Re: [kvm-unit-tests PATCH v3 13/16] scripts: Do not probe for maximum number of VCPUs when using kvmtool

Andrew Jones
2025-05-07T16:49:07Z

On Wed, May 07, 2025 at 04:12:53PM +0100, Alexandru Elisei wrote:
> The --probe-maxsmp parameter updates MAX_SMP with the maximum number of
> VCPUs that the host supports. Qemu will exit with an error when creating a
> virtual machine if the number of VCPUs is exceeded.
>
> kvmtool behaves differently: it will automatically limit the number of
> VCPUs to the what KVM supports, which is exactly what --probe-maxsmp wants
> to achieve. When doing --probe-maxsmp with kvmtool, print a message
> explaining why it's redundant and don't do anything else.
>
> Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com>
> ---
> run_tests.sh | 3 ++-
> scripts/runtime.bash | 16 ----------------
> scripts/vmm.bash | 24 ++++++++++++++++++++++++
> 3 files changed, 26 insertions(+), 17 deletions(-)
>
> diff --git a/run_tests.sh b/run_tests.sh
> index 150a06a91064..a69c3665b7a4 100755
> --- a/run_tests.sh
> +++ b/run_tests.sh
> @@ -10,6 +10,7 @@ if [ ! -f config.mak ]; then
> fi
> source config.mak
> source scripts/common.bash
> +source scripts/vmm.bash
>
> function usage()
> {
> @@ -90,7 +91,7 @@ while [ $# -gt 0 ]; do
> list_tests="yes"
> ;;
> --probe-maxsmp)
> - probe_maxsmp
> + ${vmm_opts[$TARGET:probe_maxsmp]}
> ;;
> --)
> ;;
> diff --git a/scripts/runtime.bash b/scripts/runtime.bash
> index 01ec8eae2bba..a802686c511d 100644
> --- a/scripts/runtime.bash
> +++ b/scripts/runtime.bash
> @@ -209,19 +209,3 @@ function run()
>
> return $ret
> }
> -
> -#
> -# Probe for MAX_SMP, in case it's less than the number of host cpus.
> -#
> -function probe_maxsmp()
> -{
> - local smp
> -
> - if smp=$($RUNTIME_arch_run _NO_FILE_4Uhere_ -smp $MAX_SMP |& grep 'SMP CPUs'); then
> - smp=${smp##* }
> - smp=${smp/\(}
> - smp=${smp/\)}
> - echo "Restricting MAX_SMP from ($MAX_SMP) to the max supported ($smp)" >&2
> - MAX_SMP=$smp
> - fi
> -}
> diff --git a/scripts/vmm.bash b/scripts/vmm.bash
> index a1d50ed51981..ef9819f4132c 100644
> --- a/scripts/vmm.bash
> +++ b/scripts/vmm.bash
> @@ -105,6 +105,22 @@ function qemu_parse_premature_failure()
> return 0
> }
>
> +#
> +# Probe for MAX_SMP, in case it's less than the number of host cpus.
> +#
> +function qemu_probe_maxsmp()
> +{
> + local smp
> +
> + if smp=$($RUNTIME_arch_run _NO_FILE_4Uhere_ -smp $MAX_SMP |& grep 'SMP CPUs'); then
> + smp=${smp##* }
> + smp=${smp/\(}
> + smp=${smp/\)}
> + echo "Restricting MAX_SMP from ($MAX_SMP) to the max supported ($smp)" >&2
> + MAX_SMP=$smp
> + fi
> +}
> +
> function kvmtool_parse_premature_failure()
> {
> local log="$@"
> @@ -114,6 +130,12 @@ function kvmtool_parse_premature_failure()
> return 0
> }
>
> +function kvmtool_probe_maxsmp()
> +{
> + echo "kvmtool automatically limits the number of VCPUs to maximum supported"
> + echo "The 'smp' test parameter won't be modified"
> +}
> +
> declare -A vmm_opts=(
> [qemu:nr_cpus]='-smp'
> [qemu:kernel]='-kernel'
> @@ -122,6 +144,7 @@ declare -A vmm_opts=(
> [qemu:default_opts]=''
> [qemu:fixup_return_code]=qemu_fixup_return_code
> [qemu:parse_premature_failure]=qemu_parse_premature_failure
> + [qemu:probe_maxsmp]=qemu_probe_maxsmp
>
> [kvmtool:nr_cpus]='--cpus'
> [kvmtool:kernel]='--kernel'
> @@ -130,6 +153,7 @@ declare -A vmm_opts=(
> [kvmtool:default_opts]="$KVMTOOL_DEFAULT_OPTS"
> [kvmtool:fixup_return_code]=kvmtool_fixup_return_code
> [kvmtool:parse_premature_failure]=kvmtool_parse_premature_failure
> + [kvmtool:probe_maxsmp]=kvmtool_probe_maxsmp
> )
>
> function check_vmm_supported()
> --
> 2.49.0
>

Reviewed-by: Andrew Jones <andrew.jones@linux.dev>