Should -overcommit cpu-pm=on|off be converted to some machine sugar property?

Should -overcommit cpu-pm=on|off be converted to some machine sugar property?

[Philippe Mathieu-Daudé]

Hi Paolo,

I just noticed 'enable_cpu_pm' which seems architecture specific
option that ended into common code:

$ git grep -E 'cpu[_-]pm'
accel/tcg/user-exec-stub.c:5:bool enable_cpu_pm = false;
include/sysemu/sysemu.h:49:extern bool enable_cpu_pm;
Binary file pc-bios/skiboot.lid matches
qemu-options.hx:4196:    "-overcommit [mem-lock=on|off][cpu-pm=on|off]\n"
qemu-options.hx:4199:    "                cpu-pm=on|off controls cpu 
power management (default: off)\n",
qemu-options.hx:4204:``-overcommit cpu-pm=on|off``
qemu-options.hx:4214:    guest) can be enabled via ``cpu-pm=on`` 
(disabled by default). This
softmmu/globals.c:38:bool enable_cpu_pm;
softmmu/vl.c:350:            .name = "cpu-pm",
softmmu/vl.c:3440:                enable_cpu_pm = 
qemu_opt_get_bool(opts, "cpu-pm", false);
target/i386/host-cpu.c:44:static void host_cpu_enable_cpu_pm(X86CPU *cpu)
target/i386/host-cpu.c:88:    if (cpu->max_features && enable_cpu_pm) {
target/i386/host-cpu.c:89:        host_cpu_enable_cpu_pm(cpu);
target/i386/kvm/kvm-cpu.c:43:        if (enable_cpu_pm && 
kvm_has_waitpkg()) {
target/i386/kvm/kvm.c:390:        if (enable_cpu_pm) {
target/i386/kvm/kvm.c:2576:    if (enable_cpu_pm) {

Do we want to maintain this as a generic property or
can it be deprecated / converted to a machine-specific one?

Thanks,

Phil.

Re: Should -overcommit cpu-pm=on|off be converted to some machine sugar property?

[Michael S. Tsirkin]

On Mon, Dec 19, 2022 at 05:11:11PM +0100, Philippe Mathieu-Daudé wrote:
> Hi Paolo,
> 
> I just noticed 'enable_cpu_pm' which seems architecture specific
> option that ended into common code:
> 
> $ git grep -E 'cpu[_-]pm'
> accel/tcg/user-exec-stub.c:5:bool enable_cpu_pm = false;
> include/sysemu/sysemu.h:49:extern bool enable_cpu_pm;
> Binary file pc-bios/skiboot.lid matches
> qemu-options.hx:4196:    "-overcommit [mem-lock=on|off][cpu-pm=on|off]\n"
> qemu-options.hx:4199:    "                cpu-pm=on|off controls cpu power
> management (default: off)\n",
> qemu-options.hx:4204:``-overcommit cpu-pm=on|off``
> qemu-options.hx:4214:    guest) can be enabled via ``cpu-pm=on`` (disabled
> by default). This
> softmmu/globals.c:38:bool enable_cpu_pm;
> softmmu/vl.c:350:            .name = "cpu-pm",
> softmmu/vl.c:3440:                enable_cpu_pm = qemu_opt_get_bool(opts,
> "cpu-pm", false);
> target/i386/host-cpu.c:44:static void host_cpu_enable_cpu_pm(X86CPU *cpu)
> target/i386/host-cpu.c:88:    if (cpu->max_features && enable_cpu_pm) {
> target/i386/host-cpu.c:89:        host_cpu_enable_cpu_pm(cpu);
> target/i386/kvm/kvm-cpu.c:43:        if (enable_cpu_pm && kvm_has_waitpkg())
> {
> target/i386/kvm/kvm.c:390:        if (enable_cpu_pm) {
> target/i386/kvm/kvm.c:2576:    if (enable_cpu_pm) {
> 
> Do we want to maintain this as a generic property or
> can it be deprecated / converted to a machine-specific one?
> 
> Thanks,
> 
> Phil.

I don't care much.
ATM it only works well if you have a dedicated host CPU and memory, this
is why we put it in -overcommit.

-- 
MST

Re: Should -overcommit cpu-pm=on|off be converted to some machine sugar property?

[Paolo Bonzini]

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It's implemented only for x86, but it is not architecture-dependent. For
example on ARM you would implement it by mapping guest WFx to the host
instructions.

Paolo

Il lun 19 dic 2022, 17:11 Philippe Mathieu-Daudé <philmd@linaro.org> ha
scritto:

> Hi Paolo,
>
> I just noticed 'enable_cpu_pm' which seems architecture specific
> option that ended into common code:
>
> $ git grep -E 'cpu[_-]pm'
> accel/tcg/user-exec-stub.c:5:bool enable_cpu_pm = false;
> include/sysemu/sysemu.h:49:extern bool enable_cpu_pm;
> Binary file pc-bios/skiboot.lid matches
> qemu-options.hx:4196:    "-overcommit [mem-lock=on|off][cpu-pm=on|off]\n"
> qemu-options.hx:4199:    "                cpu-pm=on|off controls cpu
> power management (default: off)\n",
> qemu-options.hx:4204:``-overcommit cpu-pm=on|off``
> qemu-options.hx:4214:    guest) can be enabled via ``cpu-pm=on``
> (disabled by default). This
> softmmu/globals.c:38:bool enable_cpu_pm;
> softmmu/vl.c:350:            .name = "cpu-pm",
> softmmu/vl.c:3440:                enable_cpu_pm =
> qemu_opt_get_bool(opts, "cpu-pm", false);
> target/i386/host-cpu.c:44:static void host_cpu_enable_cpu_pm(X86CPU *cpu)
> target/i386/host-cpu.c:88:    if (cpu->max_features && enable_cpu_pm) {
> target/i386/host-cpu.c:89:        host_cpu_enable_cpu_pm(cpu);
> target/i386/kvm/kvm-cpu.c:43:        if (enable_cpu_pm &&
> kvm_has_waitpkg()) {
> target/i386/kvm/kvm.c:390:        if (enable_cpu_pm) {
> target/i386/kvm/kvm.c:2576:    if (enable_cpu_pm) {
>
> Do we want to maintain this as a generic property or
> can it be deprecated / converted to a machine-specific one?
>
> Thanks,
>
> Phil.
>
>

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Re: Should -overcommit cpu-pm=on|off be converted to some machine sugar property?

[Philippe Mathieu-Daudé]

On 20/12/22 09:16, Paolo Bonzini wrote:
> It's implemented only for x86, but it is not architecture-dependent. For 
> example on ARM you would implement it by mapping guest WFx to the host 
> instructions.

OK, thanks for clarifying!

>     Hi Paolo,
> 
>     I just noticed 'enable_cpu_pm' which seems architecture specific
>     option that ended into common code:
> 
>     $ git grep -E 'cpu[_-]pm'
>     accel/tcg/user-exec-stub.c:5:bool enable_cpu_pm = false;
>     include/sysemu/sysemu.h:49:extern bool enable_cpu_pm;
>     Binary file pc-bios/skiboot.lid matches
>     qemu-options.hx:4196:    "-overcommit
>     [mem-lock=on|off][cpu-pm=on|off]\n"
>     qemu-options.hx:4199:    "                cpu-pm=on|off controls cpu
>     power management (default: off)\n",
>     qemu-options.hx:4204:``-overcommit cpu-pm=on|off``
>     qemu-options.hx:4214:    guest) can be enabled via ``cpu-pm=on``
>     (disabled by default). This
>     softmmu/globals.c:38:bool enable_cpu_pm;
>     softmmu/vl.c:350:            .name = "cpu-pm",
>     softmmu/vl.c:3440:                enable_cpu_pm =
>     qemu_opt_get_bool(opts, "cpu-pm", false);
>     target/i386/host-cpu.c:44:static void host_cpu_enable_cpu_pm(X86CPU
>     *cpu)
>     target/i386/host-cpu.c:88:    if (cpu->max_features && enable_cpu_pm) {
>     target/i386/host-cpu.c:89:        host_cpu_enable_cpu_pm(cpu);
>     target/i386/kvm/kvm-cpu.c:43:        if (enable_cpu_pm &&
>     kvm_has_waitpkg()) {
>     target/i386/kvm/kvm.c:390:        if (enable_cpu_pm) {
>     target/i386/kvm/kvm.c:2576:    if (enable_cpu_pm) {
> 
>     Do we want to maintain this as a generic property or
>     can it be deprecated / converted to a machine-specific one?
> 
>     Thanks,
> 
>     Phil.
>