Hi All, I am looking into the get_page() function implementation in Xen where I encounter the reference to _domain nd = page->u.inuse._domain; what this field is used for? I found comment in source ode about it /* Meaning of the _domain field in shadow pages * -------------------------------------------- * * In shadow pages, this field will always have its least significant bit * set. This ensures that all attempts to get_page() will fail (as all * valid pickled domain pointers have a zero for their least significant bit). * Instead, the remaining upper bits are used to record the shadow generation * counter when the shadow was created. */ But I am not able to understand this.What is actual significance of this variable? Please provide your valuable replies. jeet __________________________________________________________ Yahoo! India Answers: Share what you know. Learn something new http://in.answers.yahoo.com/ _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
At 13:55 +0530 on 27 Mar (1175003752), jeet wrote:> nd = page->u.inuse._domain; > > what this field is used for?The comment beside the definition of the field says: /* Owner of this page (NULL if page is anonymous). */> /* Meaning of the _domain field in shadow pages > * -------------------------------------------- > * > * In shadow pages, this field will always have its least significant bit > * set. This ensures that all attempts to get_page() will fail (as all > * valid pickled domain pointers have a zero for their least significant bit). > * Instead, the remaining upper bits are used to record the shadow generation > * counter when the shadow was created. > */This comment is from 3.0.4 and was never very useful, as IIRC the generation cuonters it refers to were never implemented in the main tree. Shadow pages have their own entirely separate version of the page_info struct now. Cheers, Tim. -- Tim Deegan <Tim.Deegan@xensource.com>, XenSource UK Limited Registered office c/o EC2Y 5EB, UK; company number 05334508 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Thanks Tim for reply I am looking into 3.0.3 version of xen does in this code the comment stand valid? or comment was regarding future implementation. jeet ----- Original Message ---- From: Tim Deegan <Tim.Deegan@xensource.com> To: jeet <jeet_sat12@yahoo.co.in> Cc: xen-devel@lists.xensource.com Sent: Tuesday, 27 March, 2007 2:07:31 PM Subject: Re: [Xen-devel] _domain in page_info structure At 13:55 +0530 on 27 Mar (1175003752), jeet wrote:> nd = page->u.inuse._domain; > > what this field is used for?The comment beside the definition of the field says: /* Owner of this page (NULL if page is anonymous). */> /* Meaning of the _domain field in shadow pages > * -------------------------------------------- > * > * In shadow pages, this field will always have its least significant bit > * set. This ensures that all attempts to get_page() will fail (as all > * valid pickled domain pointers have a zero for their least significant bit). > * Instead, the remaining upper bits are used to record the shadow generation > * counter when the shadow was created. > */This comment is from 3.0.4 and was never very useful, as IIRC the generation cuonters it refers to were never implemented in the main tree. Shadow pages have their own entirely separate version of the page_info struct now. Cheers, Tim. -- Tim Deegan <Tim.Deegan@xensource.com>, XenSource UK Limited Registered office c/o EC2Y 5EB, UK; company number 05334508 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel __________________________________________________________ Yahoo! India Answers: Share what you know. Learn something new http://in.answers.yahoo.com/ _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
At 15:15 +0530 on 27 Mar (1175008506), jeet wrote:> I am looking into 3.0.3 version of xen > does in this code the comment stand valid?IIRC 3.0.3 was the same. Why are you using such an old version if you''re interested in HVM? Tim. -- Tim Deegan <Tim.Deegan@xensource.com>, XenSource UK Limited Registered office c/o EC2Y 5EB, UK; company number 05334508 _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel