Re: [Qemu-devel] [PATCH] kvm: support guest access CORE cstate

[Paolo Bonzini <pbonzini@redhat.com>]

On 21/05/19 08:17, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
> 
> Allow guest reads CORE cstate when exposing host CPU power management capabilities 
> to the guest. PKG cstate is restricted to avoid a guest to get the whole package 
> information in multi-tenant scenario.
> 
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Radim Krčmář <rkrcmar@redhat.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
>  linux-headers/linux/kvm.h | 4 +++-
>  target/i386/kvm.c         | 3 ++-
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> index b53ee59..d648fde 100644
> --- a/linux-headers/linux/kvm.h
> +++ b/linux-headers/linux/kvm.h
> @@ -696,9 +696,11 @@ struct kvm_ioeventfd {
>  #define KVM_X86_DISABLE_EXITS_MWAIT          (1 << 0)
>  #define KVM_X86_DISABLE_EXITS_HLT            (1 << 1)
>  #define KVM_X86_DISABLE_EXITS_PAUSE          (1 << 2)
> +#define KVM_X86_DISABLE_EXITS_CSTATE         (1 << 3)
>  #define KVM_X86_DISABLE_VALID_EXITS          (KVM_X86_DISABLE_EXITS_MWAIT | \
>                                                KVM_X86_DISABLE_EXITS_HLT | \
> -                                              KVM_X86_DISABLE_EXITS_PAUSE)
> +                                              KVM_X86_DISABLE_EXITS_PAUSE | \
> +                                              KVM_X86_DISABLE_EXITS_CSTATE)
>  
>  /* for KVM_ENABLE_CAP */
>  struct kvm_enable_cap {
> diff --git a/target/i386/kvm.c b/target/i386/kvm.c
> index 3b29ce5..49a0cc1 100644
> --- a/target/i386/kvm.c
> +++ b/target/i386/kvm.c
> @@ -1645,7 +1645,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>          if (disable_exits) {
>              disable_exits &= (KVM_X86_DISABLE_EXITS_MWAIT |
>                                KVM_X86_DISABLE_EXITS_HLT |
> -                              KVM_X86_DISABLE_EXITS_PAUSE);
> +                              KVM_X86_DISABLE_EXITS_PAUSE |
> +                              KVM_X86_DISABLE_EXITS_CSTATE);
>          }
>  
>          ret = kvm_vm_enable_cap(s, KVM_CAP_X86_DISABLE_EXITS, 0,
> 

Hi,

instead of this, with the new design I've proposed QEMU will have to
save/restore the MSRs, but otherwise no change is needed to
kvm_arch_init and to the KVM headers.

Paolo