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: Tue, 23 Feb 2016 07:10:07 -0700
Message-ID: <56CC764F02000078000D53C9@prv-mh.provo.novell.com>
References: <1456193104-12761-1-git-send-email-haozhong.zhang@intel.com>
	<1456193104-12761-2-git-send-email-haozhong.zhang@intel.com>
	<56CC65F4.4070803@oracle.com>
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To: Haozhong Zhang <haozhong.zhang@intel.com>, Boris Ostrovsky <boris.ostrovsky@oracle.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>
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>>> On 23.02.16 at 15:00, <boris.ostrovsky@oracle.com> wrote:
> On 02/22/2016 09:04 PM, Haozhong Zhang wrote:
> 
>>   
>> +    if ( cpu_has_tsc_ratio )
>> +        svm_function_table.tsc_scaling.ratio_frac_bits = 32;
>> +
> 
> 
>>   
>> +#define hvm_tsc_scaling_supported \
>> +    (!!hvm_funcs.tsc_scaling.ratio_frac_bits)
>> +
> 
> What is the difference (in usage) between cpu_has_tsc_ratio and 
> hvm_tsc_scaling_supported? Isn't the first imply the second (and if yes 
> then what's the reason for having the latter)?

Iiuc cpu_has_tsc_ratio is AMD/SVM specific, while
hvm_tsc_scaling_supported is meant to be vendor independent.

Jan