From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH 00/13] Add VMX TSC scaling support
Date: Mon, 28 Sep 2015 11:51:17 +0100
Message-ID: <56091BA5.8090604@citrix.com>
References: <1443424438-13404-1-git-send-email-haozhong.zhang@intel.com>
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To: Haozhong Zhang <haozhong.zhang@intel.com>, xen-devel@lists.xen.org
Cc: Kevin Tian <kevin.tian@intel.com>, Wei Liu <wei.liu2@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Jun Nakajima <jun.nakajima@intel.com>, Ian Jackson <ian.jackson@eu.citrix.com>, Aravind Gopalakrishnan <Aravind.Gopalakrishnan@amd.com>, Jan Beulich <jbeulich@suse.com>, Keir Fraser <keir@xen.org>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
List-Id: xen-devel@lists.xenproject.org

On 28/09/15 08:13, Haozhong Zhang wrote:
> This patchset adds support for VMX TSC scaling feature which is
> available on Intel Skylake CPU. The specification of VMX TSC scaling
> can be found at
> http://www.intel.com/content/www/us/en/processors/timestamp-counter-scaling-virtualization-white-paper.html
>
> VMX TSC scaling allows guest TSC which is read by guest rdtsc(p)
> instructions increases in a rate that is customized by the hypervisor
> and can be different than the host TSC rate. Basically, VMX TSC
> scaling adds a 64-bit field called TSC multiplier in VMCS so that, if
> VMX TSC scaling is enabled, TSC read by guest rdtsc(p) instructions
> will be calculated by the following formula:
>
>   guest EDX:EAX = (Host TSC * TSC multiplier) >> 48 + VMX TSC Offset
>
> where, Host TSC = Host MSR_IA32_TSC + Host MSR_IA32_TSC_ADJUST.
>
> This patchset is composed of following four parts.
>   1. PATCH 01 - 02 fix bugs in tsc_get_info() which could result in
>      errors when VMX TSC scaling is used.
>      
>   2. PATCH 03 - 09 add/move the common parts of VMX TSC scaling and
>      SVM TSC ratio to hvm.c and x86/time.c.
>      
>   3. PATCH 10 - 12 implement the VMX-specific code for supporting VMX
>      TSC scaling.
>      
>   4. PATCH 13 adapts libxl for VMX TSC scaling (as well as SVM TSC
>      ratio).

Thankyou for this series.  I have had a brief look over it and it
appears to be in good shape, but have not done a thorough review yet.

Konrad/Boris: As Oracle are the main users of the more interesting guest
timing modes, do you have tests to verify correct functioning?

~Andrew