[PATCH v2 8/9] tests/qtest/migration: Support more than one QEMU binary

[Fabiano Rosas <farosas@suse.de>]

We have strict rules around migration compatibility between different
QEMU versions but no test to validate the migration state between
different binaries.

Add infrastructure to allow running the migration tests with two
different QEMU binaries as migration source and destination.

The code now recognizes two new environment variables
QTEST_QEMU_BINARY_SRC and QTEST_QEMU_BINARY_DST. In the absence of
either of them, the test will use the QTEST_QEMU_BINARY variable. If
both are missing then the tests are run with single binary as
previously.

The machine type is selected automatically as the latest machine type
version that works with both binaries.

Usage:
QTEST_QEMU_BINARY_SRC=../build-8.2.0/qemu-system-x86_64 \
QTEST_QEMU_BINARY_DST=../build-8.1.0/qemu-system-x86_64 \
./tests/qtest/migration-test

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 tests/qtest/migration-test.c | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

diff --git a/tests/qtest/migration-test.c b/tests/qtest/migration-test.c
index 7c10ac925b..984f52becd 100644
--- a/tests/qtest/migration-test.c
+++ b/tests/qtest/migration-test.c
@@ -66,6 +66,9 @@ static bool got_dst_resume;
  */
 #define DIRTYLIMIT_TOLERANCE_RANGE  25  /* MB/s */
 
+#define QEMU_ENV_SRC "QTEST_QEMU_BINARY_SRC"
+#define QEMU_ENV_DST "QTEST_QEMU_BINARY_DST"
+
 #if defined(__linux__)
 #include <sys/syscall.h>
 #include <sys/vfs.h>
@@ -747,6 +750,7 @@ static int test_migrate_start(QTestState **from, QTestState **to,
     const char *arch = qtest_get_arch();
     const char *memory_size;
     const char *machine;
+    g_autofree char *machine_type = NULL;
 
     if (args->use_shmem) {
         if (!g_file_test("/dev/shm", G_FILE_TEST_IS_DIR)) {
@@ -817,6 +821,10 @@ static int test_migrate_start(QTestState **from, QTestState **to,
         kvm_opts = ",dirty-ring-size=4096";
     }
 
+    machine_type = find_common_machine_version(machine, QEMU_ENV_SRC,
+                                               QEMU_ENV_DST);
+    g_test_message("Using machine type: %s", machine_type);
+
     cmd_source = g_strdup_printf("-accel kvm%s -accel tcg "
                                  "-machine %s "
                                  "-name source,debug-threads=on "
@@ -824,7 +832,7 @@ static int test_migrate_start(QTestState **from, QTestState **to,
                                  "-serial file:%s/src_serial "
                                  "%s %s %s %s %s",
                                  kvm_opts ? kvm_opts : "",
-                                 machine,
+                                 machine_type,
                                  memory_size, tmpfs,
                                  arch_opts ? arch_opts : "",
                                  arch_source ? arch_source : "",
@@ -832,7 +840,7 @@ static int test_migrate_start(QTestState **from, QTestState **to,
                                  args->opts_source ? args->opts_source : "",
                                  ignore_stderr);
     if (!args->only_target) {
-        *from = qtest_init(cmd_source);
+        *from = qtest_init_with_env(QEMU_ENV_SRC, cmd_source);
         qtest_qmp_set_event_callback(*from,
                                      migrate_watch_for_stop,
                                      &got_src_stop);
@@ -846,14 +854,14 @@ static int test_migrate_start(QTestState **from, QTestState **to,
                                  "-incoming %s "
                                  "%s %s %s %s %s",
                                  kvm_opts ? kvm_opts : "",
-                                 machine,
+                                 machine_type,
                                  memory_size, tmpfs, uri,
                                  arch_opts ? arch_opts : "",
                                  arch_target ? arch_target : "",
                                  shmem_opts ? shmem_opts : "",
                                  args->opts_target ? args->opts_target : "",
                                  ignore_stderr);
-    *to = qtest_init(cmd_target);
+    *to = qtest_init_with_env(QEMU_ENV_DST, cmd_target);
     qtest_qmp_set_event_callback(*to,
                                  migrate_watch_for_resume,
                                  &got_dst_resume);
@@ -2792,10 +2800,23 @@ int main(int argc, char **argv)
     bool has_uffd;
     const char *arch;
     g_autoptr(GError) err = NULL;
+    const char *qemu_src = getenv(QEMU_ENV_SRC);
+    const char *qemu_dst = getenv(QEMU_ENV_DST);
     int ret;
 
     g_test_init(&argc, &argv, NULL);
 
+    /*
+     * The default QTEST_QEMU_BINARY must always be provided because
+     * that is what helpers use to query the accel type and
+     * architecture.
+     */
+    if (qemu_src && qemu_dst) {
+        g_test_message("Only one of %s, %s is allowed",
+                       QEMU_ENV_SRC, QEMU_ENV_DST);
+        exit(1);
+    }
+
     has_kvm = qtest_has_accel("kvm");
     has_tcg = qtest_has_accel("tcg");
 
-- 
2.35.3