[PATCH 4/4] qemu: Open chardev logfile on behalf of QEMU

[Michal Privoznik]

If the QEMU driver is configured to use the old "file" stdio
handler (meaning virtlogd is out of the picture) and a chardev
has a log file configured we rely on QEMU being able to create
the file itself. This may not be always possible (e.g. if the
logfile is set to a directory that QEMU process can't reach).
In such case we should create the file and just pass its FD to
QEMU.

We could do that unconditionally and just either pass FD from
virtlogd or the one we opened, because we bumped QEMU version
and are now requiring new enough QEMU. However, I'm keeping the
old style where logfile is appended on the cmd line for the tests
sake.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1989457
Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---

I don't like the typecast in qemuSecuritySetImageFDLabel() call, but
fixing that turned out to be not trivial, so I left it as is.

 src/qemu/qemu_command.c | 68 ++++++++++++++++++++++++++++++-----------
 1 file changed, 51 insertions(+), 17 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 4381ea7d8b..3aca2bb177 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4702,30 +4702,63 @@ qemuBuildSCSIHostdevDevStr(const virDomainDef *def,
 
 static int
 qemuBuildChrChardevFileStr(virLogManager *logManager,
-                           virCommand *cmd,
+                           virSecurityManager *secManager,
+                           virQEMUDriverConfig *cfg,
+                           virQEMUCaps *qemuCaps,
                            const virDomainDef *def,
+                           virCommand *cmd,
                            virBuffer *buf,
                            const char *filearg, const char *fileval,
                            const char *appendarg, int appendval)
 {
-    if (logManager) {
+    /* Technically, to pass an FD via /dev/fdset we don't need
+     * any capability check because X_QEMU_CAPS_ADD_FD is already
+     * assumed. But keeping the old style is still handy when
+     * building a standalone command line (e.g. for tests). */
+    if (logManager ||
+        virQEMUCapsGet(qemuCaps, QEMU_CAPS_CHARDEV_FD_PASS)) {
         g_autofree char *fdset = NULL;
-        int flags = 0;
         int logfd;
         size_t idx;
 
-        if (appendval == VIR_TRISTATE_SWITCH_ABSENT ||
-            appendval == VIR_TRISTATE_SWITCH_OFF)
-            flags |= VIR_LOG_MANAGER_PROTOCOL_DOMAIN_OPEN_LOG_FILE_TRUNCATE;
-
-        if ((logfd = virLogManagerDomainOpenLogFile(logManager,
-                                                    "qemu",
-                                                    def->uuid,
-                                                    def->name,
-                                                    fileval,
-                                                    flags,
-                                                    NULL, NULL)) < 0)
-            return -1;
+        if (logManager) {
+            int flags = 0;
+
+            if (appendval == VIR_TRISTATE_SWITCH_ABSENT ||
+                appendval == VIR_TRISTATE_SWITCH_OFF)
+                flags |= VIR_LOG_MANAGER_PROTOCOL_DOMAIN_OPEN_LOG_FILE_TRUNCATE;
+
+            if ((logfd = virLogManagerDomainOpenLogFile(logManager,
+                                                        "qemu",
+                                                        def->uuid,
+                                                        def->name,
+                                                        fileval,
+                                                        flags,
+                                                        NULL, NULL)) < 0)
+                return -1;
+        } else {
+            int oflags = O_CREAT | O_WRONLY;
+
+            switch (appendval) {
+            case VIR_TRISTATE_SWITCH_ABSENT:
+            case VIR_TRISTATE_SWITCH_OFF:
+                oflags |= O_TRUNC;
+                break;
+            case VIR_TRISTATE_SWITCH_ON:
+                oflags |= O_APPEND;
+                break;
+            case VIR_TRISTATE_SWITCH_LAST:
+                break;
+            }
+
+            if ((logfd = qemuDomainOpenFile(cfg, def, fileval, oflags, NULL)) < 0)
+                return -1;
+
+            if (qemuSecuritySetImageFDLabel(secManager, (virDomainDef*)def, logfd) < 0) {
+                VIR_FORCE_CLOSE(logfd);
+                return -1;
+            }
+        }
 
         virCommandPassFDIndex(cmd, logfd, VIR_COMMAND_PASS_FD_CLOSE_PARENT, &idx);
         fdset = qemuBuildFDSet(logfd, idx);
@@ -4868,7 +4901,7 @@ qemuBuildChrChardevStr(virLogManager *logManager,
 
         if (qemuBuildChrChardevFileStr(cdevflags & QEMU_BUILD_CHARDEV_FILE_LOGD ?
                                        logManager : NULL,
-                                       cmd, def, &buf,
+                                       secManager, cfg, qemuCaps, def, cmd, &buf,
                                        "path", dev->data.file.path,
                                        "append", dev->data.file.append) < 0)
             return NULL;
@@ -5004,7 +5037,8 @@ qemuBuildChrChardevStr(virLogManager *logManager,
     }
 
     if (dev->logfile) {
-        if (qemuBuildChrChardevFileStr(logManager, cmd, def, &buf,
+        if (qemuBuildChrChardevFileStr(logManager, secManager, cfg,
+                                       qemuCaps, def, cmd, &buf,
                                        "logfile", dev->logfile,
                                        "logappend", dev->logappend) < 0)
             return NULL;
-- 
2.31.1