On Mon, Sep 28, 2015 at 08:28:57PM -0700, Eric Northup wrote:
> On Sun, Sep 27, 2015 at 10:38 PM, Haozhong Zhang
> <haozhong.zhang@xxxxxxxxx> 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@xxxxxxxxx>
> > ---
> > 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.
>
You are right. I'll remove kvm_tsc_scaling_ratio_rsvd and just use
kvm_max_tsc_scaling_ratio to verify TSC scaling ratio in
set_tsc_khz().
> >
> > 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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