Re: [Xen-devel] [PATCH v2 10/14] x86/hvm: Replace architecture TSC scaling by a common function

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

On 12/07/15 13:55, Boris Ostrovsky wrote:
> On 12/06/2015 03:58 PM, Haozhong Zhang wrote:
> >This patch implements a common function hvm_scale_tsc() to scale TSC by
> >using TSC scaling information collected by architecture code.
> >
> >Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
> >---
> >  xen/arch/x86/hvm/hvm.c        | 18 +++++++++--
> >  xen/arch/x86/hvm/svm/svm.c    | 12 --------
> >  xen/arch/x86/time.c           |  2 +-
> >  xen/include/asm-x86/hvm/hvm.h |  3 +-
> >  xen/include/asm-x86/math64.h  | 70 
> > +++++++++++++++++++++++++++++++++++++++++++
> >  5 files changed, 88 insertions(+), 17 deletions(-)
> >
> >diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> >index 52a0ef8..1e3d89f 100644
> >--- a/xen/arch/x86/hvm/hvm.c
> >+++ b/xen/arch/x86/hvm/hvm.c
> >@@ -302,6 +302,20 @@ int hvm_set_guest_pat(struct vcpu *v, u64 guest_pat)
> >      return 1;
> >  }
> >+u64 hvm_scale_tsc(const struct vcpu *v, u64 tsc)
> >+{
> >+    u64 ratio = v->arch.hvm_vcpu.tsc_scaling_ratio;
> >+
> >+    if ( !hvm_funcs.tsc_scaling_supported ||
> >+         ratio == hvm_funcs.default_tsc_scaling_ratio )
> >+        return tsc;
> >+
> >+    BUG_ON(hvm_funcs.tsc_scaling_ratio_frac_bits >= 64 ||
> >+           hvm_funcs.tsc_scaling_ratio_frac_bits == 0);
> 
> Since these values never change, I am not sure it's worth testing this. And
> if you think it is then I'd do it somewhere in initialization code.
>

I'll remove this unnecessary check.

> >+
> >+    return mul_u64_u64_shr(tsc, ratio, 
> >hvm_funcs.tsc_scaling_ratio_frac_bits);
> >+}
> >+
> 
> 
> 
> >diff --git a/xen/include/asm-x86/math64.h b/xen/include/asm-x86/math64.h
> >index 9af6aee..c6a472b 100644
> >--- a/xen/include/asm-x86/math64.h
> >+++ b/xen/include/asm-x86/math64.h
> >@@ -27,4 +27,74 @@ static inline u64 mul_u64_u32_div(u64 a, u32 mul, u32 
> >divisor)
> >      return rl.ll;
> >  }
> >+/*
> >+ * Multiply two 64-bit unsigned integers a and b. The most and least
> >+ * significant 64 bits of the 128-bit result are returned through hi
> >+ * and lo respectively.
> >+ */
> >+static inline void mul64(u64 *lo, u64 *hi, u64 a, u64 b)
> 
> Please move these routines (as well as one in previous patch into a
> standalone math patch (and provide attribution to wherever they came from).
>

I'll move them to a standalone patch and add comments for their source.

Thanks,
Haozhong

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel