On Tue, Jun 12, 2018 at 09:47:11PM +0300, Michael S. Tsirkin wrote:
> With this flag, kvm allows guest to control host CPU power state. This
> increases latency for other processes using same host CPU in an
> unpredictable way, but if decreases idle entry/exit times for the
> running VCPU.
>
> Follow-up patches will expose this capability to guest
> (using mwait leaf).
>
> Based on a patch by Wanpeng Li <kernellwp@xxxxxxxxx> .
>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> include/sysemu/sysemu.h | 1 +
> target/i386/kvm.c | 22 ++++++++++++++++++++++
> vl.c | 6 ++++++
> qemu-options.hx | 9 +++++++--
> 4 files changed, 36 insertions(+), 2 deletions(-)
>
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index e893f72f3b..b921c6f3b7 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -128,6 +128,7 @@ extern bool boot_strict;
> extern uint8_t *boot_splash_filedata;
> extern size_t boot_splash_filedata_size;
> extern bool enable_mlock;
> +extern bool enable_cpu_pm;
After looking at patch 2/2, I see that the global variable is
useful, and it's consistent with the existing enable_mlock
variable.
> extern uint8_t qemu_extra_params_fw[2];
> extern QEMUClockType rtc_clock;
> extern const char *mem_path;
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 44f70733e7..f093d55209 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1357,6 +1357,28 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
> smram_machine_done.notify = register_smram_listener;
> qemu_add_machine_init_done_notifier(&smram_machine_done);
> }
> +
> + if (enable_cpu_pm) {
> + int disable_exits = kvm_check_extension(s, KVM_CAP_X86_DISABLE_EXITS);
> + int ret;
> +
> +/* Work around for kernel header with a typo. TODO: fix header and drop. */
> +#if defined(KVM_X86_DISABLE_EXITS_HTL) && !defined(KVM_X86_DISABLE_EXITS_HLT)
> +#define KVM_X86_DISABLE_EXITS_HLT KVM_X86_DISABLE_EXITS_HTL
> +#endif
> + if (disable_exits) {
> + disable_exits &= (KVM_X86_DISABLE_EXITS_MWAIT |
> + KVM_X86_DISABLE_EXITS_HLT |
> + KVM_X86_DISABLE_EXITS_PAUSE);
> + }
> +
> + ret = kvm_vm_enable_cap(s, KVM_CAP_X86_DISABLE_EXITS, 0,
> + disable_exits);
Isn't the kvm_vm_enable_cap() call supposed to be inside the "if
(disable_exits)" block?
> + if (ret < 0) {
> + error_report("kvm: guest stopping CPU not supported: %s", strerror(-ret));
> + }
> + }
> +
> return 0;
> }
[...]
--
Eduardo
