From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH V5 07/12] xen: Introduce monitor_op domctl
Date: Tue, 17 Feb 2015 18:37:24 +0000
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To: Tamas K Lengyel <tamas.lengyel@zentific.com>, Jan Beulich <JBeulich@suse.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>, "wei.liu2@citrix.com" <wei.liu2@citrix.com>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Steven Maresca <steve@zentific.com>, Tim Deegan <tim@xen.org>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>, "Dong,
	Eddie" <eddie.dong@intel.com>, Andres Lagar-Cavilla <andres@lagarcavilla.org>, Jun Nakajima <jun.nakajima@intel.com>, "rshriram@cs.ubc.ca" <rshriram@cs.ubc.ca>, Keir Fraser <keir@xen.org>, Daniel De Graaf <dgdegra@tycho.nsa.gov>, "yanghy@cn.fujitsu.com" <yanghy@cn.fujitsu.com>, Ian Jackson <ian.jackson@eu.citrix.com>
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On 17/02/15 18:20, Tamas K Lengyel wrote:
> +/************************************************/
> +/*            monitor event options             */
> +/************************************************/
> +struct mov_to_cr {
> +    uint8_t enabled;
> +    uint8_t sync;
> +    uint8_t onchangeonly;
> +};
> +
> +struct mov_to_msr {
> +    uint8_t enabled;
> +    uint8_t extended_capture;
> +};
> +
> +struct debug_event {
> +    uint8_t enabled;
> +};
>> These are all internal structures - is there anything wrong with using
>> bitfields here?
> The use if bitfields is not good performance-wise AFAIK. Would there
> be any benefit that would offset that?

struct vcpu lives in a 4k page.  We avoid needlessly bloating it.

However bitfields will not work with my suggestion as you cannot
construct a pointer to 'enabled' if enabled is a bit.

~Andrew