Re: [PATCH RFC 07/10] 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&gt; --- src/libvirt_private.syms | 2 ++ src/util/vircommand.c | 74 ++++++++++++++++++++++++++++++++++++++++ src/util/vircommand.h | 5 +++ 3 files changed, 81 insertions(+) diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index 252d7e029f..8f2b789cee 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -2079,6 +2079,8 @@ virCommandSetOutputBuffer; virCommandSetOutputFD; virCommandSetPidFile; virCommandSetPreExecHook; +virCommandSetRunAlone; +virCommandSetRunAmong; virCommandSetSELinuxLabel; virCommandSetSendBuffer; virCommandSetUID; diff --git a/src/util/vircommand.c b/src/util/vircommand.c index 41cf552d7b..db20620f7c 100644 --- a/src/util/vircommand.c +++ b/src/util/vircommand.c @@ -148,6 +148,9 @@ struct _virCommand { #endif int mask; + bool schedCore; + pid_t schedCorePID; + virCommandSendBuffer *sendBuffers; size_t numSendBuffers; }; @@ -434,6 +437,22 @@ virCommandHandshakeChild(virCommand *cmd) static int virExecCommon(virCommand *cmd, gid_t *groups, int ngroups) { + /* Do this before dropping capabilities. */ + if (cmd->schedCore && + virProcessSchedCoreCreate() < 0) { + virReportSystemError(errno, "%s", + _("Unable to set SCHED_CORE")); + return -1; + } + + if (cmd->schedCorePID >= 0 && + virProcessSchedCoreShareFrom(cmd->schedCorePID) < 0) { + virReportSystemError(errno, + _("Unable to run among %llu"), + (unsigned long long) cmd->schedCorePID); + 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", @@ -964,6 +983,7 @@ virCommandNewArgs(const char *const*args) cmd->pid = -1; cmd->uid = -1; cmd->gid = -1; + cmd->schedCorePID = -1; virCommandAddArgSet(cmd, args); @@ -3437,3 +3457,57 @@ 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; + + if (cmd->schedCorePID >= 0) { + /* Can't mix these two. */ + cmd->has_error = -1; + VIR_DEBUG("cannot mix with virCommandSetRunAmong()"); + return; + } + + cmd->schedCore = true; +} + +/** + * 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 (cmd->schedCore) { + /* Can't mix these two. */ + VIR_DEBUG("cannot mix with virCommandSetRunAlone()"); + cmd->has_error = -1; + return; + } + + if (pid < 0) { + VIR_DEBUG("invalid pid value: %lld", (long long) pid); + cmd->has_error = -1; + return; + } + + cmd->schedCorePID = pid; +}

1 == copy scheduling group from said PID