Hi Daniel,
Daniel P. Berrangé, Apr 18, 2024 at 18:42:
> On Thu, Apr 11, 2024 at 02:14:34PM +0200, Anthony Harivel wrote:
> > 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 <ahari...@redhat.com>
> > ---
> > accel/kvm/kvm-all.c | 27 +++
> > docs/specs/index.rst | 1 +
> > docs/specs/rapl-msr.rst | 155 ++++++++++++
> > include/sysemu/kvm.h | 2 +
> > include/sysemu/kvm_int.h | 32 +++
> > target/i386/cpu.h | 8 +
> > target/i386/kvm/kvm-cpu.c | 9 +
> > target/i386/kvm/kvm.c | 428 ++++++++++++++++++++++++++++++++++
> > target/i386/kvm/meson.build | 1 +
> > target/i386/kvm/vmsr_energy.c | 335 ++++++++++++++++++++++++++
> > target/i386/kvm/vmsr_energy.h | 99 ++++++++
> > 11 files changed, 1097 insertions(+)
> > create mode 100644 docs/specs/rapl-msr.rst
> > create mode 100644 target/i386/kvm/vmsr_energy.c
> > create mode 100644 target/i386/kvm/vmsr_energy.h
> >
>
> > diff --git a/target/i386/kvm/kvm-cpu.c b/target/i386/kvm/kvm-cpu.c
> > index 9c791b7b0520..eafb625839b8 100644
> > --- a/target/i386/kvm/kvm-cpu.c
> > +++ b/target/i386/kvm/kvm-cpu.c
> > @@ -50,6 +50,15 @@ static bool kvm_cpu_realizefn(CPUState *cs, Error **errp)
> > MSR_IA32_UCODE_REV);
> > }
> > }
> > +
> > + if (kvm_is_rapl_feat_enable(cs)) {
> > + if (!IS_INTEL_CPU(env)) {
> > + error_setg(errp, "RAPL feature can only be\
> > + enabled with Intel CPU models");
> > + return false;
> > + }
> > + }
>
> I see a crash in kvm_is_rapl_feat_enable() from this caller,
> when I run with this kind of command line:
>
> $ qemu-system-x86_64 \
> -kernel /lib/modules/6.6.9-100.fc38.x86_64/vmlinuz \
> -initrd tiny-initrd.img -m 2000 -serial stdio -nodefaults \
> -display none -accel kvm -append "console=ttyS0 quiet"
>
>
> #0 0x0000555555bc14b7 in kvm_is_rapl_feat_enable
> (cs=cs@entry=0x555557b83470) at ../target/i386/kvm/kvm.c:2531
> #1 0x0000555555bc7534 in kvm_cpu_realizefn (cs=0x555557b83470,
> errp=0x7fffffffd2a0) at ../target/i386/kvm/kvm-cpu.c:54
> #2 0x0000555555d2432a in accel_cpu_common_realize (cpu=0x555557b83470,
> errp=0x7fffffffd2a0) at ../accel/accel-target.c:130
> #3 0x0000555555cdd955 in cpu_exec_realizefn (cpu=cpu@entry=0x555557b83470,
> errp=errp@entry=0x7fffffffd2a0) at ../cpu-target.c:137
> #4 0x0000555555c14b89 in x86_cpu_realizefn (dev=0x555557b83470,
> errp=0x7fffffffd310) at ../target/i386/cpu.c:7320
> #5 0x0000555555d58f4b in device_set_realized (obj=<optimized out>,
> value=<optimized out>, errp=0x7fffffffd390) at ../hw/core/qdev.c:510
> #6 0x0000555555d5d78d in property_set_bool (obj=0x555557b83470, v=<optimized
> out>, name=<optimized out>, opaque=0x5555578558e0, errp=0x7fffffffd390)
> at ../qom/object.c:2358
> #7 0x0000555555d60b0b in object_property_set (obj=obj@entry=0x555557b83470,
> name=name@entry=0x55555607c799 "realized", v=v@entry=0x555557b8ccb0,
> errp=0x7fffffffd390,
> errp@entry=0x555556e210d8 <error_fatal>) at ../qom/object.c:1472
> #8 0x0000555555d6444f in object_property_set_qobject
> (obj=obj@entry=0x555557b83470, name=name@entry=0x55555607c799 "realized",
> value=value@entry=0x555557854800, errp=errp@entry=0x555556e210d8
> <error_fatal>)
> at ../qom/qom-qobject.c:28
> #9 0x0000555555d61174 in object_property_set_bool
> (obj=0x555557b83470, name=name@entry=0x55555607c799 "realized",
> value=value@entry=true, errp=errp@entry=0x555556e210d8 <error_fatal>) at
> ../qom/object.c:1541
> #10 0x0000555555d59a3c in qdev_realize (dev=<optimized out>,
> bus=bus@entry=0x0, errp=errp@entry=0x555556e210d8 <error_fatal>) at
> ../hw/core/qdev.c:292
> #11 0x0000555555bd51e0 in x86_cpu_new (x86ms=<optimized out>, apic_id=0,
> errp=0x555556e210d8 <error_fatal>) at ../hw/i386/x86.c:105
> #12 0x0000555555bd52ce in x86_cpus_init (x86ms=x86ms@entry=0x555557aaed30,
> default_cpu_version=<optimized out>) at ../hw/i386/x86.c:156
> #13 0x0000555555bdc1a7 in pc_init1 (machine=0x555557aaed30,
> pci_type=0x55555604aa61 "i440FX") at ../hw/i386/pc_piix.c:185
> #14 0x0000555555947a11 in machine_run_board_init (machine=0x555557aaed30,
> mem_path=<optimized out>, errp=<optimized out>, errp@entry=0x555556e210d8
> <error_fatal>)
> at ../hw/core/machine.c:1547
> #15 0x0000555555b020ed in qemu_init_board () at ../system/vl.c:2613
> #16 qmp_x_exit_preconfig (errp=0x555556e210d8 <error_fatal>) at
> ../system/vl.c:2705
> #17 0x0000555555b0611e in qemu_init (argc=<optimized out>, argv=<optimized
> out>) at ../system/vl.c:3739
> #18 0x0000555555897ca9 in main (argc=<optimized out>, argv=<optimized out>)
> at ../system/main.c:47
>
> The problem is that 'cs->kvm_state' is NULL here
>
Oh boy... Thanks for the feedback!
I'll put that on my priority list for tomorrow.
Regards,
Anthony
> With regards,
> Daniel
> --
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