[Qemu-devel] [RFC PATCH 1/2] libqtest: add qtest_accel() to avoid warnings when kvm is not available

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

only warn once about it.

- kernel without kvm:

    # make check-qtest-x86_64
      GTESTER check-qtest-x86_64
    Could not access KVM kernel module: No such device
    qemu-system-x86_64: failed to initialize KVM: No such device
    qemu-system-x86_64: Back to tcg accelerator

- tests ran as user:

    $ make check-qtest-x86_64
      GTESTER check-qtest-x86_64
    Could not access KVM kernel module: Permission denied
    qemu-system-x86_64: failed to initialize KVM: Permission denied
    qemu-system-x86_64: Back to tcg accelerator

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
 tests/libqtest.h |  8 ++++++++
 tests/libqtest.c | 18 ++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/tests/libqtest.h b/tests/libqtest.h
index 38bc1e9953..24e03148eb 100644
--- a/tests/libqtest.h
+++ b/tests/libqtest.h
@@ -927,4 +927,12 @@ QDict *qmp_fd(int fd, const char *fmt, ...);
  */
 void qtest_cb_for_every_machine(void (*cb)(const char *machine));
 
+/**
+ * qtest_accel:
+ * @accel: List of accelerators
+ *
+ *  Filter accelerators accessible on the host.
+ */
+const char *qtest_accel(const char *accel);
+
 #endif
diff --git a/tests/libqtest.c b/tests/libqtest.c
index b9a1f180e1..d2dfca35a3 100644
--- a/tests/libqtest.c
+++ b/tests/libqtest.c
@@ -987,3 +987,21 @@ void qtest_cb_for_every_machine(void (*cb)(const char *machine))
     qtest_end();
     QDECREF(response);
 }
+
+const char *qtest_accel(const char *accel)
+{
+    static bool kvm_accessible = true;
+
+    if (strlen(accel) <= 4 || strncmp(accel, "kvm:", 4)) {
+        return accel; /* no match */
+    }
+
+    if (!kvm_accessible || !access("/dev/kvm", W_OK)) {
+        accel += 4; /* skip "kvm:" */
+        if (kvm_accessible) {
+            kvm_accessible = false; /* warn once */
+            g_printerr("kvm not accessible, using %s\n", accel);
+        }
+    }
+    return accel;
+}
-- 
2.14.1