selftests/vsock: add initial vmtest.sh for vsock

selftests/vsock: add initial vmtest.sh for vsock

This commit introduces a new vmtest.sh runner for vsock.

It uses virtme-ng/qemu to run tests in a VM. The tests validate G2H,
H2G, and loopback. The testing tools from tools/testing/vsock/ are
reused. Currently, only vsock_test is used.

VMCI and hyperv support is included in the config file to be built with
the -b option, though not used in the tests.

Only tested on x86.

To run:

  $ make -C tools/testing/selftests TARGETS=vsock
  $ tools/testing/selftests/vsock/vmtest.sh

or

  $ make -C tools/testing/selftests TARGETS=vsock run_tests

Example runs (after make -C tools/testing/selftests TARGETS=vsock):

$ ./tools/testing/selftests/vsock/vmtest.sh
1..3
ok 0 vm_server_host_client
ok 1 vm_client_host_server
ok 2 vm_loopback
SUMMARY: PASS=3 SKIP=0 FAIL=0
Log: /tmp/vsock_vmtest_m7DI.log

$ ./tools/testing/selftests/vsock/vmtest.sh vm_loopback
1..1
ok 0 vm_loopback
SUMMARY: PASS=1 SKIP=0 FAIL=0
Log: /tmp/vsock_vmtest_a1IO.log

$ mkdir -p ~/scratch
$ make -C tools/testing/selftests install TARGETS=vsock INSTALL_PATH=~/scratch
 [... omitted ...]
$ cd ~/scratch
$ ./run_kselftest.sh
 TAP version 13
 1..1
 # timeout set to 300
 # selftests: vsock: vmtest.sh
 # 1..3
 # ok 0 vm_server_host_client
 # ok 1 vm_client_host_server
 # ok 2 vm_loopback
 # SUMMARY: PASS=3 SKIP=0 FAIL=0
 # Log: /tmp/vsock_vmtest_svEl.log
 ok 1 selftests: vsock: vmtest.sh

Future work can include vsock_diag_test.

Because vsock requires a VM to test anything other than loopback, this
patch adds vmtest.sh as a kselftest itself. This is different than other
systems that have a "vmtest.sh", where it is used as a utility script to
spin up a VM to run the selftests as a guest (but isn't hooked into
kselftest).

Signed-off-by: Bobby Eshleman <bobbyeshleman@gmail.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://patch.msgid.link/20250609-vsock-vmtest-v10-1-7f37198e1cd4@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>