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Re: [libvirt] [PATCH V1 1/6] Add QMP probing for TPM



On 03/14/2013 10:20 AM, Daniel P. Berrange wrote:
On Wed, Mar 13, 2013 at 12:03:49PM -0400, Stefan Berger wrote:
Probe for QEMU's QMP TPM support by querying the lists of
supported TPM models (query-tpm-models) and backend types
(query-tpm-types).

The setting of the capability flags following the strings
returned from the commands above is only provided in the
patch where domain_conf.c gets TPM support due to dependencies
on functions only introduced there.

Signed-off-by: Stefan Berger <stefanb linux vnet ibm com>

---
  src/libvirt_private.syms     |    1
  src/qemu/qemu_capabilities.c |   61 ++++++++++++++++++++++++++++
  src/qemu/qemu_capabilities.h |    3 +
  src/qemu/qemu_monitor.c      |   44 ++++++++++++++++++++
  src/qemu/qemu_monitor.h      |    6 ++
  src/qemu/qemu_monitor_json.c |   91 +++++++++++++++++++++++++++++++++++++++++++
  src/qemu/qemu_monitor_json.h |    8 +++
  src/util/virutil.c           |   14 ++++++
  src/util/virutil.h           |    3 +
  9 files changed, 231 insertions(+)

Index: libvirt/src/qemu/qemu_capabilities.c
===================================================================
--- libvirt.orig/src/qemu/qemu_capabilities.c
+++ libvirt/src/qemu/qemu_capabilities.c
@@ -210,6 +210,8 @@ VIR_ENUM_IMPL(virQEMUCaps, QEMU_CAPS_LAS
"rng-random", /* 130 */
                "rng-egd",
+              "tpm-passthrough",
+              "tpm-tis",
      );
struct _virQEMUCaps {
Index: libvirt/src/qemu/qemu_capabilities.h
===================================================================
--- libvirt.orig/src/qemu/qemu_capabilities.h
+++ libvirt/src/qemu/qemu_capabilities.h
@@ -171,6 +171,8 @@ enum virQEMUCapsFlags {
      QEMU_CAPS_OBJECT_RNG_RANDOM  = 130, /* the rng-random backend for
                                             virtio rng */
      QEMU_CAPS_OBJECT_RNG_EGD     = 131, /* EGD protocol daemon for rng */
+    QEMU_CAPS_DEVICE_TPM_PASSTHROUGH = 132, /* -tpmdev passthrough */
+    QEMU_CAPS_DEVICE_TPM_TIS     = 133, /* -device tpm_tis */
I'm wondering whether we really need to spend 2 capability bits on
this. Is it possible to build QEMU such that we have one, but not
the other ? If not then one capability would suffice

I had it with a single capability bit QEMU_CAPS_DEVICE_TPM *and* was reading the strings about the supported models and backend types from QEMU via QMP and held them in qemuCaps. When building the command line I then compared the intended model and backend type to be used against the list held in qemuCaps. That went fine until I wrote the test. There we end up using a pseudo executable (/usr/bin/qemu or so) as well and the test failed because it wasn't probed for the models and types. So I ended up changing the code so that I can set those bits inside the tests rather than having to set the needed strings in the array.

Presumably query-tpm-models and query-tpm-lists allows us to report an error from libvirt about non-availability of a model/backend type rather than having QEMU report an error which we reflect to the user.


+
+static int
+qemuMonitorJSONGetStringArray(qemuMonitorPtr mon, const char *qmpCmd,
+                              char ***array)
+{
+    int ret;
+    virJSONValuePtr cmd;
+    virJSONValuePtr reply = NULL;
+    virJSONValuePtr data;
+    char **list = NULL;
+    int n = 0;
+    size_t i;
+
+    *array = NULL;
+
+    if (!(cmd = qemuMonitorJSONMakeCommand(qmpCmd, NULL)))
+        return -1;
+
+    ret = qemuMonitorJSONCommand(mon, cmd, &reply);
+
+    if (ret == 0)
+        ret = qemuMonitorJSONCheckError(cmd, reply);
+
+    if (ret < 0)
+        goto cleanup;
+
+    ret = -1;
+
+    if (!(data = virJSONValueObjectGet(reply, "return"))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("%s reply was missing return data"),
+                       qmpCmd);
+        goto cleanup;
+    }

I think everything above this point should be in the main monitor APIs,
and this method concern itself solely with converting the virJSONValuePtr
into a string array, not actually executing command. This makes the code
more portable for use in commands which need control over the command
execution to handle errors / pass arguments.

Hm, this surprises me since this would put JSON specific code into the monitor APIs (qemu_monitor.c) while qemu_monitor.c typically only serves as a dispatcher for either text monitor or json monitor.


Index: libvirt/src/libvirt_private.syms===================================================================
--- libvirt.orig/src/libvirt_private.syms
+++ libvirt/src/libvirt_private.syms
@@ -1886,6 +1886,7 @@ virSetUIDGIDWithCaps;
  virSkipSpaces;
  virSkipSpacesAndBackslash;
  virSkipSpacesBackwards;
+virStrArrayHasString;
  virStrcpy;
  virStrIsPrint;
  virStrncpy;
Index: libvirt/src/util/virutil.c
===================================================================
--- libvirt.orig/src/util/virutil.c
+++ libvirt/src/util/virutil.c
@@ -3379,3 +3379,17 @@ cleanup:
      VIR_FREE(buf);
      return ret;
  }
+
+
+bool
+virStrArrayHasString(char **strings, size_t n_strings, const char *needle)
+{
+    size_t i;
+
+    for (i = 0; i < n_strings; i++) {
+        if (STREQ(strings[i], needle))
+            return true;
+    }
+
+    return false;
+}
Index: libvirt/src/util/virutil.h
===================================================================
--- libvirt.orig/src/util/virutil.h
+++ libvirt/src/util/virutil.h
@@ -297,4 +297,7 @@ int virGetDeviceUnprivSGIO(const char *p
  char * virGetUnprivSGIOSysfsPath(const char *path,
                                   const char *sysfs_dir);
+bool virStrArrayHasString(char **strings, size_t n_strings,
+                          const char *needle);
+
  #endif /* __VIR_UTIL_H__ */
The virStrArrayHasString method doesn't appear to be used in this patch.
If some other patch needs this still, then it should be a separate patch
from the monitor code.
Ok, I'll split this off into a patch of its own.

   Stefan


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