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

Andrew Jones
2025-03-27T08:25:46Z

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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