[kvm-unit-tests PATCH v4 07/13] scripts: Add default arguments for kvmtool

[Alexandru Elisei]

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.jones at linux.dev>
Reviewed-by: Shaoqin Huang <shahuang at redhat.com>
Signed-off-by: Alexandru Elisei <alexandru.elisei at 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'"
 			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]}"
 		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