Add support for RAPL MSRs in KVM/Qemu

Starting with the "Sandy Bridge" generation, Intel CPUs provide a RAPL
interface (Running Average Power Limit) for advertising the accumulated
energy consumption of various power domains (e.g. CPU packages, DRAM,
etc.).

The consumption is reported via MSRs (model specific registers) like
MSR_PKG_ENERGY_STATUS for the CPU package power domain. These MSRs are
64 bits registers that represent the accumulated energy consumption in
micro Joules. They are updated by microcode every ~1ms.

For now, KVM always returns 0 when the guest requests the value of
these MSRs. Use the KVM MSR filtering mechanism to allow QEMU handle
these MSRs dynamically in userspace.

To limit the amount of system calls for every MSR call, create a new
thread in QEMU that updates the "virtual" MSR values asynchronously.

Each vCPU has its own vMSR to reflect the independence of vCPUs. The
thread updates the vMSR values with the ratio of energy consumed of
the whole physical CPU package the vCPU thread runs on and the
thread's utime and stime values.

All other non-vCPU threads are also taken into account. Their energy
consumption is evenly distributed among all vCPUs threads running on
the same physical CPU package.

To overcome the problem that reading the RAPL MSR requires priviliged
access, a socket communication between QEMU and the qemu-vmsr-helper is
mandatory. You can specified the socket path in the parameter.

This feature is activated with -accel kvm,rapl=true,path=/path/sock.sock

Actual limitation:
- Works only on Intel host CPU because AMD CPUs are using different MSR
  adresses.

- Only the Package Power-Plane (MSR_PKG_ENERGY_STATUS) is reported at
  the moment.

Signed-off-by: Anthony Harivel <aharivel@redhat.com>
Link: https://lore.kernel.org/r/20240522153453.1230389-4-aharivel@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

5 files changed, 883 insertions, 1 deletions

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 1e121acef5..c6cc035df3 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -414,6 +414,10 @@ typedef enum X86Seg {
 #define MSR_IA32_TSX_CTRL		0x122
 #define MSR_IA32_TSCDEADLINE            0x6e0
 #define MSR_IA32_PKRS                   0x6e1
+#define MSR_RAPL_POWER_UNIT             0x00000606
+#define MSR_PKG_POWER_LIMIT             0x00000610
+#define MSR_PKG_ENERGY_STATUS           0x00000611
+#define MSR_PKG_POWER_INFO              0x00000614
 #define MSR_ARCH_LBR_CTL                0x000014ce
 #define MSR_ARCH_LBR_DEPTH              0x000014cf
 #define MSR_ARCH_LBR_FROM_0             0x00001500
@@ -1880,6 +1884,10 @@ typedef struct CPUArchState {
 
     uintptr_t retaddr;
 
+    /* RAPL MSR */
+    uint64_t msr_rapl_power_unit;
+    uint64_t msr_pkg_energy_status;
+
     /* Fields up to this point are cleared by a CPU reset */
     struct {} end_reset_fields;
 
diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
index becca2efa5..b4aab9a410 100644
--- a/target/i386/kvm/kvm.c
+++ b/target/i386/kvm/kvm.c
@@ -16,9 +16,12 @@
 #include "qapi/qapi-events-run-state.h"
 #include "qapi/error.h"
 #include "qapi/visitor.h"
+#include <math.h>
 #include <sys/ioctl.h>
 #include <sys/utsname.h>
 #include <sys/syscall.h>
+#include <sys/resource.h>
+#include <sys/time.h>
 
 #include <linux/kvm.h>
 #include <linux/kvm_para.h>
@@ -27,6 +30,7 @@
 
 #include "cpu.h"
 #include "host-cpu.h"
+#include "vmsr_energy.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/hw_accel.h"
 #include "sysemu/kvm_int.h"
@@ -2559,7 +2563,8 @@ static int kvm_get_supported_msrs(KVMState *s)
     return ret;
 }
 
-static bool kvm_rdmsr_core_thread_count(X86CPU *cpu, uint32_t msr,
+static bool kvm_rdmsr_core_thread_count(X86CPU *cpu,
+                                        uint32_t msr,
                                         uint64_t *val)
 {
     CPUState *cs = CPU(cpu);
@@ -2570,6 +2575,53 @@ static bool kvm_rdmsr_core_thread_count(X86CPU *cpu, uint32_t msr,
     return true;
 }
 
+static bool kvm_rdmsr_rapl_power_unit(X86CPU *cpu,
+                                      uint32_t msr,
+                                      uint64_t *val)
+{
+
+    CPUState *cs = CPU(cpu);
+
+    *val = cs->kvm_state->msr_energy.msr_unit;
+
+    return true;
+}
+
+static bool kvm_rdmsr_pkg_power_limit(X86CPU *cpu,
+                                      uint32_t msr,
+                                      uint64_t *val)
+{
+
+    CPUState *cs = CPU(cpu);
+
+    *val = cs->kvm_state->msr_energy.msr_limit;
+
+    return true;
+}
+
+static bool kvm_rdmsr_pkg_power_info(X86CPU *cpu,
+                                     uint32_t msr,
+                                     uint64_t *val)
+{
+
+    CPUState *cs = CPU(cpu);
+
+    *val = cs->kvm_state->msr_energy.msr_info;
+
+    return true;
+}
+
+static bool kvm_rdmsr_pkg_energy_status(X86CPU *cpu,
+                                        uint32_t msr,
+                                        uint64_t *val)
+{
+
+    CPUState *cs = CPU(cpu);
+    *val = cs->kvm_state->msr_energy.msr_value[cs->cpu_index];
+
+    return true;
+}
+
 static Notifier smram_machine_done;
 static KVMMemoryListener smram_listener;
 static AddressSpace smram_address_space;
@@ -2604,6 +2656,340 @@ static void register_smram_listener(Notifier *n, void *unused)
                                  &smram_address_space, 1, "kvm-smram");
 }
 
+static void *kvm_msr_energy_thread(void *data)
+{
+    KVMState *s = data;
+    struct KVMMsrEnergy *vmsr = &s->msr_energy;
+
+    g_autofree vmsr_package_energy_stat *pkg_stat = NULL;
+    g_autofree vmsr_thread_stat *thd_stat = NULL;
+    g_autofree CPUState *cpu = NULL;
+    g_autofree unsigned int *vpkgs_energy_stat = NULL;
+    unsigned int num_threads = 0;
+
+    X86CPUTopoIDs topo_ids;
+
+    rcu_register_thread();
+
+    /* Allocate memory for each package energy status */
+    pkg_stat = g_new0(vmsr_package_energy_stat, vmsr->host_topo.maxpkgs);
+
+    /* Allocate memory for thread stats */
+    thd_stat = g_new0(vmsr_thread_stat, 1);
+
+    /* Allocate memory for holding virtual package energy counter */
+    vpkgs_energy_stat = g_new0(unsigned int, vmsr->guest_vsockets);
+
+    /* Populate the max tick of each packages */
+    for (int i = 0; i < vmsr->host_topo.maxpkgs; i++) {
+        /*
+         * Max numbers of ticks per package
+         * Time in second * Number of ticks/second * Number of cores/package
+         * ex: 100 ticks/second/CPU, 12 CPUs per Package gives 1200 ticks max
+         */
+        vmsr->host_topo.maxticks[i] = (MSR_ENERGY_THREAD_SLEEP_US / 1000000)
+                        * sysconf(_SC_CLK_TCK)
+                        * vmsr->host_topo.pkg_cpu_count[i];
+    }
+
+    while (true) {
+        /* Get all qemu threads id */
+        g_autofree pid_t *thread_ids =
+            thread_ids = vmsr_get_thread_ids(vmsr->pid, &num_threads);
+
+        if (thread_ids == NULL) {
+            goto clean;
+        }
+
+        thd_stat = g_renew(vmsr_thread_stat, thd_stat, num_threads);
+        /* Unlike g_new0, g_renew0 function doesn't exist yet... */
+        memset(thd_stat, 0, num_threads * sizeof(vmsr_thread_stat));
+
+        /* Populate all the thread stats */
+        for (int i = 0; i < num_threads; i++) {
+            thd_stat[i].utime = g_new0(unsigned long long, 2);
+            thd_stat[i].stime = g_new0(unsigned long long, 2);
+            thd_stat[i].thread_id = thread_ids[i];
+            vmsr_read_thread_stat(vmsr->pid,
+                                  thd_stat[i].thread_id,
+                                  thd_stat[i].utime,
+                                  thd_stat[i].stime,
+                                  &thd_stat[i].cpu_id);
+            thd_stat[i].pkg_id =
+                vmsr_get_physical_package_id(thd_stat[i].cpu_id);
+        }
+
+        /* Retrieve all packages power plane energy counter */
+        for (int i = 0; i < vmsr->host_topo.maxpkgs; i++) {
+            for (int j = 0; j < num_threads; j++) {
+                /*
+                 * Use the first thread we found that ran on the CPU
+                 * of the package to read the packages energy counter
+                 */
+                if (thd_stat[j].pkg_id == i) {
+                    pkg_stat[i].e_start =
+                    vmsr_read_msr(MSR_PKG_ENERGY_STATUS,
+                                  thd_stat[j].cpu_id,
+                                  thd_stat[j].thread_id,
+                                  s->msr_energy.sioc);
+                    break;
+                }
+            }
+        }
+
+        /* Sleep a short period while the other threads are working */
+        usleep(MSR_ENERGY_THREAD_SLEEP_US);
+
+        /*
+         * Retrieve all packages power plane energy counter
+         * Calculate the delta of all packages
+         */
+        for (int i = 0; i < vmsr->host_topo.maxpkgs; i++) {
+            for (int j = 0; j < num_threads; j++) {
+                /*
+                 * Use the first thread we found that ran on the CPU
+                 * of the package to read the packages energy counter
+                 */
+                if (thd_stat[j].pkg_id == i) {
+                    pkg_stat[i].e_end =
+                    vmsr_read_msr(MSR_PKG_ENERGY_STATUS,
+                                  thd_stat[j].cpu_id,
+                                  thd_stat[j].thread_id,
+                                  s->msr_energy.sioc);
+                    /*
+                     * Prevent the case we have migrate the VM
+                     * during the sleep period or any other cases
+                     * were energy counter might be lower after
+                     * the sleep period.
+                     */
+                    if (pkg_stat[i].e_end > pkg_stat[i].e_start) {
+                        pkg_stat[i].e_delta =
+                            pkg_stat[i].e_end - pkg_stat[i].e_start;
+                    } else {
+                        pkg_stat[i].e_delta = 0;
+                    }
+                    break;
+                }
+            }
+        }
+
+        /* Delta of ticks spend by each thread between the sample */
+        for (int i = 0; i < num_threads; i++) {
+            vmsr_read_thread_stat(vmsr->pid,
+                                  thd_stat[i].thread_id,
+                                  thd_stat[i].utime,
+                                  thd_stat[i].stime,
+                                  &thd_stat[i].cpu_id);
+
+            if (vmsr->pid < 0) {
+                /*
+                 * We don't count the dead thread
+                 * i.e threads that existed before the sleep
+                 * and not anymore
+                 */
+                thd_stat[i].delta_ticks = 0;
+            } else {
+                vmsr_delta_ticks(thd_stat, i);
+            }
+        }
+
+        /*
+         * Identify the vcpu threads
+         * Calculate the number of vcpu per package
+         */
+        CPU_FOREACH(cpu) {
+            for (int i = 0; i < num_threads; i++) {
+                if (cpu->thread_id == thd_stat[i].thread_id) {
+                    thd_stat[i].is_vcpu = true;
+                    thd_stat[i].vcpu_id = cpu->cpu_index;
+                    pkg_stat[thd_stat[i].pkg_id].nb_vcpu++;
+                    thd_stat[i].acpi_id = kvm_arch_vcpu_id(cpu);
+                    break;
+                }
+            }
+        }
+
+        /* Retrieve the virtual package number of each vCPU */
+        for (int i = 0; i < vmsr->guest_cpu_list->len; i++) {
+            for (int j = 0; j < num_threads; j++) {
+                if ((thd_stat[j].acpi_id ==
+                        vmsr->guest_cpu_list->cpus[i].arch_id)
+                    && (thd_stat[j].is_vcpu == true)) {
+                    x86_topo_ids_from_apicid(thd_stat[j].acpi_id,
+                        &vmsr->guest_topo_info, &topo_ids);
+                    thd_stat[j].vpkg_id = topo_ids.pkg_id;
+                }
+            }
+        }
+
+        /* Calculate the total energy of all non-vCPU thread */
+        for (int i = 0; i < num_threads; i++) {
+            if ((thd_stat[i].is_vcpu != true) &&
+                (thd_stat[i].delta_ticks > 0)) {
+                double temp;
+                temp = vmsr_get_ratio(pkg_stat[thd_stat[i].pkg_id].e_delta,
+                    thd_stat[i].delta_ticks,
+                    vmsr->host_topo.maxticks[thd_stat[i].pkg_id]);
+                pkg_stat[thd_stat[i].pkg_id].e_ratio
+                    += (uint64_t)lround(temp);
+            }
+        }
+
+        /* Calculate the ratio per non-vCPU thread of each package */
+        for (int i = 0; i < vmsr->host_topo.maxpkgs; i++) {
+            if (pkg_stat[i].nb_vcpu > 0) {
+                pkg_stat[i].e_ratio = pkg_stat[i].e_ratio / pkg_stat[i].nb_vcpu;
+            }
+        }
+
+        /*
+         * Calculate the energy for each Package:
+         * Energy Package = sum of each vCPU energy that belongs to the package
+         */
+        for (int i = 0; i < num_threads; i++) {
+            if ((thd_stat[i].is_vcpu == true) && \
+                    (thd_stat[i].delta_ticks > 0)) {
+                double temp;
+                temp = vmsr_get_ratio(pkg_stat[thd_stat[i].pkg_id].e_delta,
+                    thd_stat[i].delta_ticks,
+                    vmsr->host_topo.maxticks[thd_stat[i].pkg_id]);
+                vpkgs_energy_stat[thd_stat[i].vpkg_id] +=
+                    (uint64_t)lround(temp);
+                vpkgs_energy_stat[thd_stat[i].vpkg_id] +=
+                    pkg_stat[thd_stat[i].pkg_id].e_ratio;
+            }
+        }
+
+        /*
+         * Finally populate the vmsr register of each vCPU with the total
+         * package value to emulate the real hardware where each CPU return the
+         * value of the package it belongs.
+         */
+        for (int i = 0; i < num_threads; i++) {
+            if ((thd_stat[i].is_vcpu == true) && \
+                    (thd_stat[i].delta_ticks > 0)) {
+                vmsr->msr_value[thd_stat[i].vcpu_id] = \
+                                        vpkgs_energy_stat[thd_stat[i].vpkg_id];
+          }
+        }
+
+        /* Freeing memory before zeroing the pointer */
+        for (int i = 0; i < num_threads; i++) {
+            g_free(thd_stat[i].utime);
+            g_free(thd_stat[i].stime);
+        }
+   }
+
+clean:
+    rcu_unregister_thread();
+    return NULL;
+}
+
+static int kvm_msr_energy_thread_init(KVMState *s, MachineState *ms)
+{
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
+    struct KVMMsrEnergy *r = &s->msr_energy;
+    int ret = 0;
+
+    /*
+     * Sanity check
+     * 1. Host cpu must be Intel cpu
+     * 2. RAPL must be enabled on the Host
+     */
+    if (is_host_cpu_intel()) {
+        error_report("The RAPL feature can only be enabled on hosts\
+                      with Intel CPU models");
+        ret = 1;
+        goto out;
+    }
+
+    if (!is_rapl_enabled()) {
+        ret = 1;
+        goto out;
+    }
+
+    /* Retrieve the virtual topology */
+    vmsr_init_topo_info(&r->guest_topo_info, ms);
+
+    /* Retrieve the number of vcpu */
+    r->guest_vcpus = ms->smp.cpus;
+
+    /* Retrieve the number of virtual sockets */
+    r->guest_vsockets = ms->smp.sockets;
+
+    /* Allocate register memory (MSR_PKG_STATUS) for each vcpu */
+    r->msr_value = g_new0(uint64_t, r->guest_vcpus);
+
+    /* Retrieve the CPUArchIDlist */
+    r->guest_cpu_list = mc->possible_cpu_arch_ids(ms);
+
+    /* Max number of cpus on the Host */
+    r->host_topo.maxcpus = vmsr_get_maxcpus();
+    if (r->host_topo.maxcpus == 0) {
+        error_report("host max cpus = 0");
+        ret = 1;
+        goto out;
+    }
+
+    /* Max number of packages on the host */
+    r->host_topo.maxpkgs = vmsr_get_max_physical_package(r->host_topo.maxcpus);
+    if (r->host_topo.maxpkgs == 0) {
+        error_report("host max pkgs = 0");
+        ret = 1;
+        goto out;
+    }
+
+    /* Allocate memory for each package on the host */
+    r->host_topo.pkg_cpu_count = g_new0(unsigned int, r->host_topo.maxpkgs);
+    r->host_topo.maxticks = g_new0(unsigned int, r->host_topo.maxpkgs);
+
+    vmsr_count_cpus_per_package(r->host_topo.pkg_cpu_count,
+                                r->host_topo.maxpkgs);
+    for (int i = 0; i < r->host_topo.maxpkgs; i++) {
+        if (r->host_topo.pkg_cpu_count[i] == 0) {
+            error_report("cpu per packages = 0 on package_%d", i);
+            ret = 1;
+            goto out;
+        }
+    }
+
+    /* Get QEMU PID*/
+    r->pid = getpid();
+
+    /* Compute the socket path if necessary */
+    if (s->msr_energy.socket_path == NULL) {
+        s->msr_energy.socket_path = vmsr_compute_default_paths();
+    }
+
+    /* Open socket with vmsr helper */
+    s->msr_energy.sioc = vmsr_open_socket(s->msr_energy.socket_path);
+
+    if (s->msr_energy.sioc == NULL) {
+        error_report("vmsr socket opening failed");
+        ret = 1;
+        goto out;
+    }
+
+    /* Those MSR values should not change */
+    r->msr_unit  = vmsr_read_msr(MSR_RAPL_POWER_UNIT, 0, r->pid,
+                                    s->msr_energy.sioc);
+    r->msr_limit = vmsr_read_msr(MSR_PKG_POWER_LIMIT, 0, r->pid,
+                                    s->msr_energy.sioc);
+    r->msr_info  = vmsr_read_msr(MSR_PKG_POWER_INFO, 0, r->pid,
+                                    s->msr_energy.sioc);
+    if (r->msr_unit == 0 || r->msr_limit == 0 || r->msr_info == 0) {
+        error_report("can't read any virtual msr");
+        ret = 1;
+        goto out;
+    }
+
+    qemu_thread_create(&r->msr_thr, "kvm-msr",
+                       kvm_msr_energy_thread,
+                       s, QEMU_THREAD_JOINABLE);
+out:
+    return ret;
+}
+
 int kvm_arch_get_default_type(MachineState *ms)
 {
     return 0;
@@ -2804,6 +3190,49 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
                          strerror(-ret));
             exit(1);
         }
+
+        if (s->msr_energy.enable == true) {
+            r = kvm_filter_msr(s, MSR_RAPL_POWER_UNIT,
+                               kvm_rdmsr_rapl_power_unit, NULL);
+            if (!r) {
+                error_report("Could not install MSR_RAPL_POWER_UNIT \
+                                handler: %s",
+                             strerror(-ret));
+                exit(1);
+            }
+
+            r = kvm_filter_msr(s, MSR_PKG_POWER_LIMIT,
+                               kvm_rdmsr_pkg_power_limit, NULL);
+            if (!r) {
+                error_report("Could not install MSR_PKG_POWER_LIMIT \
+                                handler: %s",
+                             strerror(-ret));
+                exit(1);
+            }
+
+            r = kvm_filter_msr(s, MSR_PKG_POWER_INFO,
+                               kvm_rdmsr_pkg_power_info, NULL);
+            if (!r) {
+                error_report("Could not install MSR_PKG_POWER_INFO \
+                                handler: %s",
+                             strerror(-ret));
+                exit(1);
+            }
+            r = kvm_filter_msr(s, MSR_PKG_ENERGY_STATUS,
+                               kvm_rdmsr_pkg_energy_status, NULL);
+            if (!r) {
+                error_report("Could not install MSR_PKG_ENERGY_STATUS \
+                                handler: %s",
+                             strerror(-ret));
+                exit(1);
+            }
+            r = kvm_msr_energy_thread_init(s, ms);
+            if (r) {
+                error_report("kvm : error RAPL feature requirement not meet");
+                exit(1);
+            }
+
+        }
     }
 
     return 0;
diff --git a/target/i386/kvm/meson.build b/target/i386/kvm/meson.build
index e7850981e6..3996cafaf2 100644
--- a/target/i386/kvm/meson.build
+++ b/target/i386/kvm/meson.build
@@ -3,6 +3,7 @@ i386_kvm_ss = ss.source_set()
 i386_kvm_ss.add(files(
   'kvm.c',
   'kvm-cpu.c',
+  'vmsr_energy.c',
 ))
 
 i386_kvm_ss.add(when: 'CONFIG_XEN_EMU', if_true: files('xen-emu.c'))
diff --git a/target/i386/kvm/vmsr_energy.c b/target/i386/kvm/vmsr_energy.c
new file mode 100644
index 0000000000..a1d78f2f2a
--- /dev/null
+++ b/target/i386/kvm/vmsr_energy.c
@@ -0,0 +1,345 @@
+/*
+ * QEMU KVM support -- x86 virtual RAPL msr
+ *
+ * Copyright 2024 Red Hat, Inc. 2024
+ *
+ *  Author:
+ *      Anthony Harivel <aharivel@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/error-report.h"
+#include "vmsr_energy.h"
+#include "io/channel.h"
+#include "io/channel-socket.h"
+#include "hw/boards.h"
+#include "cpu.h"
+#include "host-cpu.h"
+
+char *vmsr_compute_default_paths(void)
+{
+    g_autofree char *state = qemu_get_local_state_dir();
+
+    return g_build_filename(state, "run", "qemu-vmsr-helper.sock", NULL);
+}
+
+bool is_host_cpu_intel(void)
+{
+    int family, model, stepping;
+    char vendor[CPUID_VENDOR_SZ + 1];
+
+    host_cpu_vendor_fms(vendor, &family, &model, &stepping);
+
+    return strcmp(vendor, CPUID_VENDOR_INTEL);
+}
+
+int is_rapl_enabled(void)
+{
+    const char *path = "/sys/class/powercap/intel-rapl/enabled";
+    FILE *file = fopen(path, "r");
+    int value = 0;
+
+    if (file != NULL) {
+        if (fscanf(file, "%d", &value) != 1) {
+            error_report("INTEL RAPL not enabled");
+        }
+        fclose(file);
+    } else {
+        error_report("Error opening %s", path);
+    }
+
+    return value;
+}
+
+QIOChannelSocket *vmsr_open_socket(const char *path)
+{
+    g_autofree char *socket_path = NULL;
+
+    socket_path = g_strdup(path);
+
+    SocketAddress saddr = {
+        .type = SOCKET_ADDRESS_TYPE_UNIX,
+        .u.q_unix.path = socket_path
+    };
+
+    QIOChannelSocket *sioc = qio_channel_socket_new();
+    Error *local_err = NULL;
+
+    qio_channel_set_name(QIO_CHANNEL(sioc), "vmsr-helper");
+    qio_channel_socket_connect_sync(sioc,
+                                    &saddr,
+                                    &local_err);
+    if (local_err) {
+        /* Close socket. */
+        qio_channel_close(QIO_CHANNEL(sioc), NULL);
+        object_unref(OBJECT(sioc));
+        sioc = NULL;
+        goto out;
+    }
+
+    qio_channel_set_delay(QIO_CHANNEL(sioc), false);
+out:
+    return sioc;
+}
+
+uint64_t vmsr_read_msr(uint32_t reg, uint32_t cpu_id, uint32_t tid,
+                       QIOChannelSocket *sioc)
+{
+    uint64_t data = 0;
+    int r = 0;
+    Error *local_err = NULL;
+    uint32_t buffer[3];
+    /*
+     * Send the required arguments:
+     * 1. RAPL MSR register to read
+     * 2. On which CPU ID
+     * 3. From which vCPU (Thread ID)
+     */
+    buffer[0] = reg;
+    buffer[1] = cpu_id;
+    buffer[2] = tid;
+
+    r = qio_channel_write_all(QIO_CHANNEL(sioc),
+                              (char *)buffer, sizeof(buffer),
+                              &local_err);
+    if (r < 0) {
+        goto out_close;
+    }
+
+    r = qio_channel_read(QIO_CHANNEL(sioc),
+                             (char *)&data, sizeof(data),
+                             &local_err);
+    if (r < 0) {
+        data = 0;
+        goto out_close;
+    }
+
+out_close:
+   return data;
+}
+
+/* Retrieve the max number of physical package */
+unsigned int vmsr_get_max_physical_package(unsigned int max_cpus)
+{
+    const char *dir = "/sys/devices/system/cpu/";
+    const char *topo_path = "topology/physical_package_id";
+    g_autofree int *uniquePackages = g_new0(int, max_cpus);
+    unsigned int packageCount = 0;
+    FILE *file = NULL;
+
+    for (int i = 0; i < max_cpus; i++) {
+        g_autofree char *filePath = NULL;
+        g_autofree char *cpuid = g_strdup_printf("cpu%d", i);
+
+        filePath = g_build_filename(dir, cpuid, topo_path, NULL);
+
+        file = fopen(filePath, "r");
+
+        if (file == NULL) {
+            error_report("Error opening physical_package_id file");
+            return 0;
+        }
+
+        char packageId[10];
+        if (fgets(packageId, sizeof(packageId), file) == NULL) {
+            packageCount = 0;
+        }
+
+        fclose(file);
+
+        int currentPackageId = atoi(packageId);
+
+        bool isUnique = true;
+        for (int j = 0; j < packageCount; j++) {
+            if (uniquePackages[j] == currentPackageId) {
+                isUnique = false;
+                break;
+            }
+        }
+
+        if (isUnique) {
+            uniquePackages[packageCount] = currentPackageId;
+            packageCount++;
+
+            if (packageCount >= max_cpus) {
+                break;
+            }
+        }
+    }
+
+    return (packageCount == 0) ? 1 : packageCount;
+}
+
+/* Retrieve the max number of physical cpu on the host */
+unsigned int vmsr_get_maxcpus(void)
+{
+    GDir *dir;
+    const gchar *entry_name;
+    unsigned int cpu_count = 0;
+    const char *path = "/sys/devices/system/cpu/";
+
+    dir = g_dir_open(path, 0, NULL);
+    if (dir == NULL) {
+        error_report("Unable to open cpu directory");
+        return -1;
+    }
+
+    while ((entry_name = g_dir_read_name(dir)) != NULL) {
+        if (g_ascii_strncasecmp(entry_name, "cpu", 3) == 0 &&
+            isdigit(entry_name[3])) {
+            cpu_count++;
+        }
+    }
+
+    g_dir_close(dir);
+
+    return cpu_count;
+}
+
+/* Count the number of physical cpu on each packages */
+unsigned int vmsr_count_cpus_per_package(unsigned int *package_count,
+                                         unsigned int max_pkgs)
+{
+    g_autofree char *file_contents = NULL;
+    g_autofree char *path = NULL;
+    g_autofree char *path_name = NULL;
+    gsize length;
+
+    /* Iterate over cpus and count cpus in each package */
+    for (int cpu_id = 0; ; cpu_id++) {
+        path_name = g_strdup_printf("/sys/devices/system/cpu/cpu%d/"
+            "topology/physical_package_id", cpu_id);
+
+        path = g_build_filename(path_name, NULL);
+
+        if (!g_file_get_contents(path, &file_contents, &length, NULL)) {
+            break; /* No more cpus */
+        }
+
+        /* Get the physical package ID for this CPU */
+        int package_id = atoi(file_contents);
+
+        /* Check if the package ID is within the known number of packages */
+        if (package_id >= 0 && package_id < max_pkgs) {
+            /* If yes, count the cpu for this package*/
+            package_count[package_id]++;
+        }
+    }
+
+    return 0;
+}
+
+/* Get the physical package id from a given cpu id */
+int vmsr_get_physical_package_id(int cpu_id)
+{
+    g_autofree char *file_contents = NULL;
+    g_autofree char *file_path = NULL;
+    int package_id = -1;
+    gsize length;
+
+    file_path = g_strdup_printf("/sys/devices/system/cpu/cpu%d"
+        "/topology/physical_package_id", cpu_id);
+
+    if (!g_file_get_contents(file_path, &file_contents, &length, NULL)) {
+        goto out;
+    }
+
+    package_id = atoi(file_contents);
+
+out:
+    return package_id;
+}
+
+/* Read the scheduled time for a given thread of a give pid */
+void vmsr_read_thread_stat(pid_t pid,
+                      unsigned int thread_id,
+                      unsigned long long *utime,
+                      unsigned long long *stime,
+                      unsigned int *cpu_id)
+{
+    g_autofree char *path = NULL;
+    g_autofree char *path_name = NULL;
+
+    path_name = g_strdup_printf("/proc/%u/task/%d/stat", pid, thread_id);
+
+    path = g_build_filename(path_name, NULL);
+
+    FILE *file = fopen(path, "r");
+    if (file == NULL) {
+        pid = -1;
+        return;
+    }
+
+    if (fscanf(file, "%*d (%*[^)]) %*c %*d %*d %*d %*d %*d %*u %*u %*u %*u %*u"
+        " %llu %llu %*d %*d %*d %*d %*d %*d %*u %*u %*d %*u %*u"
+        " %*u %*u %*u %*u %*u %*u %*u %*u %*u %*d %*u %*u %u",
+           utime, stime, cpu_id) != 3)
+    {
+        pid = -1;
+        return;
+    }
+
+    fclose(file);
+    return;
+}
+
+/* Read QEMU stat task folder to retrieve all QEMU threads ID */
+pid_t *vmsr_get_thread_ids(pid_t pid, unsigned int *num_threads)
+{
+    g_autofree char *task_path = g_strdup_printf("%d/task", pid);
+    g_autofree char *path = g_build_filename("/proc", task_path, NULL);
+
+    DIR *dir = opendir(path);
+    if (dir == NULL) {
+        error_report("Error opening /proc/qemu/task");
+        return NULL;
+    }
+
+    pid_t *thread_ids = NULL;
+    unsigned int thread_count = 0;
+
+    g_autofree struct dirent *ent = NULL;
+    while ((ent = readdir(dir)) != NULL) {
+        if (ent->d_name[0] == '.') {
+            continue;
+        }
+        pid_t tid = atoi(ent->d_name);
+        if (pid != tid) {
+            thread_ids = g_renew(pid_t, thread_ids, (thread_count + 1));
+            thread_ids[thread_count] = tid;
+            thread_count++;
+        }
+    }
+
+    closedir(dir);
+
+    *num_threads = thread_count;
+    return thread_ids;
+}
+
+void vmsr_delta_ticks(vmsr_thread_stat *thd_stat, int i)
+{
+    thd_stat[i].delta_ticks = (thd_stat[i].utime[1] + thd_stat[i].stime[1])
+                            - (thd_stat[i].utime[0] + thd_stat[i].stime[0]);
+}
+
+double vmsr_get_ratio(uint64_t e_delta,
+                      unsigned long long delta_ticks,
+                      unsigned int maxticks)
+{
+    return (e_delta / 100.0) * ((100.0 / maxticks) * delta_ticks);
+}
+
+void vmsr_init_topo_info(X86CPUTopoInfo *topo_info,
+                           const MachineState *ms)
+{
+    topo_info->dies_per_pkg = ms->smp.dies;
+    topo_info->modules_per_die = ms->smp.modules;
+    topo_info->cores_per_module = ms->smp.cores;
+    topo_info->threads_per_core = ms->smp.threads;
+}
+
diff --git a/target/i386/kvm/vmsr_energy.h b/target/i386/kvm/vmsr_energy.h
new file mode 100644
index 0000000000..16cc1f4814
--- /dev/null
+++ b/target/i386/kvm/vmsr_energy.h
@@ -0,0 +1,99 @@
+/*
+ * QEMU KVM support -- x86 virtual energy-related MSR.
+ *
+ * Copyright 2024 Red Hat, Inc. 2024
+ *
+ *  Author:
+ *      Anthony Harivel <aharivel@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef VMSR_ENERGY_H
+#define VMSR_ENERGY_H
+
+#include <stdint.h>
+#include "qemu/osdep.h"
+#include "io/channel-socket.h"
+#include "hw/i386/topology.h"
+
+/*
+ * Define the interval time in micro seconds between 2 samples of
+ * energy related MSRs
+ */
+#define MSR_ENERGY_THREAD_SLEEP_US 1000000.0
+
+/*
+ * Thread statistic
+ * @ thread_id: TID (thread ID)
+ * @ is_vcpu: true if TID is vCPU thread
+ * @ cpu_id: CPU number last executed on
+ * @ pkg_id: package number of the CPU
+ * @ vcpu_id: vCPU ID
+ * @ vpkg: virtual package number
+ * @ acpi_id: APIC id of the vCPU
+ * @ utime: amount of clock ticks the thread
+ *          has been scheduled in User mode
+ * @ stime: amount of clock ticks the thread
+ *          has been scheduled in System mode
+ * @ delta_ticks: delta of utime+stime between
+ *          the two samples (before/after sleep)
+ */
+struct vmsr_thread_stat {
+    unsigned int thread_id;
+    bool is_vcpu;
+    unsigned int cpu_id;
+    unsigned int pkg_id;
+    unsigned int vpkg_id;
+    unsigned int vcpu_id;
+    unsigned long acpi_id;
+    unsigned long long *utime;
+    unsigned long long *stime;
+    unsigned long long delta_ticks;
+};
+
+/*
+ * Package statistic
+ * @ e_start: package energy counter before the sleep
+ * @ e_end: package energy counter after the sleep
+ * @ e_delta: delta of package energy counter
+ * @ e_ratio: store the energy ratio of non-vCPU thread
+ * @ nb_vcpu: number of vCPU running on this package
+ */
+struct vmsr_package_energy_stat {
+    uint64_t e_start;
+    uint64_t e_end;
+    uint64_t e_delta;
+    uint64_t e_ratio;
+    unsigned int nb_vcpu;
+};
+
+typedef struct vmsr_thread_stat vmsr_thread_stat;
+typedef struct vmsr_package_energy_stat vmsr_package_energy_stat;
+
+char *vmsr_compute_default_paths(void);
+void vmsr_read_thread_stat(pid_t pid,
+                      unsigned int thread_id,
+                      unsigned long long *utime,
+                      unsigned long long *stime,
+                      unsigned int *cpu_id);
+
+QIOChannelSocket *vmsr_open_socket(const char *path);
+uint64_t vmsr_read_msr(uint32_t reg, uint32_t cpu_id,
+                       uint32_t tid, QIOChannelSocket *sioc);
+void vmsr_delta_ticks(vmsr_thread_stat *thd_stat, int i);
+unsigned int vmsr_get_maxcpus(void);
+unsigned int vmsr_get_max_physical_package(unsigned int max_cpus);
+unsigned int vmsr_count_cpus_per_package(unsigned int *package_count,
+                                         unsigned int max_pkgs);
+int vmsr_get_physical_package_id(int cpu_id);
+pid_t *vmsr_get_thread_ids(pid_t pid, unsigned int *num_threads);
+double vmsr_get_ratio(uint64_t e_delta,
+                      unsigned long long delta_ticks,
+                      unsigned int maxticks);
+void vmsr_init_topo_info(X86CPUTopoInfo *topo_info, const MachineState *ms);
+bool is_host_cpu_intel(void);
+int is_rapl_enabled(void);
+#endif /* VMSR_ENERGY_H */