tests: Add a device_add/del HMP test

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

Signed-off-by Thomas Huth <[email protected]>

---
I've marked the patch as RFC since not all of the required device bug fixes have been merged yet (so this patch can not be included yet without breaking "make check"). It's also sad that "macio-oldworld" currently has to be blacklisted - I tried to find a fix for that device, but I was not able to spot the exact problem so far. So help for fixing that device is very very welcome! The crash can be reproduced like this:

 $ qemu-system-ppc64 -nographic -S -monitor stdio -serial none
 QEMU 2.10.50 monitor - type 'help' for more information
 (qemu) device_add macio-oldworld,id=x
 (qemu) device_del x
 (qemu) **
 ERROR:qom/object.c:1611:object_get_canonical_path_component:
  assertion failed: (obj->parent != NULL)
 Aborted (core dumped)

 tests/test-hmp.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

tests/test-hmp.c +58 -1

index 7a38cdc..e8a25c4 100644
@@ -28,7 +28,6 @@ static const char *hmp_cmds[] = {
     "commit all",
     "cpu-add 1",
     "cpu 0",
-    "device_add ?",
     "device_add usb-mouse,id=mouse1",
     "mouse_button 7",
     "mouse_move 10 10",

@@ -116,6 +115,64 @@ static void test_info_commands(void)
     g_free(info_buf);
 }
 
+/*
+ * People tend to forget to mark internal devices with "user_creatable = false
+ * and these devices can crash QEMU if added via the HMP monitor. So let's run
+ * through all devices and try to add them blindly (without arguments) to see
+ * whether this could crash the QEMU instance.
+ */
+static void test_device_add_commands(void)
+{
+    char *resp, *devices, *devices_buf, *endp;
+
+    devices = devices_buf = hmp("device_add help");
+
+    while (*devices) {
+        /* Ignore header lines etc. */
+        if (strncmp(devices, "name \"", 6)) {
+            devices = strchr(devices, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Extract the device name, ignore parameters and description */
+        devices += 6;
+        endp = strchr(devices, '"');
+        g_assert(endp != NULL);
+        *endp = '\0';
+        /* Check whether it is blacklisted... */
+        if (g_str_equal("macio-oldworld", devices)) {
+            devices = strchr(endp + 1, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Now run the device_add + device_del commands */
+        if (verbose) {
+            fprintf(stderr, "\tdevice_add %s,id=%s\n", devices, devices);
+        }
+        resp = hmp("device_add %s,id=%s", devices, devices);
+        g_free(resp);
+        if (verbose) {
+            fprintf(stderr, "\tdevice_del %s\n", devices);
+        }
+        resp = hmp("device_del %s", devices);
+        g_free(resp);
+        /* And move forward to the next line */
+        devices = strchr(endp + 1, '\n');
+        if (!devices) {
+            break;
+        }
+        devices += 1;
+    }
+
+    g_free(devices_buf);
+}
+
 static void test_machine(gconstpointer data)
 {
     const char *machine = data;

Quoted 105 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

Signed-off-by Thomas Huth <[email protected]>

---
I've marked the patch as RFC since not all of the required device bug fixes have been merged yet (so this patch can not be included yet without breaking "make check"). It's also sad that "macio-oldworld" currently has to be blacklisted - I tried to find a fix for that device, but I was not able to spot the exact problem so far. So help for fixing that device is very very welcome! The crash can be reproduced like this:

 $ qemu-system-ppc64 -nographic -S -monitor stdio -serial none
 QEMU 2.10.50 monitor - type 'help' for more information
 (qemu) device_add macio-oldworld,id=x
 (qemu) device_del x
 (qemu) **
 ERROR:qom/object.c:1611:object_get_canonical_path_component:
  assertion failed: (obj->parent != NULL)
 Aborted (core dumped)

 tests/test-hmp.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

tests/test-hmp.c +58 -1

index 7a38cdc..e8a25c4 100644
@@ -28,7 +28,6 @@ static const char *hmp_cmds[] = {
     "commit all",
     "cpu-add 1",
     "cpu 0",
-    "device_add ?",
     "device_add usb-mouse,id=mouse1",
     "mouse_button 7",
     "mouse_move 10 10",

@@ -116,6 +115,64 @@ static void test_info_commands(void)
     g_free(info_buf);
 }
 
+/*
+ * People tend to forget to mark internal devices with "user_creatable = false
+ * and these devices can crash QEMU if added via the HMP monitor. So let's run
+ * through all devices and try to add them blindly (without arguments) to see
+ * whether this could crash the QEMU instance.
+ */
+static void test_device_add_commands(void)
+{
+    char *resp, *devices, *devices_buf, *endp;
+
+    devices = devices_buf = hmp("device_add help");
+
+    while (*devices) {
+        /* Ignore header lines etc. */
+        if (strncmp(devices, "name \"", 6)) {
+            devices = strchr(devices, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Extract the device name, ignore parameters and description */
+        devices += 6;
+        endp = strchr(devices, '"');
+        g_assert(endp != NULL);
+        *endp = '\0';
+        /* Check whether it is blacklisted... */
+        if (g_str_equal("macio-oldworld", devices)) {
+            devices = strchr(endp + 1, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Now run the device_add + device_del commands */
+        if (verbose) {
+            fprintf(stderr, "\tdevice_add %s,id=%s\n", devices, devices);
+        }
+        resp = hmp("device_add %s,id=%s", devices, devices);
+        g_free(resp);
+        if (verbose) {
+            fprintf(stderr, "\tdevice_del %s\n", devices);
+        }
+        resp = hmp("device_del %s", devices);
+        g_free(resp);
+        /* And move forward to the next line */
+        devices = strchr(endp + 1, '\n');
+        if (!devices) {
+            break;
+        }
+        devices += 1;
+    }
+
+    g_free(devices_buf);
+}
+
 static void test_machine(gconstpointer data)
 {
     const char *machine = data;

tests/test-hmp.c static void test_machine(gconstpointer data) · line 188

Quoted 7 lines

tests/test-hmp.c +1 -0

@@ -125,6 +182,7 @@ static void test_machine(gconstpointer data)
     qtest_start(args);
 
     test_info_commands();
+    test_device_add_commands();
     test_commands();
 
     qtest_end();

This finds devices by parsing output of HMP help. I think you should use introspection instead, like device-introspect-test does. You may want to extract common utility code from there.

The actual device_add and device_del also use HMP. Failures are ignored. A few device_add failures I'd expect:

* There is no suitable bus.

* There are suitable buses, but the default one is full.

* Mandatory parameters are missing, such as device backend.

* The bus doesn't support hot plug (some other bus might).

* The device supports only cold plug with -device, not hot plug with device_add.

I'm afraid the test only tests one of these common failure modes for many devices.

device_del failures I'd expect:

* The device doesn't exist, because it hasn't completed hot plug, yet. In some cases such as ACPI PCI hot plug, hot plug may require guest cooperation, which may take unbounded time. device_add merely kicks off the hot plug then. I can't remember how to poll for completion. I also can't remember why we don't send a QMP event.

The hot plug usually completes quickly, but it may take its own sweet time, or not complete at all, say because the guest doesn't support ACPI, or just doesn't feel like plugging right now.

The test needs to set up a guest that cooperates. I guess that involves libqos; yet another thing I've forgotten.

* Same for device_del. You should wait for the DEVICE_DELETED event with a suitable timeout.

We could improve device_add to cold plug before the machine starts, i.e. between start with -S and the first cont. We could similarly improve device_del to cold plug. Together, that would let you sidestep the hot plug complications.

I guess this test is a case of "if it was easy, we would've done it already"...

Quoted 113 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 111 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

Signed-off-by Thomas Huth <[email protected]>

---
I've marked the patch as RFC since not all of the required device bug fixes have been merged yet (so this patch can not be included yet without breaking "make check"). It's also sad that "macio-oldworld" currently has to be blacklisted - I tried to find a fix for that device, but I was not able to spot the exact problem so far. So help for fixing that device is very very welcome! The crash can be reproduced like this:

 $ qemu-system-ppc64 -nographic -S -monitor stdio -serial none
 QEMU 2.10.50 monitor - type 'help' for more information
 (qemu) device_add macio-oldworld,id=x
 (qemu) device_del x
 (qemu) **
 ERROR:qom/object.c:1611:object_get_canonical_path_component:
  assertion failed: (obj->parent != NULL)
 Aborted (core dumped)

 tests/test-hmp.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

tests/test-hmp.c +59 -1

index 7a38cdc..e8a25c4 100644
@@ -28,7 +28,6 @@ static const char *hmp_cmds[] = {
     "commit all",
     "cpu-add 1",
     "cpu 0",
-    "device_add ?",
     "device_add usb-mouse,id=mouse1",
     "mouse_button 7",
     "mouse_move 10 10",

@@ -116,6 +115,64 @@ static void test_info_commands(void)
     g_free(info_buf);
 }
 
+/*
+ * People tend to forget to mark internal devices with "user_creatable = false
+ * and these devices can crash QEMU if added via the HMP monitor. So let's run
+ * through all devices and try to add them blindly (without arguments) to see
+ * whether this could crash the QEMU instance.
+ */
+static void test_device_add_commands(void)
+{
+    char *resp, *devices, *devices_buf, *endp;
+
+    devices = devices_buf = hmp("device_add help");
+
+    while (*devices) {
+        /* Ignore header lines etc. */
+        if (strncmp(devices, "name \"", 6)) {
+            devices = strchr(devices, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Extract the device name, ignore parameters and description */
+        devices += 6;
+        endp = strchr(devices, '"');
+        g_assert(endp != NULL);
+        *endp = '\0';
+        /* Check whether it is blacklisted... */
+        if (g_str_equal("macio-oldworld", devices)) {
+            devices = strchr(endp + 1, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Now run the device_add + device_del commands */
+        if (verbose) {
+            fprintf(stderr, "\tdevice_add %s,id=%s\n", devices, devices);
+        }
+        resp = hmp("device_add %s,id=%s", devices, devices);
+        g_free(resp);
+        if (verbose) {
+            fprintf(stderr, "\tdevice_del %s\n", devices);
+        }
+        resp = hmp("device_del %s", devices);
+        g_free(resp);
+        /* And move forward to the next line */
+        devices = strchr(endp + 1, '\n');
+        if (!devices) {
+            break;
+        }
+        devices += 1;
+    }
+
+    g_free(devices_buf);
+}
+
 static void test_machine(gconstpointer data)
 {
     const char *machine = data;

@@ -125,6 +182,7 @@ static void test_machine(gconstpointer data)
     qtest_start(args);
 
     test_info_commands();
+    test_device_add_commands();
     test_commands();
 

Quoted 5 lines

tests/test-hmp.c static void test_machine(gconstpointer data) · line 188

Quoted 1 line

tests/test-hmp.c +0 -0

     qtest_end();

This finds devices by parsing output of HMP help. I think you should use introspection instead, like device-introspect-test does. You may want to extract common utility code from there.

Quoted 6 lines

The actual device_add and device_del also use HMP. Failures are ignored. A few device_add failures I'd expect:

* There is no suitable bus.

* There are suitable buses, but the default one is full.

Quoted 1 line

* Mandatory parameters are missing, such as device backend.

Quoted 1 line

* The bus doesn't support hot plug (some other bus might).

Quoted 2 lines

* The device supports only cold plug with -device, not hot plug with device_add.

Quoted 11 lines

I'm afraid the test only tests one of these common failure modes for many devices.

device_del failures I'd expect:

* The device doesn't exist, because it hasn't completed hot plug, yet. In some cases such as ACPI PCI hot plug, hot plug may require guest cooperation, which may take unbounded time. device_add merely kicks off the hot plug then. I can't remember how to poll for completion. I also can't remember why we don't send a QMP event.

Quoted 6 lines

The hot plug usually completes quickly, but it may take its own sweet time, or not complete at all, say because the guest doesn't support ACPI, or just doesn't feel like plugging right now.

The test needs to set up a guest that cooperates. I guess that involves libqos; yet another thing I've forgotten.

Quoted 2 lines

* Same for device_del. You should wait for the DEVICE_DELETED event with a suitable timeout.

Yes, I think that's an interesting problem - although the test
might still be worth it just to see how many issues it finds; I'm
curious how many devices actually work with no parameters though, most seem to fail.

If I'm reading the code right it's creating the device with the same name as the device; I wonder if that always works?

But still, it should mean that if the previous hotplug hasn't really happened then you can move onto the next add.

Quoted 5 lines

We could improve device_add to cold plug before the machine starts, i.e. between start with -S and the first cont. We could similarly improve device_del to cold plug. Together, that would let you sidestep the hot plug complications.

Quoted 2 lines

I guess this test is a case of "if it was easy, we would've done it already"...

Still maybe it's worth it as a start.

Quoted 114 lines · Dr. David Alan Gilbert

Quoted 113 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 111 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

Signed-off-by Thomas Huth <[email protected]>

---
I've marked the patch as RFC since not all of the required device bug fixes have been merged yet (so this patch can not be included yet without breaking "make check"). It's also sad that "macio-oldworld" currently has to be blacklisted - I tried to find a fix for that device, but I was not able to spot the exact problem so far. So help for fixing that device is very very welcome! The crash can be reproduced like this:

 $ qemu-system-ppc64 -nographic -S -monitor stdio -serial none
 QEMU 2.10.50 monitor - type 'help' for more information
 (qemu) device_add macio-oldworld,id=x
 (qemu) device_del x
 (qemu) **
 ERROR:qom/object.c:1611:object_get_canonical_path_component:
  assertion failed: (obj->parent != NULL)
 Aborted (core dumped)

 tests/test-hmp.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

tests/test-hmp.c +59 -1

index 7a38cdc..e8a25c4 100644
@@ -28,7 +28,6 @@ static const char *hmp_cmds[] = {
     "commit all",
     "cpu-add 1",
     "cpu 0",
-    "device_add ?",
     "device_add usb-mouse,id=mouse1",
     "mouse_button 7",
     "mouse_move 10 10",

@@ -116,6 +115,64 @@ static void test_info_commands(void)
     g_free(info_buf);
 }
 
+/*
+ * People tend to forget to mark internal devices with "user_creatable = false
+ * and these devices can crash QEMU if added via the HMP monitor. So let's run
+ * through all devices and try to add them blindly (without arguments) to see
+ * whether this could crash the QEMU instance.
+ */
+static void test_device_add_commands(void)
+{
+    char *resp, *devices, *devices_buf, *endp;
+
+    devices = devices_buf = hmp("device_add help");
+
+    while (*devices) {
+        /* Ignore header lines etc. */
+        if (strncmp(devices, "name \"", 6)) {
+            devices = strchr(devices, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Extract the device name, ignore parameters and description */
+        devices += 6;
+        endp = strchr(devices, '"');
+        g_assert(endp != NULL);
+        *endp = '\0';
+        /* Check whether it is blacklisted... */
+        if (g_str_equal("macio-oldworld", devices)) {
+            devices = strchr(endp + 1, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Now run the device_add + device_del commands */
+        if (verbose) {
+            fprintf(stderr, "\tdevice_add %s,id=%s\n", devices, devices);
+        }
+        resp = hmp("device_add %s,id=%s", devices, devices);
+        g_free(resp);
+        if (verbose) {
+            fprintf(stderr, "\tdevice_del %s\n", devices);
+        }
+        resp = hmp("device_del %s", devices);
+        g_free(resp);
+        /* And move forward to the next line */
+        devices = strchr(endp + 1, '\n');
+        if (!devices) {
+            break;
+        }
+        devices += 1;
+    }
+
+    g_free(devices_buf);
+}
+
 static void test_machine(gconstpointer data)
 {
     const char *machine = data;

@@ -125,6 +182,7 @@ static void test_machine(gconstpointer data)
     qtest_start(args);
 
     test_info_commands();
+    test_device_add_commands();
     test_commands();
 

Quoted 5 lines

Quoted 5 lines

tests/test-hmp.c static void test_machine(gconstpointer data) · line 188

Quoted 1 line

tests/test-hmp.c +0 -0

     qtest_end();

This finds devices by parsing output of HMP help. I think you should use introspection instead, like device-introspect-test does. You may want to extract common utility code from there.

Well, I wrote a HMP test, to simulate what users can do at the HMP prompt. But ok, it's likely to crash QEMU also when using the QMP interface instead ... but then the code should also go into a different .c file, I think.

Quoted 6 lines

Quoted 6 lines

The actual device_add and device_del also use HMP. Failures are ignored. A few device_add failures I'd expect:

* There is no suitable bus.

* There are suitable buses, but the default one is full.

You can partly work around the above two problems by looping a couple of times through the "device_add"s first, before doing the "device_del"s. Then the first iteration adds additional buses which get populated in the second iteration. I can get additional QEMU crashes if I modify my test that way... but currently I lack time for debugging all these crashes, so I don't want to include that in this patch here yet.

Quoted 1 line

Quoted 1 line

* Mandatory parameters are missing, such as device backend.

That's quite hard to handle even with QMP, isn't it? How should a generic test know which parameter have to be populated with which value?

Quoted 1 line

Quoted 1 line

* The bus doesn't support hot plug (some other bus might).

That should not be a problem - at least QEMU should not crash in this situation.

Quoted 2 lines

Quoted 2 lines

* The device supports only cold plug with -device, not hot plug with device_add.

We've got Eduardo's scripts/device-crash-test script for that already, so no need to cover that here.

Quoted 11 lines

Quoted 11 lines

I'm afraid the test only tests one of these common failure modes for many devices.

device_del failures I'd expect:

* The device doesn't exist, because it hasn't completed hot plug, yet. In some cases such as ACPI PCI hot plug, hot plug may require guest cooperation, which may take unbounded time. device_add merely kicks off the hot plug then. I can't remember how to poll for completion. I also can't remember why we don't send a QMP event.

Quoted 6 lines

Quoted 6 lines

The hot plug usually completes quickly, but it may take its own sweet time, or not complete at all, say because the guest doesn't support ACPI, or just doesn't feel like plugging right now.

The test needs to set up a guest that cooperates. I guess that involves libqos; yet another thing I've forgotten.

That was certainly not my scope when I wrote this test. I just want to get rid of these devices that can easily crash QEMU if you just try to add or remove them at the monitor prompt. A more detailed hotplug test should IMHO be done by the individual device tests instead, like it is done in many tests/virtio*.c and tests/usb*.c files already.

Quoted 7 lines

Quoted 2 lines

* Same for device_del. You should wait for the DEVICE_DELETED event with a suitable timeout.

Yes, I think that's an interesting problem - although the test
might still be worth it just to see how many issues it finds; I'm
curious how many devices actually work with no parameters though, most seem to fail.

My test already helped to find lots of problems:

https://git.qemu.org/?p=qemu.git;a=commitdiff;h=f58f25599b72c7479e6a1
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=469f3da42ef4af347fa78
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=574ee06de9c4fe63c90be
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=84ebd3e8c7d4fe955b359
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0d4fa4996fc5ee56ea7d0
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=1f98e55385d11da1dc0de
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=8ccccff9dd7ba24c7a788
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0479097859372a760843a
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=a808c0865b720e22ca292
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04618.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04164.html
https://lists.gnu.org/archive/html/qemu-arm/2017-08/msg00306.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04622.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04635.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg05390.html

... so does it now sound at least a little bit usable?

Quoted 2 lines

If I'm reading the code right it's creating the device with the same name as the device; I wonder if that always works?

Why not? The id is just an arbitrary string, isn't it?

Quoted 9 lines

But still, it should mean that if the previous hotplug hasn't really happened then you can move onto the next add.

Quoted 5 lines

We could improve device_add to cold plug before the machine starts, i.e. between start with -S and the first cont. We could similarly improve device_del to cold plug. Together, that would let you sidestep the hot plug complications.

Quoted 4 lines

Quoted 2 lines

I guess this test is a case of "if it was easy, we would've done it already"...

Still maybe it's worth it as a start.

Agreed that we should finally move to a smarter, QMP-based test. But until someone wrote that, maybe we could include this as a temporary guard to avoid that problems like the ones above creep in again?

Thomas

Quoted 12 lines · * Thomas Huth ([email protected]) wrote:

Quoted 11 lines · Dr. David Alan Gilbert

Quoted 10 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 8 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

Signed-off-by Thomas Huth <[email protected]>

---

Quoted 4 lines

Quoted 2 lines

If I'm reading the code right it's creating the device with the same name as the device; I wonder if that always works?

Why not? The id is just an arbitrary string, isn't it?

I didn't know how arbitrary they were allowed to be and I was also worried they might clash with some existing id.
As an example, I see there's at least one device (SUNW,fdtwo) with a , in it's name - is that legal for an id ?

Quoted 114 lines · Dr. David Alan Gilbert

Quoted 113 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 111 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

Signed-off-by Thomas Huth <[email protected]>

---
I've marked the patch as RFC since not all of the required device bug fixes have been merged yet (so this patch can not be included yet without breaking "make check"). It's also sad that "macio-oldworld" currently has to be blacklisted - I tried to find a fix for that device, but I was not able to spot the exact problem so far. So help for fixing that device is very very welcome! The crash can be reproduced like this:

 $ qemu-system-ppc64 -nographic -S -monitor stdio -serial none
 QEMU 2.10.50 monitor - type 'help' for more information
 (qemu) device_add macio-oldworld,id=x
 (qemu) device_del x
 (qemu) **
 ERROR:qom/object.c:1611:object_get_canonical_path_component:
  assertion failed: (obj->parent != NULL)
 Aborted (core dumped)

 tests/test-hmp.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

tests/test-hmp.c +59 -1

index 7a38cdc..e8a25c4 100644
@@ -28,7 +28,6 @@ static const char *hmp_cmds[] = {
     "commit all",
     "cpu-add 1",
     "cpu 0",
-    "device_add ?",
     "device_add usb-mouse,id=mouse1",
     "mouse_button 7",
     "mouse_move 10 10",

@@ -116,6 +115,64 @@ static void test_info_commands(void)
     g_free(info_buf);
 }
 
+/*
+ * People tend to forget to mark internal devices with "user_creatable = false
+ * and these devices can crash QEMU if added via the HMP monitor. So let's run
+ * through all devices and try to add them blindly (without arguments) to see
+ * whether this could crash the QEMU instance.
+ */
+static void test_device_add_commands(void)
+{
+    char *resp, *devices, *devices_buf, *endp;
+
+    devices = devices_buf = hmp("device_add help");
+
+    while (*devices) {
+        /* Ignore header lines etc. */
+        if (strncmp(devices, "name \"", 6)) {
+            devices = strchr(devices, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Extract the device name, ignore parameters and description */
+        devices += 6;
+        endp = strchr(devices, '"');
+        g_assert(endp != NULL);
+        *endp = '\0';
+        /* Check whether it is blacklisted... */
+        if (g_str_equal("macio-oldworld", devices)) {
+            devices = strchr(endp + 1, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Now run the device_add + device_del commands */
+        if (verbose) {
+            fprintf(stderr, "\tdevice_add %s,id=%s\n", devices, devices);
+        }
+        resp = hmp("device_add %s,id=%s", devices, devices);
+        g_free(resp);
+        if (verbose) {
+            fprintf(stderr, "\tdevice_del %s\n", devices);
+        }
+        resp = hmp("device_del %s", devices);
+        g_free(resp);
+        /* And move forward to the next line */
+        devices = strchr(endp + 1, '\n');
+        if (!devices) {
+            break;
+        }
+        devices += 1;
+    }
+
+    g_free(devices_buf);
+}
+
 static void test_machine(gconstpointer data)
 {
     const char *machine = data;

@@ -125,6 +182,7 @@ static void test_machine(gconstpointer data)
     qtest_start(args);
 
     test_info_commands();
+    test_device_add_commands();
     test_commands();
 

Quoted 5 lines

Quoted 5 lines

tests/test-hmp.c static void test_machine(gconstpointer data) · line 188

Quoted 1 line

tests/test-hmp.c +0 -0

     qtest_end();

This finds devices by parsing output of HMP help. I think you should use introspection instead, like device-introspect-test does. You may want to extract common utility code from there.

Well, I wrote a HMP test, to simulate what users can do at the HMP prompt. But ok, it's likely to crash QEMU also when using the QMP interface instead ... but then the code should also go into a different .c file, I think.

Quoted 5 lines

Quoted 5 lines

The actual device_add and device_del also use HMP. Failures are ignored. A few device_add failures I'd expect:

* There is no suitable bus.

Quoted 1 line

Quoted 1 line

* There are suitable buses, but the default one is full.

You can partly work around the above two problems by looping a couple of times through the "device_add"s first, before doing the "device_del"s. Then the first iteration adds additional buses which get populated in the second iteration. I can get additional QEMU crashes if I modify my test that way... but currently I lack time for debugging all these crashes, so I don't want to include that in this patch here yet.

Quoted 1 line

Quoted 1 line

* Mandatory parameters are missing, such as device backend.

That's quite hard to handle even with QMP, isn't it? How should a generic test know which parameter have to be populated with which value?

Quoted 1 line

Quoted 1 line

* The bus doesn't support hot plug (some other bus might).

That should not be a problem - at least QEMU should not crash in this situation.

Quoted 2 lines

Quoted 2 lines

* The device supports only cold plug with -device, not hot plug with device_add.

We've got Eduardo's scripts/device-crash-test script for that already, so no need to cover that here.

Quoted 15 lines

Quoted 15 lines

I'm afraid the test only tests one of these common failure modes for many devices.

device_del failures I'd expect:

* The device doesn't exist, because it hasn't completed hot plug, yet. In some cases such as ACPI PCI hot plug, hot plug may require guest cooperation, which may take unbounded time. device_add merely kicks off the hot plug then. I can't remember how to poll for completion. I also can't remember why we don't send a QMP event.

The hot plug usually completes quickly, but it may take its own sweet time, or not complete at all, say because the guest doesn't support ACPI, or just doesn't feel like plugging right now.

Quoted 2 lines

Quoted 2 lines

The test needs to set up a guest that cooperates. I guess that involves libqos; yet another thing I've forgotten.

That was certainly not my scope when I wrote this test. I just want to get rid of these devices that can easily crash QEMU if you just try to add or remove them at the monitor prompt. A more detailed hotplug test should IMHO be done by the individual device tests instead, like it is done in many tests/virtio*.c and tests/usb*.c files already.

Quoted 7 lines

Quoted 2 lines

* Same for device_del. You should wait for the DEVICE_DELETED event with a suitable timeout.

Yes, I think that's an interesting problem - although the test
might still be worth it just to see how many issues it finds; I'm
curious how many devices actually work with no parameters though, most seem to fail.

My test already helped to find lots of problems:

https://git.qemu.org/?p=qemu.git;a=commitdiff;h=f58f25599b72c7479e6a1
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=469f3da42ef4af347fa78
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=574ee06de9c4fe63c90be
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=84ebd3e8c7d4fe955b359
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0d4fa4996fc5ee56ea7d0
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=1f98e55385d11da1dc0de
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=8ccccff9dd7ba24c7a788
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0479097859372a760843a
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=a808c0865b720e22ca292
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04618.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04164.html
https://lists.gnu.org/archive/html/qemu-arm/2017-08/msg00306.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04622.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04635.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg05390.html

... so does it now sound at least a little bit usable?

Quoted 2 lines

If I'm reading the code right it's creating the device with the same name as the device; I wonder if that always works?

Why not? The id is just an arbitrary string, isn't it?

Quoted 8 lines

But still, it should mean that if the previous hotplug hasn't really happened then you can move onto the next add.

Quoted 5 lines

We could improve device_add to cold plug before the machine starts, i.e. between start with -S and the first cont. We could similarly improve device_del to cold plug. Together, that would let you sidestep the hot plug complications.

Quoted 4 lines

Quoted 2 lines

I guess this test is a case of "if it was easy, we would've done it already"...

Still maybe it's worth it as a start.

Agreed that we should finally move to a smarter, QMP-based test. But until someone wrote that, maybe we could include this as a temporary guard to avoid that problems like the ones above creep in again?

Quoted 121 lines · Thomas Huth

Quoted 114 lines · Dr. David Alan Gilbert

Quoted 113 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 111 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

Signed-off-by Thomas Huth <[email protected]>

---
I've marked the patch as RFC since not all of the required device bug fixes have been merged yet (so this patch can not be included yet without breaking "make check"). It's also sad that "macio-oldworld" currently has to be blacklisted - I tried to find a fix for that device, but I was not able to spot the exact problem so far. So help for fixing that device is very very welcome! The crash can be reproduced like this:

 $ qemu-system-ppc64 -nographic -S -monitor stdio -serial none
 QEMU 2.10.50 monitor - type 'help' for more information
 (qemu) device_add macio-oldworld,id=x
 (qemu) device_del x
 (qemu) **
 ERROR:qom/object.c:1611:object_get_canonical_path_component:
  assertion failed: (obj->parent != NULL)
 Aborted (core dumped)

 tests/test-hmp.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

tests/test-hmp.c +59 -1

index 7a38cdc..e8a25c4 100644
@@ -28,7 +28,6 @@ static const char *hmp_cmds[] = {
     "commit all",
     "cpu-add 1",
     "cpu 0",
-    "device_add ?",
     "device_add usb-mouse,id=mouse1",
     "mouse_button 7",
     "mouse_move 10 10",

@@ -116,6 +115,64 @@ static void test_info_commands(void)
     g_free(info_buf);
 }
 
+/*
+ * People tend to forget to mark internal devices with "user_creatable = false
+ * and these devices can crash QEMU if added via the HMP monitor. So let's run
+ * through all devices and try to add them blindly (without arguments) to see
+ * whether this could crash the QEMU instance.
+ */
+static void test_device_add_commands(void)
+{
+    char *resp, *devices, *devices_buf, *endp;
+
+    devices = devices_buf = hmp("device_add help");
+
+    while (*devices) {
+        /* Ignore header lines etc. */
+        if (strncmp(devices, "name \"", 6)) {
+            devices = strchr(devices, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Extract the device name, ignore parameters and description */
+        devices += 6;
+        endp = strchr(devices, '"');
+        g_assert(endp != NULL);
+        *endp = '\0';
+        /* Check whether it is blacklisted... */
+        if (g_str_equal("macio-oldworld", devices)) {
+            devices = strchr(endp + 1, '\n');
+            if (!devices) {
+                break;
+            }
+            devices += 1;
+            continue;
+        }
+        /* Now run the device_add + device_del commands */
+        if (verbose) {
+            fprintf(stderr, "\tdevice_add %s,id=%s\n", devices, devices);
+        }
+        resp = hmp("device_add %s,id=%s", devices, devices);
+        g_free(resp);
+        if (verbose) {
+            fprintf(stderr, "\tdevice_del %s\n", devices);
+        }
+        resp = hmp("device_del %s", devices);
+        g_free(resp);
+        /* And move forward to the next line */
+        devices = strchr(endp + 1, '\n');
+        if (!devices) {
+            break;
+        }
+        devices += 1;
+    }
+
+    g_free(devices_buf);
+}
+
 static void test_machine(gconstpointer data)
 {
     const char *machine = data;

@@ -125,6 +182,7 @@ static void test_machine(gconstpointer data)
     qtest_start(args);
 
     test_info_commands();
+    test_device_add_commands();
     test_commands();
 

Quoted 5 lines

Quoted 5 lines

tests/test-hmp.c static void test_machine(gconstpointer data) · line 188

Quoted 1 line

tests/test-hmp.c +0 -0

     qtest_end();

This finds devices by parsing output of HMP help. I think you should use introspection instead, like device-introspect-test does. You may want to extract common utility code from there.

Quoted 4 lines

Well, I wrote a HMP test, to simulate what users can do at the HMP prompt. But ok, it's likely to crash QEMU also when using the QMP interface instead ... but then the code should also go into a different .c file, I think.

HMP device_add is a trivial wrapper around QMP, as is proper:

    void hmp_device_add(Monitor *mon, const QDict *qdict)
    {
        Error *err = NULL;

        qmp_device_add((QDict *)qdict, NULL, &err);
        hmp_handle_error(mon, &err);
    }

If anything ever breaks in this wrapper, it won't be specific to HMP device_add.

Quoted 5 lines

Quoted 5 lines

Quoted 5 lines

The actual device_add and device_del also use HMP. Failures are ignored. A few device_add failures I'd expect:

* There is no suitable bus.

Quoted 8 lines

Quoted 1 line

Quoted 1 line

* There are suitable buses, but the default one is full.

You can partly work around the above two problems by looping a couple of times through the "device_add"s first, before doing the "device_del"s. Then the first iteration adds additional buses which get populated in the second iteration. I can get additional QEMU crashes if I modify my test that way... but currently I lack time for debugging all these crashes, so I don't want to include that in this patch here yet.

Kind of a random walk.

Eduardo has been working on "socket introspection", i.e. means to find available "sockets" for devices to plug into. Could be used to for a more directed walk. Eduardo, any thoughts?

Quoted 5 lines

Quoted 2 lines

Quoted 2 lines

* Mandatory parameters are missing, such as device backend.

That's quite hard to handle even with QMP, isn't it? How should a generic test know which parameter have to be populated with which value?

It could perhaps populate sufficiently generic parameters such as common backends.

Sadly, device-list-properties is weak, and unless we improve or replace it, this would involve somewhat ugly hardcoding of descriptions. For instance, we'd have to recognize from

    {"name": "netdev", "description": "ID of a netdev to use as a backend", "type": "str"}

that property netdev is a network backend, and very likely mandatory.

Quoted 4 lines

Quoted 1 line

Quoted 1 line

* The bus doesn't support hot plug (some other bus might).

That should not be a problem - at least QEMU should not crash in this situation.

Yes, and testing that has some value. It doesn't test the device, though, only the qdev core.

I don't mean to suggest your test is useless. I'm merely pointing at some gaping coverage holes :)

Quoted 3 lines

Quoted 2 lines

Quoted 2 lines

* The device supports only cold plug with -device, not hot plug with device_add.

Quoted 2 lines

We've got Eduardo's scripts/device-crash-test script for that already, so no need to cover that here.

Point taken. So this test is really about hot plug / unplug. Suggest to clarify the commit message: s/add them blindly/hotplug and unplug them blindly/.

Quoted 16 lines

Quoted 16 lines

Quoted 16 lines

I'm afraid the test only tests one of these common failure modes for many devices.

device_del failures I'd expect:

* The device doesn't exist, because it hasn't completed hot plug, yet. In some cases such as ACPI PCI hot plug, hot plug may require guest cooperation, which may take unbounded time. device_add merely kicks off the hot plug then. I can't remember how to poll for completion. I also can't remember why we don't send a QMP event.

The hot plug usually completes quickly, but it may take its own sweet time, or not complete at all, say because the guest doesn't support ACPI, or just doesn't feel like plugging right now.

Quoted 8 lines

Quoted 2 lines

Quoted 2 lines

The test needs to set up a guest that cooperates. I guess that involves libqos; yet another thing I've forgotten.

That was certainly not my scope when I wrote this test. I just want to get rid of these devices that can easily crash QEMU if you just try to add or remove them at the monitor prompt. A more detailed hotplug test should IMHO be done by the individual device tests instead, like it is done in many tests/virtio*.c and tests/usb*.c files already.

I'm not trying to talk you into widening the scope of your test. I am pointing out that your testing of unplug is racy, and may therefore miss failures randomly: if hotplug is slow, device_del won't actually do anything interesting.

Quoted 26 lines

Quoted 7 lines

Quoted 2 lines

* Same for device_del. You should wait for the DEVICE_DELETED event with a suitable timeout.

Yes, I think that's an interesting problem - although the test
might still be worth it just to see how many issues it finds; I'm
curious how many devices actually work with no parameters though, most seem to fail.

My test already helped to find lots of problems:

https://git.qemu.org/?p=qemu.git;a=commitdiff;h=f58f25599b72c7479e6a1
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=469f3da42ef4af347fa78
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=574ee06de9c4fe63c90be
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=84ebd3e8c7d4fe955b359
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0d4fa4996fc5ee56ea7d0
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=1f98e55385d11da1dc0de
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=8ccccff9dd7ba24c7a788
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=0479097859372a760843a
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=a808c0865b720e22ca292
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04618.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04164.html
https://lists.gnu.org/archive/html/qemu-arm/2017-08/msg00306.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04622.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg04635.html
https://lists.gnu.org/archive/html/qemu-devel/2017-08/msg05390.html

Quoted 1 line

... so does it now sound at least a little bit usable?

I don't doubt it is, but its limitations need to be understood and either relaxed or documented.

Quoted 4 lines

Quoted 2 lines

If I'm reading the code right it's creating the device with the same name as the device; I wonder if that always works?

Why not? The id is just an arbitrary string, isn't it?

Since you're using HMP, you get to quote ',', which occurs in some device names[*]. Enjoy! ;-P

Picking IDs that aren't anti-social may be easier.

Quoted 8 lines

Quoted 8 lines

But still, it should mean that if the previous hotplug hasn't really happened then you can move onto the next add.

Quoted 5 lines

We could improve device_add to cold plug before the machine starts, i.e. between start with -S and the first cont. We could similarly improve device_del to cold plug. Together, that would let you sidestep the hot plug complications.

Quoted 8 lines

Quoted 4 lines

Quoted 2 lines

I guess this test is a case of "if it was easy, we would've done it already"...

Still maybe it's worth it as a start.

Agreed that we should finally move to a smarter, QMP-based test. But until someone wrote that, maybe we could include this as a temporary guard to avoid that problems like the ones above creep in again?

I think its limitations need to be understood to a useful degree, and either relaxed or documented.

[*] Blame IEEE 1275 device trees.

Quoted 11 lines · Markus Armbruster

Quoted 9 lines · Thomas Huth

Quoted 8 lines · Dr. David Alan Gilbert

Quoted 7 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 5 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

Quoted 9 lines

Quoted 5 lines

Quoted 2 lines

Quoted 2 lines

* The device supports only cold plug with -device, not hot plug with device_add.

We've got Eduardo's scripts/device-crash-test script for that already, so no need to cover that here.

Point taken. So this test is really about hot plug / unplug. Suggest to clarify the commit message: s/add them blindly/hotplug and unplug them blindly/.

We could extend device-crash-test to test device_add too, as it already has extra code to deal with known crashes and testing multiple machine-types. Also, any additional code we write to ensure we add mandatory arguments or plug only to valid buses would apply to both -device and device_add. I also think Python test code is easier to maintain and extend, but that's just my personal preference.

Quoted 9 lines

Quoted 4 lines

Quoted 2 lines

If I'm reading the code right it's creating the device with the same name as the device; I wonder if that always works?

Why not? The id is just an arbitrary string, isn't it?

Since you're using HMP, you get to quote ',', which occurs in some device names[*]. Enjoy! ;-P

Picking IDs that aren't anti-social may be easier.

Quoted 12 lines · Eduardo Habkost

Quoted 11 lines · Markus Armbruster

Quoted 9 lines · Thomas Huth

Quoted 8 lines · Dr. David Alan Gilbert

Quoted 7 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 5 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

[...]

Quoted 10 lines

Quoted 9 lines

Quoted 5 lines

Quoted 2 lines

Quoted 2 lines

* The device supports only cold plug with -device, not hot plug with device_add.

We've got Eduardo's scripts/device-crash-test script for that already, so no need to cover that here.

Point taken. So this test is really about hot plug / unplug. Suggest to clarify the commit message: s/add them blindly/hotplug and unplug them blindly/.

Quoted 7 lines

We could extend device-crash-test to test device_add too, as it already has extra code to deal with known crashes and testing multiple machine-types. Also, any additional code we write to ensure we add mandatory arguments or plug only to valid buses would apply to both -device and device_add. I also think Python test code is easier to maintain and extend, but that's just my personal preference.

Adding device_add/del support to device-crash-test is certainly an option. The problem is that nobody runs it by default, so this won't help to avoid that new problems are being committed to the repository.

I think we really should have a test for "make check", too. So would my test be acceptable if I'd rewrite it to use QMP instead (I don't think I could do the full list that Markus mentioned, but at least a basic test via QMP as a start)?

Quoted 36 lines · Thomas Huth

Quoted 12 lines · Eduardo Habkost

Quoted 11 lines · Markus Armbruster

Quoted 9 lines · Thomas Huth

Quoted 8 lines · Dr. David Alan Gilbert

Quoted 7 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 5 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

[...]

Quoted 10 lines

Quoted 9 lines

Quoted 5 lines

Quoted 2 lines

Quoted 2 lines

* The device supports only cold plug with -device, not hot plug with device_add.

We've got Eduardo's scripts/device-crash-test script for that already, so no need to cover that here.

Point taken. So this test is really about hot plug / unplug. Suggest to clarify the commit message: s/add them blindly/hotplug and unplug them blindly/.

Quoted 7 lines

We could extend device-crash-test to test device_add too, as it already has extra code to deal with known crashes and testing multiple machine-types. Also, any additional code we write to ensure we add mandatory arguments or plug only to valid buses would apply to both -device and device_add. I also think Python test code is easier to maintain and extend, but that's just my personal preference.

Adding device_add/del support to device-crash-test is certainly an option. The problem is that nobody runs it by default, so this won't help to avoid that new problems are being committed to the repository.

Quoted 4 lines

I think we really should have a test for "make check", too. So would my test be acceptable if I'd rewrite it to use QMP instead (I don't think I could do the full list that Markus mentioned, but at least a basic test via QMP as a start)?

We can run device-crash-test on "make check", we just need to choose what's the subset of tests we want to run (because testing all machine+device+target combinations would take too long).

Quoted 42 lines · Eduardo Habkost

Quoted 40 lines · Thomas Huth

Quoted 12 lines · Eduardo Habkost

Quoted 11 lines · Markus Armbruster

Quoted 9 lines · Thomas Huth

Quoted 8 lines · Dr. David Alan Gilbert

Quoted 7 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 5 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

[...]

Quoted 10 lines

Quoted 9 lines

Quoted 5 lines

Quoted 2 lines

Quoted 2 lines

* The device supports only cold plug with -device, not hot plug with device_add.

We've got Eduardo's scripts/device-crash-test script for that already, so no need to cover that here.

Point taken. So this test is really about hot plug / unplug. Suggest to clarify the commit message: s/add them blindly/hotplug and unplug them blindly/.

Quoted 7 lines

We could extend device-crash-test to test device_add too, as it already has extra code to deal with known crashes and testing multiple machine-types. Also, any additional code we write to ensure we add mandatory arguments or plug only to valid buses would apply to both -device and device_add. I also think Python test code is easier to maintain and extend, but that's just my personal preference.

Adding device_add/del support to device-crash-test is certainly an option. The problem is that nobody runs it by default, so this won't help to avoid that new problems are being committed to the repository.

I think we really should have a test for "make check", too. So would my test be acceptable if I'd rewrite it to use QMP instead (I don't think I could do the full list that Markus mentioned, but at least a basic test via QMP as a start)?

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We can run device-crash-test on "make check", we just need to choose what's the subset of tests we want to run (because testing all machine+device+target combinations would take too long).

Maybe we should just run it one time for every machine - and try to add all available devices at once?

Quoted 47 lines · Thomas Huth

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Quoted 12 lines · Eduardo Habkost

Quoted 11 lines · Markus Armbruster

Quoted 9 lines · Thomas Huth

Quoted 8 lines · Dr. David Alan Gilbert

Quoted 7 lines · * Markus Armbruster ([email protected]) wrote:

Quoted 5 lines · Thomas Huth

People tend to forget to mark internal devices with "user_creatable = false or hotpluggable = false, and these devices can crash QEMU if added via the HMP monitor. So let's add a test to run through all devices and that tries to add them blindly (without arguments) to see whether this could crash the QEMU instance.

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* The device supports only cold plug with -device, not hot plug with device_add.

We've got Eduardo's scripts/device-crash-test script for that already, so no need to cover that here.

Point taken. So this test is really about hot plug / unplug. Suggest to clarify the commit message: s/add them blindly/hotplug and unplug them blindly/.

Quoted 7 lines

We could extend device-crash-test to test device_add too, as it already has extra code to deal with known crashes and testing multiple machine-types. Also, any additional code we write to ensure we add mandatory arguments or plug only to valid buses would apply to both -device and device_add. I also think Python test code is easier to maintain and extend, but that's just my personal preference.

Quoted 8 lines

Adding device_add/del support to device-crash-test is certainly an option. The problem is that nobody runs it by default, so this won't help to avoid that new problems are being committed to the repository.

I think we really should have a test for "make check", too. So would my test be acceptable if I'd rewrite it to use QMP instead (I don't think I could do the full list that Markus mentioned, but at least a basic test via QMP as a start)?

We can run device-crash-test on "make check", we just need to choose what's the subset of tests we want to run (because testing all machine+device+target combinations would take too long).

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Maybe we should just run it one time for every machine - and try to add all available devices at once?

Yes, it makes sense. I will keep that in mind when trying to implement device_add support on device-crash-test (but if anybody wants to volunteer to implement it, be my guest).