>  CFLAGS=$cflags
>  LD=$cross_prefix$ld
> -- 
> 2.49.0
> 
> 
> -- 
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