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

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

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>