From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@suse.com>
Subject: Re: [PATCH 3/4] tools/libxc: Alow getting and setting
 the max sub C-State
Date: Wed, 18 Jun 2014 17:00:56 +0100
Message-ID: <53A1D3D8020000780001B994@mail.emea.novell.com>
References: <1403103855-23080-1-git-send-email-ross.lagerwall@citrix.com>
	<1403103855-23080-4-git-send-email-ross.lagerwall@citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <1403103855-23080-4-git-send-email-ross.lagerwall@citrix.com>
Content-Disposition: inline
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Ross Lagerwall <ross.lagerwall@citrix.com>
Cc: Keir Fraser <keir@xen.org>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Liu Jinsong <jinsong.liu@alibaba-inc.com>, Ian Jackson <ian.jackson@eu.citrix.com>, xen-devel@lists.xen.org
List-Id: xen-devel@lists.xenproject.org

>>> On 18.06.14 at 17:04, <ross.lagerwall@citrix.com> wrote:
> --- a/xen/include/public/sysctl.h
> +++ b/xen/include/public/sysctl.h
> @@ -366,6 +366,10 @@ struct xen_sysctl_pm_op {
>      #define XEN_SYSCTL_pm_op_enable_turbo               0x26
>      #define XEN_SYSCTL_pm_op_disable_turbo              0x27
>  
> +    /* cpuidle max_substate access command */
> +    #define XEN_SYSCTL_pm_op_get_max_substate     0x28
> +    #define XEN_SYSCTL_pm_op_set_max_substate     0x29
> +
>      uint32_t cmd;
>      uint32_t cpuid;
>      union {
> @@ -376,6 +380,8 @@ struct xen_sysctl_pm_op {
>          uint32_t                    set_sched_opt_smt;
>          uint32_t                    get_max_cstate;
>          uint32_t                    set_max_cstate;
> +        uint32_t                    get_max_substate;
> +        uint32_t                    set_max_substate;
>          uint32_t                    get_vcpu_migration_delay;
>          uint32_t                    set_vcpu_migration_delay;
>      } u;

I'm really uncertain about adding whole new sub-ops and union fields
for this. For simplicity's sake I'd simply re-use the ops and fields we
already have (with cpuid, which is unused anyway, distinguishing
between main and sub-states).

But then again now that I look at this from an interface perspective
I wonder whether sooner or later we wouldn't want to be able to
specify maximum sub-states per main state. That surely would
require separate new sub-ops (as it would likely require handles to
be passed in).

Jan