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>

1 files changed, 32 insertions, 0 deletions

diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h
index 3f3d13f816..1d8fb1473b 100644
--- a/include/sysemu/kvm_int.h
+++ b/include/sysemu/kvm_int.h
@@ -14,6 +14,9 @@
 #include "qemu/accel.h"
 #include "qemu/queue.h"
 #include "sysemu/kvm.h"
+#include "hw/boards.h"
+#include "hw/i386/topology.h"
+#include "io/channel-socket.h"
 
 typedef struct KVMSlot
 {
@@ -50,6 +53,34 @@ typedef struct KVMMemoryListener {
 
 #define KVM_MSI_HASHTAB_SIZE    256
 
+typedef struct KVMHostTopoInfo {
+    /* Number of package on the Host */
+    unsigned int maxpkgs;
+    /* Number of cpus on the Host */
+    unsigned int maxcpus;
+    /* Number of cpus on each different package */
+    unsigned int *pkg_cpu_count;
+    /* Each package can have different maxticks */
+    unsigned int *maxticks;
+} KVMHostTopoInfo;
+
+struct KVMMsrEnergy {
+    pid_t pid;
+    bool enable;
+    char *socket_path;
+    QIOChannelSocket *sioc;
+    QemuThread msr_thr;
+    unsigned int guest_vcpus;
+    unsigned int guest_vsockets;
+    X86CPUTopoInfo guest_topo_info;
+    KVMHostTopoInfo host_topo;
+    const CPUArchIdList *guest_cpu_list;
+    uint64_t *msr_value;
+    uint64_t msr_unit;
+    uint64_t msr_limit;
+    uint64_t msr_info;
+};
+
 enum KVMDirtyRingReaperState {
     KVM_DIRTY_RING_REAPER_NONE = 0,
     /* The reaper is sleeping */
@@ -117,6 +148,7 @@ struct KVMState
     bool kvm_dirty_ring_with_bitmap;
     uint64_t kvm_eager_split_size;  /* Eager Page Splitting chunk size */
     struct KVMDirtyRingReaper reaper;
+    struct KVMMsrEnergy msr_energy;
     NotifyVmexitOption notify_vmexit;
     uint32_t notify_window;
     uint32_t xen_version;