Hi, Does XEN have the concept of virtual TLBs? Regards, Sameer _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Sameer Ahuja wrote:> Hi, > > Does XEN have the concept of virtual TLBs? >Not really. Regards, Anthony Liguori> Regards, > Sameer > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel > >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
AMD will provide support for nested paging that caches address translations to reduce memory accesses in its latest quad-core CPUs. As the hypervisor can get pretty bogged down managing all of this and the processor is constantly switching from guest OS mode to hypervisor mode and back, Nesting page tables and caching memory addresses are ways of freeing things up as it cuts down on memory access time. So Xen may not need such kind of virtual TLB anymore. Liang ----- Original Message ----- From: "Anthony Liguori" <aliguori@us.ibm.com> To: "Sameer Ahuja" <sameer.ahuja@nechclst.in> Cc: "Tim Deegan" <Tim.Deegan@xensource.com>; <sameer.ahuja81@gmail.com>; <xen-devel@lists.xensource.com> Sent: Monday, November 20, 2006 9:53 AM Subject: Re: [Xen-devel] Vitrual TLBs> Sameer Ahuja wrote: >> Hi, >> >> Does XEN have the concept of virtual TLBs? >> > > Not really. > > Regards, > > Anthony Liguori > >> Regards, >> Sameer >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> >> > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Liang Yang wrote:> AMD will provide support for nested paging that caches address > translations > to reduce memory accesses in its latest quad-core CPUs. As the hypervisor > can get pretty bogged down managing all of this and the processor is > constantly switching from guest OS mode to hypervisor mode and back, > Nesting > page tables and caching memory addresses are ways of freeing things up > as it > cuts down on memory access time. > > So Xen may not need such kind of virtual TLB anymore.If by virtual TLB you are actually referring to shadow paging (and I would argue that they are very different concepts), then sorry, I misunderstood the initial question. Yes, Xen supports shadow paging. Both Intel and AMD are planning on supporting hardware shadow paging too in future processors. I think it remains to be see if the hardware shadow paging is flexible enough to totally replace software shadow paging. Regards, Anthony Liguori> Liang > > ----- Original Message ----- > From: "Anthony Liguori" <aliguori@us.ibm.com> > To: "Sameer Ahuja" <sameer.ahuja@nechclst.in> > Cc: "Tim Deegan" <Tim.Deegan@xensource.com>; <sameer.ahuja81@gmail.com>; > <xen-devel@lists.xensource.com> > Sent: Monday, November 20, 2006 9:53 AM > Subject: Re: [Xen-devel] Vitrual TLBs > > >> Sameer Ahuja wrote: >>> Hi, >>> >>> Does XEN have the concept of virtual TLBs? >>> >> >> Not really. >> >> Regards, >> >> Anthony Liguori >> >>> Regards, >>> Sameer >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@lists.xensource.com >>> http://lists.xensource.com/xen-devel >>> >>> >> >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Hi Liang, Can you please share some more knowledge on this topic? How these virtual TLB''s are implemented? Regards, Sameer -----Original Message----- From: xen-devel-bounces@lists.xensource.com [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Liang Yang Sent: Monday, November 20, 2006 10:53 PM To: Anthony Liguori; Sameer Ahuja Cc: Tim Deegan; sameer.ahuja81@gmail.com; xen-devel@lists.xensource.com Subject: Re: [Xen-devel] Vitrual TLBs AMD will provide support for nested paging that caches address translations to reduce memory accesses in its latest quad-core CPUs. As the hypervisor can get pretty bogged down managing all of this and the processor is constantly switching from guest OS mode to hypervisor mode and back, Nesting page tables and caching memory addresses are ways of freeing things up as it cuts down on memory access time. So Xen may not need such kind of virtual TLB anymore. Liang ----- Original Message ----- From: "Anthony Liguori" <aliguori@us.ibm.com> To: "Sameer Ahuja" <sameer.ahuja@nechclst.in> Cc: "Tim Deegan" <Tim.Deegan@xensource.com>; <sameer.ahuja81@gmail.com>; <xen-devel@lists.xensource.com> Sent: Monday, November 20, 2006 9:53 AM Subject: Re: [Xen-devel] Vitrual TLBs> Sameer Ahuja wrote: >> Hi, >> >> Does XEN have the concept of virtual TLBs? >> > > Not really. > > Regards, > > Anthony Liguori > >> Regards, >> Sameer >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> >> > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel >_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
No Anthony, I didn''t refer to shadow paging. I meant virtual TLB''s only. I know that shadow tables are maintained in XEN. -----Original Message----- From: Anthony Liguori [mailto:aliguori@us.ibm.com] Sent: Tuesday, November 21, 2006 1:31 AM To: Liang Yang Cc: Sameer Ahuja; Tim Deegan; sameer.ahuja81@gmail.com; xen-devel@lists.xensource.com Subject: Re: [Xen-devel] Vitrual TLBs Liang Yang wrote:> AMD will provide support for nested paging that caches address > translations > to reduce memory accesses in its latest quad-core CPUs. As thehypervisor> can get pretty bogged down managing all of this and the processor is > constantly switching from guest OS mode to hypervisor mode and back, > Nesting > page tables and caching memory addresses are ways of freeing things up> as it > cuts down on memory access time. > > So Xen may not need such kind of virtual TLB anymore.If by virtual TLB you are actually referring to shadow paging (and I would argue that they are very different concepts), then sorry, I misunderstood the initial question. Yes, Xen supports shadow paging. Both Intel and AMD are planning on supporting hardware shadow paging too in future processors. I think it remains to be see if the hardware shadow paging is flexible enough to totally replace software shadow paging. Regards, Anthony Liguori> Liang > > ----- Original Message ----- > From: "Anthony Liguori" <aliguori@us.ibm.com> > To: "Sameer Ahuja" <sameer.ahuja@nechclst.in> > Cc: "Tim Deegan" <Tim.Deegan@xensource.com>;<sameer.ahuja81@gmail.com>;> <xen-devel@lists.xensource.com> > Sent: Monday, November 20, 2006 9:53 AM > Subject: Re: [Xen-devel] Vitrual TLBs > > >> Sameer Ahuja wrote: >>> Hi, >>> >>> Does XEN have the concept of virtual TLBs? >>> >> >> Not really. >> >> Regards, >> >> Anthony Liguori >> >>> Regards, >>> Sameer >>> >>> _______________________________________________ >>> Xen-devel mailing list >>> Xen-devel@lists.xensource.com >>> http://lists.xensource.com/xen-devel >>> >>> >> >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@lists.xensource.com >> http://lists.xensource.com/xen-devel >> > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel_______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel