From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH v5 1/6] x86/hvm: Collect information of TSC
 scaling ratio
Date: Wed, 24 Feb 2016 07:36:35 -0700
Message-ID: <56CDCE0302000078000D5B93@prv-mh.provo.novell.com>
References: <1456193104-12761-1-git-send-email-haozhong.zhang@intel.com>
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To: Haozhong Zhang <haozhong.zhang@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Keir Fraser <keir@xen.org>, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>, Andrew Cooper <andrew.cooper3@citrix.com>, xen-devel@lists.xen.org, Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>, Jun Nakajima <jun.nakajima@intel.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>
List-Id: xen-devel@lists.xenproject.org

>>> On 23.02.16 at 03:04, <haozhong.zhang@intel.com> wrote:
> Both VMX TSC scaling and SVM TSC ratio use the 64-bit TSC scaling ratio,
> but the number of fractional bits of the ratio is different between VMX
> and SVM. This patch adds the architecture code to collect the number of
> fractional bits and other related information into fields of struct
> hvm_function_table so that they can be used in the common code.
> 
> Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>

albeit I would have wished ...

> @@ -312,8 +311,8 @@ void hvm_set_guest_tsc_fixed(struct vcpu *v, u64 guest_tsc, u64 at_tsc)
>      else
>      {
>          tsc = at_tsc ?: rdtsc();
> -        if ( cpu_has_tsc_ratio )
> -            tsc = hvm_funcs.scale_tsc(v, tsc);
> +        if ( hvm_tsc_scaling_supported )
> +            tsc = hvm_funcs.tsc_scaling.scale_tsc(v, tsc);

... for these to get their redundancy reduced, .e.g

            tsc = hvm_funcs.tsc_scaling.scale(v, tsc);

The R-b may be retained if you elect to make that adjustment.

Jan