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[libvirt] [PATCH v4] qemu: call drive_del in DetachPciDiskDevice



Currently libvirt doesn't confirm whether the guest has responded to the
disk removal request.  In some cases this can leave the guest with
continued access to the device while the mgmt layer believes that it has
been removed.  With a recent qemu monitor command[1] we can
deterministically revoke a guests access to the disk (on the QEMU side)
to ensure no futher access is permitted.

This patch adds support for the drive_del() command and introduces it
in the disk removal paths.  If the guest is running in a QEMU without this
command we currently explicitly check for unknown command/CommandNotFound
and log the issue.

If QEMU supports the command we issue the drive_del command after we attempt
to remove the device.  The guest may respond and remove the block device
before we get to attempt to call drive_del.  In that case, we explicitly check
for 'Device not found' from the monitor indicating that the target drive
was auto-deleted upon guest responds to the device removal notification.

1. http://thread.gmane.org/gmane.comp.emulators.qemu/84255

Signed-off-by: Ryan Harper <ryanh us ibm com>
---
Changes since v3:
 - Renamed DriveUnplug -> DriveDel, use drive_del monitor cmd.
 - Moved invocation to after DelDevice and guest notification.
 - Handle the case where drive is auto-deleted before we call
   DriveDel by catching and ignoring 'Device not found' error.
 - Simplified DriveDel invocation; no need to check return codes
   as the monitor implementations handle all failure case and logs
   or ignores as needed.
Changes since v2:
 - use VIR_ERROR to report when unplug command not found
Changes since v1:
 - return > 0 when command isn't present, < 0 on command failure
 - detect when drive_unplug command isn't present and log error
   instead of failing entire command

 src/qemu/qemu_driver.c       |   29 ++++++++++++++++++++++
 src/qemu/qemu_monitor.c      |   19 ++++++++++++++
 src/qemu/qemu_monitor.h      |    3 ++
 src/qemu/qemu_monitor_json.c |   38 +++++++++++++++++++++++++++++
 src/qemu/qemu_monitor_json.h |    3 ++
 src/qemu/qemu_monitor_text.c |   54 ++++++++++++++++++++++++++++++++++++++++++
 src/qemu/qemu_monitor_text.h |    3 ++
 7 files changed, 149 insertions(+), 0 deletions(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index e7b37e1..d01bb2c 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -9037,6 +9037,7 @@ static int qemudDomainDetachPciDiskDevice(struct qemud_driver *driver,
     virDomainDiskDefPtr detach = NULL;
     qemuDomainObjPrivatePtr priv = vm->privateData;
     virCgroupPtr cgroup = NULL;
+    char drivestr[PATH_MAX];
 
     i = qemudFindDisk(vm->def, dev->data.disk->dst);
 
@@ -9077,6 +9078,20 @@ static int qemudDomainDetachPciDiskDevice(struct qemud_driver *driver,
             goto cleanup;
         }
     }
+
+    /* build the actual drive id string as the disk->info.alias doesn't
+     * contain the QEMU_DRIVE_HOST_PREFIX that is passed to qemu */
+    if ((ret = snprintf(drivestr, sizeof(drivestr), "%s%s",
+                   QEMU_DRIVE_HOST_PREFIX,
+                   detach->info.alias))
+        < 0 || ret >= sizeof(drivestr)) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    /* disconnect guest from host device */
+    qemuMonitorDriveDel(priv->mon, drivestr);
+
     qemuDomainObjExitMonitorWithDriver(driver, vm);
 
     qemuDomainDiskAudit(vm, detach, NULL, "detach", ret >= 0);
@@ -9116,6 +9131,7 @@ static int qemudDomainDetachSCSIDiskDevice(struct qemud_driver *driver,
     virDomainDiskDefPtr detach = NULL;
     qemuDomainObjPrivatePtr priv = vm->privateData;
     virCgroupPtr cgroup = NULL;
+    char drivestr[PATH_MAX];
 
     i = qemudFindDisk(vm->def, dev->data.disk->dst);
 
@@ -9147,6 +9163,19 @@ static int qemudDomainDetachSCSIDiskDevice(struct qemud_driver *driver,
         qemuDomainObjExitMonitor(vm);
         goto cleanup;
     }
+
+    /* build the actual drive id string as the disk->info.alias doesn't
+     * contain the QEMU_DRIVE_HOST_PREFIX that is passed to qemu */
+    if ((ret = snprintf(drivestr, sizeof(drivestr), "%s%s",
+                   QEMU_DRIVE_HOST_PREFIX,
+                   detach->info.alias))
+        < 0 || ret >= sizeof(drivestr)) {
+        virReportOOMError();
+        goto cleanup;
+    }
+    /* disconnect guest from host device */
+    qemuMonitorDriveDel(priv->mon, drivestr);
+
     qemuDomainObjExitMonitorWithDriver(driver, vm);
 
     qemuDomainDiskAudit(vm, detach, NULL, "detach", ret >= 0);
diff --git a/src/qemu/qemu_monitor.c b/src/qemu/qemu_monitor.c
index 2366fdb..80adba4 100644
--- a/src/qemu/qemu_monitor.c
+++ b/src/qemu/qemu_monitor.c
@@ -1781,6 +1781,25 @@ int qemuMonitorGetAllPCIAddresses(qemuMonitorPtr mon,
     return ret;
 }
 
+int qemuMonitorDriveDel(qemuMonitorPtr mon,
+                        const char *drivestr)
+{
+    DEBUG("mon=%p drivestr=%s", mon, drivestr);
+    int ret;
+
+    if (!mon) {
+        qemuReportError(VIR_ERR_INVALID_ARG, "%s",
+                        _("monitor must not be NULL"));
+        return -1;
+    }
+
+    if (mon->json)
+        ret = qemuMonitorJSONDriveDel(mon, drivestr);
+    else
+        ret = qemuMonitorTextDriveDel(mon, drivestr);
+    return ret;
+}
+
 int qemuMonitorDelDevice(qemuMonitorPtr mon,
                          const char *devalias)
 {
diff --git a/src/qemu/qemu_monitor.h b/src/qemu/qemu_monitor.h
index 7d09145..8cda43b 100644
--- a/src/qemu/qemu_monitor.h
+++ b/src/qemu/qemu_monitor.h
@@ -381,6 +381,9 @@ int qemuMonitorDelDevice(qemuMonitorPtr mon,
 int qemuMonitorAddDrive(qemuMonitorPtr mon,
                         const char *drivestr);
 
+int qemuMonitorDriveDel(qemuMonitorPtr mon,
+                        const char *drivestr);
+
 int qemuMonitorSetDrivePassphrase(qemuMonitorPtr mon,
                                   const char *alias,
                                   const char *passphrase);
diff --git a/src/qemu/qemu_monitor_json.c b/src/qemu/qemu_monitor_json.c
index d2c6f0a..a380ab2 100644
--- a/src/qemu/qemu_monitor_json.c
+++ b/src/qemu/qemu_monitor_json.c
@@ -2244,6 +2244,44 @@ int qemuMonitorJSONAddDrive(qemuMonitorPtr mon,
 }
 
 
+int qemuMonitorJSONDriveDel(qemuMonitorPtr mon,
+                             const char *drivestr)
+{
+    int ret;
+    virJSONValuePtr cmd;
+    virJSONValuePtr reply = NULL;
+
+    DEBUG("JSONDriveDel drivestr=%s", drivestr);
+    cmd = qemuMonitorJSONMakeCommand("drive_del",
+                                     "s:id", drivestr,
+                                     NULL);
+    if (!cmd)
+        return -1;
+
+    ret = qemuMonitorJSONCommand(mon, cmd, &reply);
+
+    if (ret == 0) {
+        /* See if drive_del isn't supported */
+        if (qemuMonitorJSONHasError(reply, "CommandNotFound")) {
+            VIR_ERROR0(_("deleting disk is not supported.  "
+                        "This may leak data if disk is reassigned"));
+            ret = 1;
+            goto cleanup;
+        } else if (qemuMonitorJSONHasError(reply, "DeviceNotFound")) {
+            /* NB: device not found errors mean the drive was 
+             * auto-deleted and we ignore the error */
+            ret = 0;
+        } else {
+            ret = qemuMonitorJSONCheckError(cmd, reply);
+        }
+    }
+
+cleanup:
+    virJSONValueFree(cmd);
+    virJSONValueFree(reply);
+    return ret;
+}
+
 int qemuMonitorJSONSetDrivePassphrase(qemuMonitorPtr mon,
                                       const char *alias,
                                       const char *passphrase)
diff --git a/src/qemu/qemu_monitor_json.h b/src/qemu/qemu_monitor_json.h
index 94806c1..82671c7 100644
--- a/src/qemu/qemu_monitor_json.h
+++ b/src/qemu/qemu_monitor_json.h
@@ -188,6 +188,9 @@ int qemuMonitorJSONDelDevice(qemuMonitorPtr mon,
 int qemuMonitorJSONAddDrive(qemuMonitorPtr mon,
                             const char *drivestr);
 
+int qemuMonitorJSONDriveDel(qemuMonitorPtr mon,
+                            const char *drivestr);
+
 int qemuMonitorJSONSetDrivePassphrase(qemuMonitorPtr mon,
                                       const char *alias,
                                       const char *passphrase);
diff --git a/src/qemu/qemu_monitor_text.c b/src/qemu/qemu_monitor_text.c
index 7f15008..483ceb0 100644
--- a/src/qemu/qemu_monitor_text.c
+++ b/src/qemu/qemu_monitor_text.c
@@ -2285,6 +2285,7 @@ int qemuMonitorTextDelDevice(qemuMonitorPtr mon,
         goto cleanup;
     }
 
+    DEBUG("TextDelDevice devalias=%s", devalias);
     if (qemuMonitorCommand(mon, cmd, &reply) < 0) {
         qemuReportError(VIR_ERR_OPERATION_FAILED,
                         _("cannot detach %s device"), devalias);
@@ -2391,6 +2392,59 @@ cleanup:
     return ret;
 }
 
+/* Attempts to remove a host drive.  
+ * Returns 1 if unsupported, 0 if ok, and -1 on other failure */
+int qemuMonitorTextDriveDel(qemuMonitorPtr mon,
+                             const char *drivestr)
+{
+    char *cmd = NULL;
+    char *reply = NULL;
+    char *safedev;
+    int ret = -1;
+    DEBUG("TextDriveDel drivestr=%s", drivestr);
+
+    if (!(safedev = qemuMonitorEscapeArg(drivestr))) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    if (virAsprintf(&cmd, "drive_del %s", safedev) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
+
+    if (qemuMonitorCommand(mon, cmd, &reply) < 0) {
+        qemuReportError(VIR_ERR_OPERATION_FAILED,
+                        _("cannot delete %s drive"), drivestr);
+        goto cleanup;
+    }
+
+    if (strstr(reply, "unknown command:")) {
+        VIR_ERROR0(_("deleting drive is not supported.  "
+                    "This may leak data if disk is reassigned"));
+        ret = 1;
+        goto cleanup;
+
+    /* (qemu) drive_del wark
+     * Device 'wark' not found */
+    } else if (STRPREFIX(reply, "Device '") && (strstr(reply, "not found"))) {
+        /* NB: device not found errors mean the drive was auto-deleted and we 
+         * ignore the error */
+        ret = 0;
+    } else if (STRNEQ(reply, "")) {
+        qemuReportError(VIR_ERR_OPERATION_FAILED,
+                        _("deleting %s drive failed: %s"), drivestr, reply);
+        goto cleanup;
+    }
+
+    ret = 0;
+
+cleanup:
+    VIR_FREE(cmd);
+    VIR_FREE(reply);
+    VIR_FREE(safedev);
+    return ret;
+}
 
 int qemuMonitorTextSetDrivePassphrase(qemuMonitorPtr mon,
                                       const char *alias,
diff --git a/src/qemu/qemu_monitor_text.h b/src/qemu/qemu_monitor_text.h
index c017509..3a88f87 100644
--- a/src/qemu/qemu_monitor_text.h
+++ b/src/qemu/qemu_monitor_text.h
@@ -186,6 +186,9 @@ int qemuMonitorTextDelDevice(qemuMonitorPtr mon,
 int qemuMonitorTextAddDrive(qemuMonitorPtr mon,
                              const char *drivestr);
 
+int qemuMonitorTextDriveDel(qemuMonitorPtr mon,
+                             const char *drivestr);
+
 int qemuMonitorTextSetDrivePassphrase(qemuMonitorPtr mon,
                                       const char *alias,
                                       const char *passphrase);
-- 
1.6.3.3



-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh us ibm com


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