2009/10/11 andi <andi.platschek@xxxxxxxxx>: > Ozan Türkyılmaz wrote: >> >> hey all, >> >> it's not really kernel reletad but, kernel peaple should be trasted >> with hardware questions. >> >> my question is this: today a lot of CPUs (x36 based ones) come with >> visualization extensions and >> a lot of visualization software supports this extensions. my >> question is that this visualization extensions >> can really make difference of performance of guest OS. >> >> ps: i got AMD 64 cpu with AMD-V extensions. >> >> > > I think, what you are talking about is virtualization, not visualization? > > And, yes these extensions really speed up virtualization, the reason for > this is, that a guest OS that > is running in Ring3 (unprivileged mode) is not allowed to do the priviledged well....i am not sure of all scenario...but i can describe what i know.... Say VMWare. In normal OS only ring 0 and 3 are used. So VMware used ring 1 to emulate the guest's higher privilege mode, and ring 3 for the application. Same design with Xen, Lguest too. But if u are running in HVM mode, a higher privilege than ring 0 (called ring -1) is used for the hypervisor (or host) OS, and ring 0 for the guest OS. but QEMU may be different....not sure....possibly the same design with UML too....which is emulating everything in ring 3???? not sure of details.... > operations. If you do not have > a hardware support for virtualization, these priviledged operations have to > be emulated in software, which > is really slow. > > regards, > andi > > -- > To unsubscribe from this list: send an email with > "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx > Please read the FAQ at http://kernelnewbies.org/FAQ > > -- Regards, Peter Teoh -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
