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Re: [PATCH 01/12] KVM: x86: Collect information for setting TSC scaling ratio

From Eric Northup <digitaleric@google.com>
Newsgroups linux.kernel
Subject Re: [PATCH 01/12] KVM: x86: Collect information for setting TSC scaling ratio
Date 2015-09-29 05:30 +0200
Message-ID <qdTM6-2Kw-5@gated-at.bofh.it> (permalink)
References <qdzkm-4Rn-5@gated-at.bofh.it> <qdzkm-4Rn-25@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Sun, Sep 27, 2015 at 10:38 PM, Haozhong Zhang
<haozhong.zhang@intel.com> wrote:
>
> The number of bits of the fractional part of the 64-bit TSC scaling
> ratio in VMX and SVM is different. This patch makes the architecture
> code to collect the number of fractional bits and other related
> information into variables that can be accessed in the common code.
>
> Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 8 ++++++++
>  arch/x86/kvm/svm.c              | 5 +++++
>  arch/x86/kvm/x86.c              | 8 ++++++++
>  3 files changed, 21 insertions(+)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 2beee03..5b9b86e 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -965,6 +965,14 @@ extern bool kvm_has_tsc_control;
>  extern u32  kvm_min_guest_tsc_khz;
>  /* maximum supported tsc_khz for guests */
>  extern u32  kvm_max_guest_tsc_khz;
> +/* number of bits of the fractional part of the TSC scaling ratio */
> +extern u8   kvm_tsc_scaling_ratio_frac_bits;
> +/* reserved bits of TSC scaling ratio (SBZ) */
> +extern u64  kvm_tsc_scaling_ratio_rsvd;
> +/* default TSC scaling ratio (= 1.0) */
> +extern u64  kvm_default_tsc_scaling_ratio;
> +/* maximum allowed value of TSC scaling ratio */
> +extern u64  kvm_max_tsc_scaling_ratio;

Do we need all 3 of kvm_max_guest_tsc_khz, kvm_max_tsc_scaling_ratio,
and kvm_tsc_scaling_ratio_rsvd (since only SVM has reserved bits - and
just for complaining if the high bits are set, which can already be
expressed by max_tsc_scaling ratio)

kvm_max_tsc_scaling_ratio seems to be write-only.

>
>  enum emulation_result {
>         EMULATE_DONE,         /* no further processing */
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 94b7d15..eff7db7 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -963,7 +963,12 @@ static __init int svm_hardware_setup(void)
>                 max = min(0x7fffffffULL, __scale_tsc(tsc_khz, TSC_RATIO_MAX));
>
>                 kvm_max_guest_tsc_khz = max;
> +
> +               kvm_max_tsc_scaling_ratio = TSC_RATIO_MAX;
> +               kvm_tsc_scaling_ratio_frac_bits = 32;
> +               kvm_tsc_scaling_ratio_rsvd = TSC_RATIO_RSVD;
>         }
> +       kvm_default_tsc_scaling_ratio = TSC_RATIO_DEFAULT;
>
>         if (nested) {
>                 printk(KERN_INFO "kvm: Nested Virtualization enabled\n");
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 991466b..f888225 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -106,6 +106,14 @@ bool kvm_has_tsc_control;
>  EXPORT_SYMBOL_GPL(kvm_has_tsc_control);
>  u32  kvm_max_guest_tsc_khz;
>  EXPORT_SYMBOL_GPL(kvm_max_guest_tsc_khz);
> +u8   kvm_tsc_scaling_ratio_frac_bits;
> +EXPORT_SYMBOL_GPL(kvm_tsc_scaling_ratio_frac_bits);
> +u64  kvm_tsc_scaling_ratio_rsvd;
> +EXPORT_SYMBOL_GPL(kvm_tsc_scaling_ratio_rsvd);
> +u64  kvm_default_tsc_scaling_ratio;
> +EXPORT_SYMBOL_GPL(kvm_default_tsc_scaling_ratio);
> +u64  kvm_max_tsc_scaling_ratio;
> +EXPORT_SYMBOL_GPL(kvm_max_tsc_scaling_ratio);
>
>  /* tsc tolerance in parts per million - default to 1/2 of the NTP threshold */
>  static u32 tsc_tolerance_ppm = 250;
> --
> 2.4.8
>
> --
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Thread

[PATCH 00/12] KVM: x86: add support for VMX TSC scaling Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:40 +0200
  [PATCH 07/12] KVM: x86: Move TSC scaling logic out of call-back read_l1_tsc() Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:40 +0200
  [PATCH 11/12] KVM: VMX: Use a scaled host TSC for guest readings of MSR_IA32_TSC Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:40 +0200
  [PATCH 06/12] KVM: x86: Move TSC scaling logic out of call-back adjust_tsc_offset() Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:40 +0200
    Re: [PATCH 06/12] KVM: x86: Move TSC scaling logic out of call-back  adjust_tsc_offset() Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 22:20 +0200
      Re: [PATCH 06/12] KVM: x86: Move TSC scaling logic out of call-back  adjust_tsc_offset() Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-29 03:50 +0200
  [PATCH 01/12] KVM: x86: Collect information for setting TSC scaling ratio Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:40 +0200
    Re: [PATCH 01/12] KVM: x86: Collect information for setting TSC  scaling ratio Eric Northup <digitaleric@google.com> - 2015-09-29 05:30 +0200
      Re: [PATCH 01/12] KVM: x86: Collect information for setting TSC  scaling ratio Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-29 06:10 +0200
  [PATCH 02/12] KVM: x86: Add a common TSC scaling ratio field in kvm_vcpu_arch Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:50 +0200
    Re: [PATCH 02/12] KVM: x86: Add a common TSC scaling ratio field in  kvm_vcpu_arch Radim Krčmář <rkrcmar@redhat.com> - 2015-10-05 21:30 +0200
  [PATCH 08/12] KVM: x86: Use the correct vcpu's TSC rate to compute time scale Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:50 +0200
    Re: [PATCH 08/12] KVM: x86: Use the correct vcpu's TSC rate to  compute time scale Radim Krčmář <rkrcmar@redhat.com> - 2015-10-05 22:20 +0200
  [PATCH 05/12] KVM: x86: Replace call-back compute_tsc_offset() with a common function Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:50 +0200
  [PATCH 03/12] KVM: x86: Add a common TSC scaling function Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:50 +0200
    Re: [PATCH 03/12] KVM: x86: Add a common TSC scaling function Paolo Bonzini <pbonzini@redhat.com> - 2015-09-28 22:20 +0200
      Re: [PATCH 03/12] KVM: x86: Add a common TSC scaling function Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-29 04:00 +0200
  [PATCH 10/12] KVM: VMX: Setup TSC scaling ratio when a vcpu is loaded Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:50 +0200
  [PATCH 04/12] KVM: x86: Replace call-back set_tsc_khz() with a common function Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-28 07:50 +0200
    Re: [PATCH 04/12] KVM: x86: Replace call-back set_tsc_khz() with a  common function Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-29 05:50 +0200
    Re: [PATCH 04/12] KVM: x86: Replace call-back set_tsc_khz() with a  common function Radim Krčmář <rkrcmar@redhat.com> - 2015-10-05 22:00 +0200
      Re: [PATCH 04/12] KVM: x86: Replace call-back set_tsc_khz() with a  common function David Matlack <dmatlack@google.com> - 2015-10-05 22:50 +0200
  Re: [PATCH 00/12] KVM: x86: add support for VMX TSC scaling Haozhong Zhang <haozhong.zhang@intel.com> - 2015-09-29 06:10 +0200
  Re: [PATCH 00/12] KVM: x86: add support for VMX TSC scaling Eric Northup <digitaleric@google.com> - 2015-09-29 06:10 +0200

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