On Wed, Jun 25, 2025 at 04:48:07PM +0100, Alexandru Elisei wrote:
> kvmtool, unless told otherwise, will do its best to make sure that a kernel
> successfully boots in a virtual machine. It does things like automatically
> creating a rootfs and adding extra parameters to the kernel command line.
> This is actively harmful to kvm-unit-tests, because some tests parse the
> kernel command line and they will fail if they encounter the options added
> by kvmtool.
>
> Fortunately for us, kvmtool commit 5613ae26b998 ("Add --nodefaults command
> line argument") addded the --nodefaults kvmtool parameter which disables
> all the implicit virtual machine configuration that cannot be disabled by
> using other parameters, like modifying the kernel command line. So always
> use --nodefaults to allow a test to run.
>
> kvmtool can also be too verbose when running a virtual machine, and this is
> controlled by several parameters. Add those to the default kvmtool command
> line to reduce this verbosity to a minimum.
>
> Before:
>
> $ vm run arm/selftest.flat --cpus 2 --mem 256 --params "setup smp=2 mem=256"
> Info: # lkvm run -k arm/selftest.flat -m 256 -c 2 --name guest-5035
> Unknown subtest
>
> EXIT: STATUS=127
> Warning: KVM compatibility warning.
> virtio-9p device was not detected.
> While you have requested a virtio-9p device, the guest kernel did not
> initialize it.
> Please make sure that the guest kernel was compiled with
> CONFIG_NET_9P_VIRTIO=y enabled in .config.
> Warning: KVM compatibility warning.
> virtio-net device was not detected.
> While you have requested a virtio-net device, the guest kernel did not
> initialize it.
> Please make sure that the guest kernel was compiled with
> CONFIG_VIRTIO_NET=y enabled in .config.
> Info: KVM session ended normally.
>
> After:
>
> $ vm run arm/selftest.flat --nodefaults --network mode=none
> --loglevel=warning --cpus 2 --mem 256 --params "setup smp=2 mem=256"
> PASS: selftest: setup: smp: number of CPUs matches expectation
> INFO: selftest: setup: smp: found 2 CPUs
> PASS: selftest: setup: mem: memory size matches expectation
> INFO: selftest: setup: mem: found 256 MB
> SUMMARY: 2 tests
>
> EXIT: STATUS=1
>
> Note that KVMTOOL_DEFAULT_OPTS can be overwritten by an environment
> variable with the same name, but it's not documented in the help string for
> run_tests.sh. This has been done on purpose, since overwritting
> KVMTOOL_DEFAULT_OPTS should only be necessary for debugging or development
> purposes.
>
> Reviewed-by: Andrew Jones <andrew.jo...@linux.dev>
> Reviewed-by: Shaoqin Huang <shahu...@redhat.com>
> Signed-off-by: Alexandru Elisei <alexandru.eli...@arm.com>
> ---
>
> Changes v3->v4:
>
> * Use vmm_default_opts() instead of indexing into vmm_optname
> * Reworded the help test for --nodefaults as per Shaoqin's suggestion.
>
> scripts/common.bash | 6 +++---
> scripts/vmm.bash | 18 ++++++++++++++++++
> 2 files changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/common.bash b/scripts/common.bash
> index 7c1b89f1b3c2..d5d3101c8089 100644
> --- a/scripts/common.bash
> +++ b/scripts/common.bash
> @@ -37,7 +37,7 @@ function for_each_unittest()
> # -append as a kernel parameter instead of a command
> # line option.
> test_args=""
> - opts=""
> + opts="$(vmm_default_opts)"
> groups=""
> arch=""
> machine=""
> @@ -51,7 +51,7 @@ function for_each_unittest()
> elif [[ $line =~ ^test_args\ *=\ *(.*)$ ]]; then
> test_args="$(vmm_optname_args) ${BASH_REMATCH[1]}"
> elif [[ $line =~ ^$params_name\ *=\ *'"""'(.*)$ ]]; then
> - opts=${BASH_REMATCH[1]}$'\n'
> + opts="$(vmm_defaults_opts) ${BASH_REMATCH[1]}$'\n'"
Could be opts+=" ${BASH_REMATCH[1]}$'\n'", right?
> while read -r -u $fd; do
> #escape backslash newline, but not double
> backslash
> if [[ $opts =~ [^\\]*(\\*)$'\n'$ ]]; then
> @@ -67,7 +67,7 @@ function for_each_unittest()
> fi
> done
> elif [[ $line =~ ^$params_name\ *=\ *(.*)$ ]]; then
> - opts=${BASH_REMATCH[1]}
> + opts="$(vmm_default_opts) ${BASH_REMATCH[1]}"
Same comment.
Not a big deal either way, though, so my r-b stands.
Thanks,
drew
> elif [[ $line =~ ^groups\ *=\ *(.*)$ ]]; then
> groups=${BASH_REMATCH[1]}
> elif [[ $line =~ ^arch\ *=\ *(.*)$ ]]; then
> diff --git a/scripts/vmm.bash b/scripts/vmm.bash
> index 0dd3f971ecdf..368690d62473 100644
> --- a/scripts/vmm.bash
> +++ b/scripts/vmm.bash
> @@ -1,3 +1,14 @@
> +# The following parameters are enabled by default when running a test with
> +# kvmtool:
> +# --nodefaults: suppress VM configuration that cannot be disabled (like
> +# modifying the supplied kernel command line). Otherwise tests
> +# that use the command line will fail without this parameter.
> +# --network mode=none: do not create a network device. kvmtool tries to help
> the
> +# user by automatically create one, and then prints a warning
> +# when the VM terminates if the device hasn't been initialized.
> +# --loglevel=warning: reduce verbosity
> +: "${KVMTOOL_DEFAULT_OPTS:="--nodefaults --network mode=none
> --loglevel=warning"}"
> +
>
> ##############################################################################
> # qemu_fixup_return_code translates the ambiguous exit status in Table1 to
> that
> # in Table2. Table3 simply documents the complete status table.
> @@ -82,11 +93,13 @@ function kvmtool_fixup_return_code()
>
> declare -A vmm_optname=(
> [qemu,args]='-append'
> + [qemu,default_opts]=''
> [qemu,fixup_return_code]=qemu_fixup_return_code
> [qemu,initrd]='-initrd'
> [qemu,nr_cpus]='-smp'
>
> [kvmtool,args]='--params'
> + [kvmtool,default_opts]="$KVMTOOL_DEFAULT_OPTS"
> [kvmtool,fixup_return_code]=kvmtool_fixup_return_code
> [kvmtool,initrd]='--initrd'
> [kvmtool,nr_cpus]='--cpus'
> @@ -97,6 +110,11 @@ function vmm_optname_args()
> echo ${vmm_optname[$(vmm_get_target),args]}
> }
>
> +function vmm_default_opts()
> +{
> + echo ${vmm_optname[$(vmm_get_target),default_opts]}
> +}
> +
> function vmm_fixup_return_code()
> {
> ${vmm_optname[$(vmm_get_target),fixup_return_code]} "$@"
> --
> 2.50.0
>
>
> --
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