[PATCH v4 2/8] virCommand: Introduce APIs for core scheduling
There are two modes of core scheduling that are handy wrt
virCommand:
1) create new trusted group when executing a virCommand
2) place freshly executed virCommand into the trusted group of
another process.
Therefore, implement these two new operations as new APIs:
virCommandSetRunAlone() and virCommandSetRunAmong(),
respectively.
Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange(a)redhat.com>
---
src/libvirt_private.syms | 2 ++
src/util/vircommand.c | 63 ++++++++++++++++++++++++++++++++++++++++
src/util/vircommand.h | 5 ++++
3 files changed, 70 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 23abf663f6..02d1c753a4 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -2103,6 +2103,8 @@ virCommandSetOutputBuffer;
virCommandSetOutputFD;
virCommandSetPidFile;
virCommandSetPreExecHook;
+virCommandSetRunAlone;
+virCommandSetRunAmong;
virCommandSetSELinuxLabel;
virCommandSetSendBuffer;
virCommandSetUID;
diff --git a/src/util/vircommand.c b/src/util/vircommand.c
index 4e003266bf..bbfbe19706 100644
--- a/src/util/vircommand.c
+++ b/src/util/vircommand.c
@@ -148,6 +148,13 @@ struct _virCommand {
#endif
int mask;
+ /* schedCore values:
+ * 0: no core scheduling
+ * >0: copy scheduling group from PID
+ * -1: create new scheduling group
+ */
+ pid_t schedCore;
+
virCommandSendBuffer *sendBuffers;
size_t numSendBuffers;
};
@@ -434,6 +441,22 @@ virCommandHandshakeChild(virCommand *cmd)
static int
virExecCommon(virCommand *cmd, gid_t *groups, int ngroups)
{
+ /* Do this before dropping capabilities. */
+ if (cmd->schedCore == -1 &&
+ virProcessSchedCoreCreate() < 0) {
+ virReportSystemError(errno, "%s",
+ _("Unable to set SCHED_CORE"));
+ return -1;
+ }
+
+ if (cmd->schedCore > 0 &&
+ virProcessSchedCoreShareFrom(cmd->schedCore) < 0) {
+ virReportSystemError(errno,
+ _("Unable to run among %llu"),
+ (unsigned long long) cmd->schedCore);
+ return -1;
+ }
+
if (cmd->uid != (uid_t)-1 || cmd->gid != (gid_t)-1 ||
cmd->capabilities || (cmd->flags & VIR_EXEC_CLEAR_CAPS)) {
VIR_DEBUG("Setting child uid:gid to %d:%d with caps %llx",
@@ -3388,3 +3411,43 @@ virCommandRunNul(virCommand *cmd G_GNUC_UNUSED,
return -1;
}
#endif /* WIN32 */
+
+/**
+ * virCommandSetRunAlone:
+ *
+ * Create new trusted group when running the command. In other words, the
+ * process won't be scheduled to run on a core among with processes from
+ * another, untrusted group.
+ */
+void
+virCommandSetRunAlone(virCommand *cmd)
+{
+ if (virCommandHasError(cmd))
+ return;
+
+ cmd->schedCore = -1;
+}
+
+/**
+ * virCommandSetRunAmong:
+ * @pid: pid from a trusted group
+ *
+ * When spawning the command place it into the trusted group of @pid so that
+ * these two processes can run on Hyper Threads of a single core at the same
+ * time.
+ */
+void
+virCommandSetRunAmong(virCommand *cmd,
+ pid_t pid)
+{
+ if (virCommandHasError(cmd))
+ return;
+
+ if (pid <= 0) {
+ VIR_DEBUG("invalid pid value: %lld", (long long) pid);
+ cmd->has_error = -1;
+ return;
+ }
+
+ cmd->schedCore = pid;
+}
diff --git a/src/util/vircommand.h b/src/util/vircommand.h
index c7a580e152..98788bcbf7 100644
--- a/src/util/vircommand.h
+++ b/src/util/vircommand.h
@@ -217,4 +217,9 @@ int virCommandRunNul(virCommand *cmd,
virCommandRunNulFunc func,
void *data);
+void virCommandSetRunAlone(virCommand *cmd);
+
+void virCommandSetRunAmong(virCommand *cmd,
+ pid_t pid);
+
G_DEFINE_AUTOPTR_CLEANUP_FUNC(virCommand, virCommandFree);
--
2.35.1