| Message ID | 20231031144605.64822-3-aharivel@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Add support for RAPL MSRs series | expand |
On Tue, Oct 31, 2023 at 03:46:02PM +0100, Anthony Harivel wrote: > Introduce a privileged helper to access RAPL MSR. > > The privileged helper tool, qemu-vmsr-helper, is designed to provide > virtual machines with the ability to read specific RAPL (Running Average > Power Limit) MSRs without requiring CAP_SYS_RAWIO privileges or relying > on external, out-of-tree patches. > > The helper tool leverages Unix permissions and SO_PEERCRED socket > options to enforce access control, ensuring that only processes > explicitly requesting read access via readmsr() from a valid Thread ID > can access these MSRs. > > The list of RAPL MSRs that are allowed to be read by the helper tool is > defined in rapl-msr-index.h. This list corresponds to the RAPL MSRs that > will be supported in the next commit titled "Add support for RAPL MSRs > in KVM/QEMU." > > Signed-off-by: Anthony Harivel <aharivel@redhat.com> > --- > docs/tools/index.rst | 1 + > docs/tools/qemu-vmsr-helper.rst | 89 ++++++ > meson.build | 5 + > tools/i386/qemu-vmsr-helper.c | 507 ++++++++++++++++++++++++++++++++ > tools/i386/rapl-msr-index.h | 28 ++ Missing .service and .socket unit files needed for systemd integration. See those present for qemu-pr-helper for examples > 5 files changed, 630 insertions(+) > create mode 100644 docs/tools/qemu-vmsr-helper.rst > create mode 100644 tools/i386/qemu-vmsr-helper.c > create mode 100644 tools/i386/rapl-msr-index.h > diff --git a/tools/i386/qemu-vmsr-helper.c b/tools/i386/qemu-vmsr-helper.c > new file mode 100644 > index 000000000000..1d82a2753e44 > --- /dev/null > +++ b/tools/i386/qemu-vmsr-helper.c > +#define MAX_PATH_LEN 50 > +#define MAX_LINE_LEN 500 > +#define PR_OUT_FIXED_PARAM_SIZE 24 These latter two constants are not used. > + > +static char *socket_path; > +static char *pidfile; > +static enum { RUNNING, TERMINATE, TERMINATING } state; > +static QIOChannelSocket *server_ioc; > +static int server_watch; > +static int num_active_sockets = 1; > +static int noisy; > +static int verbose; > + > +#ifdef CONFIG_LIBCAP_NG > +static int uid = -1; > +static int gid = -1; > +#endif > + > +static void compute_default_paths(void) > +{ > + g_autofree char *state = qemu_get_local_state_dir(); > + > + socket_path = g_build_filename(state, "run", "qemu-vmsr-helper.sock", NULL); > + pidfile = g_build_filename(state, "run", "qemu-vmsr-helper.pid", NULL); > +} > + > +/* > + * Check if the TID that request the MSR read > + * belongs to the peer. It should a TID of a vCPU. > + */ > +static bool is_tid_present(pid_t pid, pid_t tid) > +{ > + char pidStr[20]; > + char tidStr[20]; > + > + snprintf(pidStr, sizeof(pidStr), "%d", pid); > + snprintf(tidStr, sizeof(tidStr), "%d", tid); g_strdup_printf() not an unchecked static buffer. > + > + char pidPath[256]; > + char tidPath[256]; > + > + snprintf(pidPath, sizeof(pidPath), "/proc/%s", pidStr); You never read this variable once built > + snprintf(tidPath, sizeof(tidPath), "/proc/%s/task/%s", pidStr, tidStr); g_build_file_name > + > + /* Check if the TID directory exists within the PID directory */ > + if (access(tidPath, F_OK) == 0) { > + return true; > + } > + > + return false; > +} > +static uint64_t vmsr_read_msr(uint32_t reg, unsigned int cpu_id) > +{ > + int fd; > + uint64_t data; > + > + char path[MAX_PATH_LEN]; > + snprintf(path, MAX_PATH_LEN, "/dev/cpu/%u/msr", cpu_id); g_strdup_printf > + > + fd = open(path , O_RDONLY); > + if (fd < 0) { > + return 0; > + } > + if (pread(fd, &data, sizeof data, reg) != sizeof data) { > + data = 0; > + } > + > + close(fd); > + return data; > +} > + > +static void usage(const char *name) > +{ > + (printf) ( > +"Usage: %s [OPTIONS] FILE\n" > +"Virtual RAPL MSR helper program for QEMU\n" > +"\n" > +" -h, --help display this help and exit\n" > +" -V, --version output version information and exit\n" > +"\n" > +" -d, --daemon run in the background\n" > +" -f, --pidfile=PATH PID file when running as a daemon\n" > +" (default '%s')\n" > +" -k, --socket=PATH path to the unix socket\n" > +" (default '%s')\n" > +" -T, --trace [[enable=]<pattern>][,events=<file>][,file=<file>]\n" > +" specify tracing options\n" > +#ifdef CONFIG_LIBCAP_NG > +" -u, --user=USER user to drop privileges to\n" > +" -g, --group=GROUP group to drop privileges to\n" > +#endif > +"\n" > +QEMU_HELP_BOTTOM "\n" > + , name, pidfile, socket_path); > +} > + > +static void version(const char *name) > +{ > + printf( > +"%s " QEMU_FULL_VERSION "\n" > +"Written by Anthony Harivel.\n" > +"\n" > +QEMU_COPYRIGHT "\n" > +"This is free software; see the source for copying conditions. There is NO\n" > +"warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n" > + , name); > +} > + > +typedef struct VMSRHelperClient { > + QIOChannelSocket *ioc; > + Coroutine *co; > + int fd; This FD field is set to -1 and never changed / read thereafter AFAICS, so please remove it. > +} VMSRHelperClient; > + > +static void coroutine_fn vh_co_entry(void *opaque) > +{ > + VMSRHelperClient *client = opaque; > + uint64_t vmsr; > + uint32_t request[3]; > + struct ucred cred; > + int r; > + Error *local_err = NULL; > + > + qio_channel_set_blocking(QIO_CHANNEL(client->ioc), > + false, NULL); > + > + qio_channel_set_follow_coroutine_ctx(QIO_CHANNEL(client->ioc), true); > + > + /* > + * Check peer credentials > + * Only QEMU PID/TID are allowed > + */ > + qio_channel_get_peercred(QIO_CHANNEL(client->ioc), &cred, &local_err); > + > + if (cred.pid == 0) { > + if (local_err != NULL) { > + error_report_err(local_err); > + } > + error_report("Failed to get peer credentials"); > + goto out; > + } > + > + /* > + * Read the requested MSR > + * Only RAPL MSR in rapl-msr-index.h is allowed > + */ > + r = qio_channel_read_all(QIO_CHANNEL(client->ioc), > + (char *) &request, sizeof(request), NULL); The 'NULL' should be &local_err, so that the next error_report line actually gives a useful error message with actual details. > + if (!is_msr_allowed(request[0]) || r < 0) { request[0] is accessing uninitialized memory in case that r < 0. You must check for errors first. > + error_report("Read request fail: %d, %d", request[0], request[1]); use error_report_err in the 'r < 0' case. > + goto out; > + } > + > + vmsr = vmsr_read_msr(request[0], request[1]); > + > + if (!is_tid_present(cred.pid, request[2])) { > + error_report("requested TID not in peer PID"); > + vmsr = 0; > + } > + > + r = qio_channel_write_all(QIO_CHANNEL(client->ioc), > + (char *) &vmsr, sizeof(vmsr), NULL); Again you must pass &local_err... > + if (r < 0) { > + error_report("write vmsr failed"); and use error_report_err > + goto out; > + } > + > +out: > + object_unref(OBJECT(client->ioc)); > + g_free(client); > +} > + > +static gboolean accept_client(QIOChannel *ioc, > + GIOCondition cond, > + gpointer opaque) > +{ > + QIOChannelSocket *cioc; > + VMSRHelperClient *vmsrh; > + > + cioc = qio_channel_socket_accept(QIO_CHANNEL_SOCKET(ioc), > + NULL); > + if (!cioc) { > + return TRUE; > + } > + > + vmsrh = g_new(VMSRHelperClient, 1); > + vmsrh->ioc = cioc; > + vmsrh->fd = -1; > + vmsrh->co = qemu_coroutine_create(vh_co_entry, vmsrh); > + qemu_coroutine_enter(vmsrh->co); > + > + return TRUE; > +} > + > +static void termsig_handler(int signum) > +{ > + qatomic_cmpxchg(&state, RUNNING, TERMINATE); > + qemu_notify_event(); > +} > + > +static void close_server_socket(void) > +{ > + assert(server_ioc); > + > + g_source_remove(server_watch); > + server_watch = -1; > + object_unref(OBJECT(server_ioc)); > + num_active_sockets--; > +} > + > +#ifdef CONFIG_LIBCAP_NG > +static int drop_privileges(void) > +{ > + /* clear all capabilities */ > + capng_clear(CAPNG_SELECT_BOTH); > + > + if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED, > + CAP_SYS_RAWIO) < 0) { > + return -1; > + } > + > + /* > + * Change user/group id, retaining the capabilities. > + * Because file descriptors are passed via SCM_RIGHTS, > + * we don't need supplementary groups (and in fact the helper > + * can run as "nobody"). > + */ > + if (capng_change_id(uid != -1 ? uid : getuid(), > + gid != -1 ? gid : getgid(), > + CAPNG_DROP_SUPP_GRP | CAPNG_CLEAR_BOUNDING)) { > + return -1; > + } > + > + return 0; > +} > +#endif > + > +int main(int argc, char **argv) > +{ > + const char *sopt = "hVk:f:dT:u:g:vq"; > + struct option lopt[] = { > + { "help", no_argument, NULL, 'h' }, > + { "version", no_argument, NULL, 'V' }, > + { "socket", required_argument, NULL, 'k' }, > + { "pidfile", required_argument, NULL, 'f' }, > + { "daemon", no_argument, NULL, 'd' }, > + { "trace", required_argument, NULL, 'T' }, > + { "user", required_argument, NULL, 'u' }, > + { "group", required_argument, NULL, 'g' }, > + { "verbose", no_argument, NULL, 'v' }, > + { "quiet", no_argument, NULL, 'q' }, > + { NULL, 0, NULL, 0 } > + }; > + int opt_ind = 0; > + int loglevel = 1; > + int quiet = 0; > + int ch; > + Error *local_err = NULL; > + bool daemonize = false; > + bool pidfile_specified = false; > + bool socket_path_specified = false; > + unsigned socket_activation; > + > + struct sigaction sa_sigterm; > + memset(&sa_sigterm, 0, sizeof(sa_sigterm)); > + sa_sigterm.sa_handler = termsig_handler; > + sigaction(SIGTERM, &sa_sigterm, NULL); > + sigaction(SIGINT, &sa_sigterm, NULL); > + sigaction(SIGHUP, &sa_sigterm, NULL); > + > + signal(SIGPIPE, SIG_IGN); > + > + error_init(argv[0]); > + module_call_init(MODULE_INIT_TRACE); > + module_call_init(MODULE_INIT_QOM); > + qemu_add_opts(&qemu_trace_opts); > + qemu_init_exec_dir(argv[0]); > + > + compute_default_paths(); > + > + while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) { > + switch (ch) { > + case 'k': > + g_free(socket_path); > + socket_path = g_strdup(optarg); > + socket_path_specified = true; > + if (socket_path[0] != '/') { > + error_report("socket path must be absolute"); > + exit(EXIT_FAILURE); > + } > + break; > + case 'f': > + g_free(pidfile); > + pidfile = g_strdup(optarg); > + pidfile_specified = true; > + break; > +#ifdef CONFIG_LIBCAP_NG > + case 'u': { > + unsigned long res; > + struct passwd *userinfo = getpwnam(optarg); > + if (userinfo) { > + uid = userinfo->pw_uid; > + } else if (qemu_strtoul(optarg, NULL, 10, &res) == 0 && > + (uid_t)res == res) { > + uid = res; > + } else { > + error_report("invalid user '%s'", optarg); > + exit(EXIT_FAILURE); > + } > + break; > + } > + case 'g': { > + unsigned long res; > + struct group *groupinfo = getgrnam(optarg); > + if (groupinfo) { > + gid = groupinfo->gr_gid; > + } else if (qemu_strtoul(optarg, NULL, 10, &res) == 0 && > + (gid_t)res == res) { > + gid = res; > + } else { > + error_report("invalid group '%s'", optarg); > + exit(EXIT_FAILURE); > + } > + break; > + } > +#else > + case 'u': > + case 'g': > + error_report("-%c not supported by this %s", ch, argv[0]); > + exit(1); > +#endif > + case 'd': > + daemonize = true; > + break; > + case 'q': > + quiet = 1; > + break; > + case 'v': > + ++loglevel; > + break; > + case 'T': > + trace_opt_parse(optarg); > + break; > + case 'V': > + version(argv[0]); > + exit(EXIT_SUCCESS); > + break; > + case 'h': > + usage(argv[0]); > + exit(EXIT_SUCCESS); > + break; > + case '?': > + error_report("Try `%s --help' for more information.", argv[0]); > + exit(EXIT_FAILURE); > + } > + } > + > + /* set verbosity */ > + noisy = !quiet && (loglevel >= 3); > + verbose = quiet ? 0 : MIN(loglevel, 3); AFAIK nothing ever uses the noisy or verbose flags, so please remove them or use them. > + > + if (!trace_init_backends()) { > + exit(EXIT_FAILURE); > + } > + trace_init_file(); > + qemu_set_log(LOG_TRACE, &error_fatal); With regards, Daniel
On Tue, Oct 31, 2023 at 03:46:02PM +0100, Anthony Harivel wrote: > Introduce a privileged helper to access RAPL MSR. > > The privileged helper tool, qemu-vmsr-helper, is designed to provide > virtual machines with the ability to read specific RAPL (Running Average > Power Limit) MSRs without requiring CAP_SYS_RAWIO privileges or relying > on external, out-of-tree patches. > > The helper tool leverages Unix permissions and SO_PEERCRED socket > options to enforce access control, ensuring that only processes > explicitly requesting read access via readmsr() from a valid Thread ID > can access these MSRs. > > The list of RAPL MSRs that are allowed to be read by the helper tool is > defined in rapl-msr-index.h. This list corresponds to the RAPL MSRs that > will be supported in the next commit titled "Add support for RAPL MSRs > in KVM/QEMU." > > Signed-off-by: Anthony Harivel <aharivel@redhat.com> > --- > docs/tools/index.rst | 1 + > docs/tools/qemu-vmsr-helper.rst | 89 ++++++ > meson.build | 5 + > tools/i386/qemu-vmsr-helper.c | 507 ++++++++++++++++++++++++++++++++ > tools/i386/rapl-msr-index.h | 28 ++ > 5 files changed, 630 insertions(+) > create mode 100644 docs/tools/qemu-vmsr-helper.rst > create mode 100644 tools/i386/qemu-vmsr-helper.c > create mode 100644 tools/i386/rapl-msr-index.h > > +/* > + * Check if the TID that request the MSR read > + * belongs to the peer. It should a TID of a vCPU. > + */ > +static bool is_tid_present(pid_t pid, pid_t tid) > +{ > + char pidStr[20]; > + char tidStr[20]; > + > + snprintf(pidStr, sizeof(pidStr), "%d", pid); > + snprintf(tidStr, sizeof(tidStr), "%d", tid); > + > + char pidPath[256]; > + char tidPath[256]; > + > + snprintf(pidPath, sizeof(pidPath), "/proc/%s", pidStr); > + snprintf(tidPath, sizeof(tidPath), "/proc/%s/task/%s", pidStr, tidStr); > + > + /* Check if the TID directory exists within the PID directory */ > + if (access(tidPath, F_OK) == 0) { > + return true; > + } > + > + return false; > +} > + > +/* > + * Only the RAPL MSR in target/i386/cpu.h are allowed > + */ > +static bool is_msr_allowed(uint32_t reg) > +{ > + switch (reg) { > + case MSR_RAPL_POWER_UNIT: > + case MSR_PKG_POWER_LIMIT: > + case MSR_PKG_ENERGY_STATUS: > + case MSR_PKG_POWER_INFO: > + return true; > + default: > + return false; > + } > +} > + /* > + * Check peer credentials > + * Only QEMU PID/TID are allowed This says only QEMU is allowed > + */ > + qio_channel_get_peercred(QIO_CHANNEL(client->ioc), &cred, &local_err); > + > + if (cred.pid == 0) { > + if (local_err != NULL) { > + error_report_err(local_err); > + } > + error_report("Failed to get peer credentials"); > + goto out; > + } > + > + /* > + * Read the requested MSR > + * Only RAPL MSR in rapl-msr-index.h is allowed > + */ > + r = qio_channel_read_all(QIO_CHANNEL(client->ioc), > + (char *) &request, sizeof(request), NULL); > + if (!is_msr_allowed(request[0]) || r < 0) { > + error_report("Read request fail: %d, %d", request[0], request[1]); > + goto out; > + } > + > + vmsr = vmsr_read_msr(request[0], request[1]); > + > + if (!is_tid_present(cred.pid, request[2])) { > + error_report("requested TID not in peer PID"); > + vmsr = 0; > + } This check is merely validating the the thread ID in the message is a child of the process ID connected to the socket. Any process on the entire host can satisfy this requirement. I don't see what is limiting this to only QEMU as claimed earlier, unless you're expecting the UNIX socket permissions to be such that only processes under the qemu:qemu user:group pair can access to the socket ? That would be a libvirt based permissions assumption though. > + > + r = qio_channel_write_all(QIO_CHANNEL(client->ioc), > + (char *) &vmsr, sizeof(vmsr), NULL); > + if (r < 0) { > + error_report("write vmsr failed"); > + goto out; > + } > + > +out: > + object_unref(OBJECT(client->ioc)); > + g_free(client); > +} With regards, Daniel
On 10/31/23 15:46, Anthony Harivel wrote: > + > +static uint64_t vmsr_read_msr(uint32_t reg, unsigned int cpu_id) > +{ > + int fd; > + uint64_t data; > + > + char path[MAX_PATH_LEN]; > + snprintf(path, MAX_PATH_LEN, "/dev/cpu/%u/msr", cpu_id); If you allow any CPU here, the thread id is really unused. You can however call sched_getaffinity(), and check that the CPU id is included in the thread's affinity. sched_getaffinity() does not need any extra capability. Paolo
diff --git a/docs/tools/index.rst b/docs/tools/index.rst index 8e65ce0dfc7b..33ad438e86f6 100644 --- a/docs/tools/index.rst +++ b/docs/tools/index.rst @@ -16,3 +16,4 @@ command line utilities and other standalone programs. qemu-pr-helper qemu-trace-stap virtfs-proxy-helper + qemu-vmsr-helper diff --git a/docs/tools/qemu-vmsr-helper.rst b/docs/tools/qemu-vmsr-helper.rst new file mode 100644 index 000000000000..6ec87b49d962 --- /dev/null +++ b/docs/tools/qemu-vmsr-helper.rst @@ -0,0 +1,89 @@ +================================== +QEMU virtual RAPL MSR helper +================================== + +Synopsis +-------- + +**qemu-vmsr-helper** [*OPTION*] + +Description +----------- + +Implements the virtual RAPL MSR helper for QEMU. + +Accessing the RAPL (Running Average Power Limit) MSR enables the RAPL powercap +driver to advertise and monitor the power consumption or accumulated energy +consumption of different power domains, such as CPU packages, DRAM, and other +components when available. + +However those register are accesible under priviliged access (CAP_SYS_RAWIO). +QEMU can use an external helper to access those priviliged register. + +:program:`qemu-vmsr-helper` is that external helper; it creates a listener +socket which will accept incoming connections for communication with QEMU. + +If you want to run VMs in a setup like this, this helper should be started as a +system service, and you should read the QEMU manual section on "RAPL MSR +support" to find out how to configure QEMU to connect to the socket created by +:program:`qemu-vmsr-helper`. + +After connecting to the socket, :program:`qemu-vmsr-helper` can +optionally drop root privileges, except for those capabilities that +are needed for its operation. + +:program:`qemu-vmsr-helper` can also use the systemd socket activation +protocol. In this case, the systemd socket unit should specify a +Unix stream socket, like this:: + + [Socket] + ListenStream=/var/run/qemu-vmsr-helper.sock + +Options +------- + +.. program:: qemu-vmsr-helper + +.. option:: -d, --daemon + + run in the background (and create a PID file) + +.. option:: -q, --quiet + + decrease verbosity + +.. option:: -v, --verbose + + increase verbosity + +.. option:: -f, --pidfile=PATH + + PID file when running as a daemon. By default the PID file + is created in the system runtime state directory, for example + :file:`/var/run/qemu-vmsr-helper.pid`. + +.. option:: -k, --socket=PATH + + path to the socket. By default the socket is created in + the system runtime state directory, for example + :file:`/var/run/qemu-vmsr-helper.sock`. + +.. option:: -T, --trace [[enable=]PATTERN][,events=FILE][,file=FILE] + + .. include:: ../qemu-option-trace.rst.inc + +.. option:: -u, --user=USER + + user to drop privileges to + +.. option:: -g, --group=GROUP + + group to drop privileges to + +.. option:: -h, --help + + Display a help message and exit. + +.. option:: -V, --version + + Display version information and exit. diff --git a/meson.build b/meson.build index dcef8b1e7911..d30a7a09d46f 100644 --- a/meson.build +++ b/meson.build @@ -3950,6 +3950,11 @@ if have_tools dependencies: [authz, crypto, io, qom, qemuutil, libcap_ng, mpathpersist], install: true) + + executable('qemu-vmsr-helper', files('tools/i386/qemu-vmsr-helper.c'), + dependencies: [authz, crypto, io, qom, qemuutil, + libcap_ng, mpathpersist], + install: true) endif if have_ivshmem diff --git a/tools/i386/qemu-vmsr-helper.c b/tools/i386/qemu-vmsr-helper.c new file mode 100644 index 000000000000..1d82a2753e44 --- /dev/null +++ b/tools/i386/qemu-vmsr-helper.c @@ -0,0 +1,507 @@ +/* + * Privileged RAPL MSR helper commands for QEMU + * + * Copyright (C) 2023 Red Hat, Inc. <aharivel@redhat.com> + * + * Author: Anthony Harivel <aharivel@redhat.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; under version 2 of the License. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +#include "qemu/osdep.h" +#include <getopt.h> +#include <stdbool.h> +#include <sys/ioctl.h> +#ifdef CONFIG_LIBCAP_NG +#include <cap-ng.h> +#endif +#include <pwd.h> +#include <grp.h> + +#include "qemu/help-texts.h" +#include "qapi/error.h" +#include "qemu/cutils.h" +#include "qemu/main-loop.h" +#include "qemu/module.h" +#include "qemu/error-report.h" +#include "qemu/config-file.h" +#include "qemu-version.h" +#include "qapi/error.h" +#include "qemu/error-report.h" +#include "qemu/log.h" +#include "qemu/systemd.h" +#include "qapi/util.h" +#include "io/channel.h" +#include "io/channel-socket.h" +#include "trace/control.h" +#include "qemu-version.h" +#include "rapl-msr-index.h" + +#define MAX_PATH_LEN 50 +#define MAX_LINE_LEN 500 +#define PR_OUT_FIXED_PARAM_SIZE 24 + +static char *socket_path; +static char *pidfile; +static enum { RUNNING, TERMINATE, TERMINATING } state; +static QIOChannelSocket *server_ioc; +static int server_watch; +static int num_active_sockets = 1; +static int noisy; +static int verbose; + +#ifdef CONFIG_LIBCAP_NG +static int uid = -1; +static int gid = -1; +#endif + +static void compute_default_paths(void) +{ + g_autofree char *state = qemu_get_local_state_dir(); + + socket_path = g_build_filename(state, "run", "qemu-vmsr-helper.sock", NULL); + pidfile = g_build_filename(state, "run", "qemu-vmsr-helper.pid", NULL); +} + +/* + * Check if the TID that request the MSR read + * belongs to the peer. It should a TID of a vCPU. + */ +static bool is_tid_present(pid_t pid, pid_t tid) +{ + char pidStr[20]; + char tidStr[20]; + + snprintf(pidStr, sizeof(pidStr), "%d", pid); + snprintf(tidStr, sizeof(tidStr), "%d", tid); + + char pidPath[256]; + char tidPath[256]; + + snprintf(pidPath, sizeof(pidPath), "/proc/%s", pidStr); + snprintf(tidPath, sizeof(tidPath), "/proc/%s/task/%s", pidStr, tidStr); + + /* Check if the TID directory exists within the PID directory */ + if (access(tidPath, F_OK) == 0) { + return true; + } + + return false; +} + +/* + * Only the RAPL MSR in target/i386/cpu.h are allowed + */ +static bool is_msr_allowed(uint32_t reg) +{ + switch (reg) { + case MSR_RAPL_POWER_UNIT: + case MSR_PKG_POWER_LIMIT: + case MSR_PKG_ENERGY_STATUS: + case MSR_PKG_POWER_INFO: + return true; + default: + return false; + } +} + +static uint64_t vmsr_read_msr(uint32_t reg, unsigned int cpu_id) +{ + int fd; + uint64_t data; + + char path[MAX_PATH_LEN]; + snprintf(path, MAX_PATH_LEN, "/dev/cpu/%u/msr", cpu_id); + + fd = open(path , O_RDONLY); + if (fd < 0) { + return 0; + } + if (pread(fd, &data, sizeof data, reg) != sizeof data) { + data = 0; + } + + close(fd); + return data; +} + +static void usage(const char *name) +{ + (printf) ( +"Usage: %s [OPTIONS] FILE\n" +"Virtual RAPL MSR helper program for QEMU\n" +"\n" +" -h, --help display this help and exit\n" +" -V, --version output version information and exit\n" +"\n" +" -d, --daemon run in the background\n" +" -f, --pidfile=PATH PID file when running as a daemon\n" +" (default '%s')\n" +" -k, --socket=PATH path to the unix socket\n" +" (default '%s')\n" +" -T, --trace [[enable=]<pattern>][,events=<file>][,file=<file>]\n" +" specify tracing options\n" +#ifdef CONFIG_LIBCAP_NG +" -u, --user=USER user to drop privileges to\n" +" -g, --group=GROUP group to drop privileges to\n" +#endif +"\n" +QEMU_HELP_BOTTOM "\n" + , name, pidfile, socket_path); +} + +static void version(const char *name) +{ + printf( +"%s " QEMU_FULL_VERSION "\n" +"Written by Anthony Harivel.\n" +"\n" +QEMU_COPYRIGHT "\n" +"This is free software; see the source for copying conditions. There is NO\n" +"warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n" + , name); +} + +typedef struct VMSRHelperClient { + QIOChannelSocket *ioc; + Coroutine *co; + int fd; +} VMSRHelperClient; + +static void coroutine_fn vh_co_entry(void *opaque) +{ + VMSRHelperClient *client = opaque; + uint64_t vmsr; + uint32_t request[3]; + struct ucred cred; + int r; + Error *local_err = NULL; + + qio_channel_set_blocking(QIO_CHANNEL(client->ioc), + false, NULL); + + qio_channel_set_follow_coroutine_ctx(QIO_CHANNEL(client->ioc), true); + + /* + * Check peer credentials + * Only QEMU PID/TID are allowed + */ + qio_channel_get_peercred(QIO_CHANNEL(client->ioc), &cred, &local_err); + + if (cred.pid == 0) { + if (local_err != NULL) { + error_report_err(local_err); + } + error_report("Failed to get peer credentials"); + goto out; + } + + /* + * Read the requested MSR + * Only RAPL MSR in rapl-msr-index.h is allowed + */ + r = qio_channel_read_all(QIO_CHANNEL(client->ioc), + (char *) &request, sizeof(request), NULL); + if (!is_msr_allowed(request[0]) || r < 0) { + error_report("Read request fail: %d, %d", request[0], request[1]); + goto out; + } + + vmsr = vmsr_read_msr(request[0], request[1]); + + if (!is_tid_present(cred.pid, request[2])) { + error_report("requested TID not in peer PID"); + vmsr = 0; + } + + r = qio_channel_write_all(QIO_CHANNEL(client->ioc), + (char *) &vmsr, sizeof(vmsr), NULL); + if (r < 0) { + error_report("write vmsr failed"); + goto out; + } + +out: + object_unref(OBJECT(client->ioc)); + g_free(client); +} + +static gboolean accept_client(QIOChannel *ioc, + GIOCondition cond, + gpointer opaque) +{ + QIOChannelSocket *cioc; + VMSRHelperClient *vmsrh; + + cioc = qio_channel_socket_accept(QIO_CHANNEL_SOCKET(ioc), + NULL); + if (!cioc) { + return TRUE; + } + + vmsrh = g_new(VMSRHelperClient, 1); + vmsrh->ioc = cioc; + vmsrh->fd = -1; + vmsrh->co = qemu_coroutine_create(vh_co_entry, vmsrh); + qemu_coroutine_enter(vmsrh->co); + + return TRUE; +} + +static void termsig_handler(int signum) +{ + qatomic_cmpxchg(&state, RUNNING, TERMINATE); + qemu_notify_event(); +} + +static void close_server_socket(void) +{ + assert(server_ioc); + + g_source_remove(server_watch); + server_watch = -1; + object_unref(OBJECT(server_ioc)); + num_active_sockets--; +} + +#ifdef CONFIG_LIBCAP_NG +static int drop_privileges(void) +{ + /* clear all capabilities */ + capng_clear(CAPNG_SELECT_BOTH); + + if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED, + CAP_SYS_RAWIO) < 0) { + return -1; + } + + /* + * Change user/group id, retaining the capabilities. + * Because file descriptors are passed via SCM_RIGHTS, + * we don't need supplementary groups (and in fact the helper + * can run as "nobody"). + */ + if (capng_change_id(uid != -1 ? uid : getuid(), + gid != -1 ? gid : getgid(), + CAPNG_DROP_SUPP_GRP | CAPNG_CLEAR_BOUNDING)) { + return -1; + } + + return 0; +} +#endif + +int main(int argc, char **argv) +{ + const char *sopt = "hVk:f:dT:u:g:vq"; + struct option lopt[] = { + { "help", no_argument, NULL, 'h' }, + { "version", no_argument, NULL, 'V' }, + { "socket", required_argument, NULL, 'k' }, + { "pidfile", required_argument, NULL, 'f' }, + { "daemon", no_argument, NULL, 'd' }, + { "trace", required_argument, NULL, 'T' }, + { "user", required_argument, NULL, 'u' }, + { "group", required_argument, NULL, 'g' }, + { "verbose", no_argument, NULL, 'v' }, + { "quiet", no_argument, NULL, 'q' }, + { NULL, 0, NULL, 0 } + }; + int opt_ind = 0; + int loglevel = 1; + int quiet = 0; + int ch; + Error *local_err = NULL; + bool daemonize = false; + bool pidfile_specified = false; + bool socket_path_specified = false; + unsigned socket_activation; + + struct sigaction sa_sigterm; + memset(&sa_sigterm, 0, sizeof(sa_sigterm)); + sa_sigterm.sa_handler = termsig_handler; + sigaction(SIGTERM, &sa_sigterm, NULL); + sigaction(SIGINT, &sa_sigterm, NULL); + sigaction(SIGHUP, &sa_sigterm, NULL); + + signal(SIGPIPE, SIG_IGN); + + error_init(argv[0]); + module_call_init(MODULE_INIT_TRACE); + module_call_init(MODULE_INIT_QOM); + qemu_add_opts(&qemu_trace_opts); + qemu_init_exec_dir(argv[0]); + + compute_default_paths(); + + while ((ch = getopt_long(argc, argv, sopt, lopt, &opt_ind)) != -1) { + switch (ch) { + case 'k': + g_free(socket_path); + socket_path = g_strdup(optarg); + socket_path_specified = true; + if (socket_path[0] != '/') { + error_report("socket path must be absolute"); + exit(EXIT_FAILURE); + } + break; + case 'f': + g_free(pidfile); + pidfile = g_strdup(optarg); + pidfile_specified = true; + break; +#ifdef CONFIG_LIBCAP_NG + case 'u': { + unsigned long res; + struct passwd *userinfo = getpwnam(optarg); + if (userinfo) { + uid = userinfo->pw_uid; + } else if (qemu_strtoul(optarg, NULL, 10, &res) == 0 && + (uid_t)res == res) { + uid = res; + } else { + error_report("invalid user '%s'", optarg); + exit(EXIT_FAILURE); + } + break; + } + case 'g': { + unsigned long res; + struct group *groupinfo = getgrnam(optarg); + if (groupinfo) { + gid = groupinfo->gr_gid; + } else if (qemu_strtoul(optarg, NULL, 10, &res) == 0 && + (gid_t)res == res) { + gid = res; + } else { + error_report("invalid group '%s'", optarg); + exit(EXIT_FAILURE); + } + break; + } +#else + case 'u': + case 'g': + error_report("-%c not supported by this %s", ch, argv[0]); + exit(1); +#endif + case 'd': + daemonize = true; + break; + case 'q': + quiet = 1; + break; + case 'v': + ++loglevel; + break; + case 'T': + trace_opt_parse(optarg); + break; + case 'V': + version(argv[0]); + exit(EXIT_SUCCESS); + break; + case 'h': + usage(argv[0]); + exit(EXIT_SUCCESS); + break; + case '?': + error_report("Try `%s --help' for more information.", argv[0]); + exit(EXIT_FAILURE); + } + } + + /* set verbosity */ + noisy = !quiet && (loglevel >= 3); + verbose = quiet ? 0 : MIN(loglevel, 3); + + if (!trace_init_backends()) { + exit(EXIT_FAILURE); + } + trace_init_file(); + qemu_set_log(LOG_TRACE, &error_fatal); + + socket_activation = check_socket_activation(); + if (socket_activation == 0) { + SocketAddress saddr; + saddr = (SocketAddress){ + .type = SOCKET_ADDRESS_TYPE_UNIX, + .u.q_unix.path = socket_path, + }; + server_ioc = qio_channel_socket_new(); + if (qio_channel_socket_listen_sync(server_ioc, &saddr, + 1, &local_err) < 0) { + object_unref(OBJECT(server_ioc)); + error_report_err(local_err); + return 1; + } + } else { + /* Using socket activation - check user didn't use -p etc. */ + if (socket_path_specified) { + error_report("Unix socket can't be set when \ + using socket activation"); + exit(EXIT_FAILURE); + } + + /* Can only listen on a single socket. */ + if (socket_activation > 1) { + error_report("%s does not support socket activation \ + with LISTEN_FDS > 1", + argv[0]); + exit(EXIT_FAILURE); + } + server_ioc = qio_channel_socket_new_fd(FIRST_SOCKET_ACTIVATION_FD, + &local_err); + if (server_ioc == NULL) { + error_reportf_err(local_err, + "Failed to use socket activation: "); + exit(EXIT_FAILURE); + } + } + + qemu_init_main_loop(&error_fatal); + + server_watch = qio_channel_add_watch(QIO_CHANNEL(server_ioc), + G_IO_IN, + accept_client, + NULL, NULL); + + if (daemonize) { + if (daemon(0, 0) < 0) { + error_report("Failed to daemonize: %s", strerror(errno)); + exit(EXIT_FAILURE); + } + } + + if (daemonize || pidfile_specified) { + qemu_write_pidfile(pidfile, &error_fatal); + } + +#ifdef CONFIG_LIBCAP_NG + if (drop_privileges() < 0) { + error_report("Failed to drop privileges: %s", strerror(errno)); + exit(EXIT_FAILURE); + } +#endif + + state = RUNNING; + do { + main_loop_wait(false); + if (state == TERMINATE) { + state = TERMINATING; + close_server_socket(); + } + } while (num_active_sockets > 0); + + exit(EXIT_SUCCESS); +} diff --git a/tools/i386/rapl-msr-index.h b/tools/i386/rapl-msr-index.h new file mode 100644 index 000000000000..9a7118639ae3 --- /dev/null +++ b/tools/i386/rapl-msr-index.h @@ -0,0 +1,28 @@ +/* + * Allowed list of MSR for Privileged RAPL MSR helper commands for QEMU + * + * Copyright (C) 2023 Red Hat, Inc. <aharivel@redhat.com> + * + * Author: Anthony Harivel <aharivel@redhat.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; under version 2 of the License. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + */ + +/* + * Should stay in sync with the RAPL MSR + * in target/i386/cpu.h + */ +#define MSR_RAPL_POWER_UNIT 0x00000606 +#define MSR_PKG_POWER_LIMIT 0x00000610 +#define MSR_PKG_ENERGY_STATUS 0x00000611 +#define MSR_PKG_POWER_INFO 0x00000614
Introduce a privileged helper to access RAPL MSR. The privileged helper tool, qemu-vmsr-helper, is designed to provide virtual machines with the ability to read specific RAPL (Running Average Power Limit) MSRs without requiring CAP_SYS_RAWIO privileges or relying on external, out-of-tree patches. The helper tool leverages Unix permissions and SO_PEERCRED socket options to enforce access control, ensuring that only processes explicitly requesting read access via readmsr() from a valid Thread ID can access these MSRs. The list of RAPL MSRs that are allowed to be read by the helper tool is defined in rapl-msr-index.h. This list corresponds to the RAPL MSRs that will be supported in the next commit titled "Add support for RAPL MSRs in KVM/QEMU." Signed-off-by: Anthony Harivel <aharivel@redhat.com> --- docs/tools/index.rst | 1 + docs/tools/qemu-vmsr-helper.rst | 89 ++++++ meson.build | 5 + tools/i386/qemu-vmsr-helper.c | 507 ++++++++++++++++++++++++++++++++ tools/i386/rapl-msr-index.h | 28 ++ 5 files changed, 630 insertions(+) create mode 100644 docs/tools/qemu-vmsr-helper.rst create mode 100644 tools/i386/qemu-vmsr-helper.c create mode 100644 tools/i386/rapl-msr-index.h