Date: Fri, 19 Mar 2010 22:10:35 -0600 From: Tim Judd <tajudd@gmail.com> To: Michael MacLeod <mikemacleod@gmail.com> Cc: freebsd-xen@freebsd.org Subject: Re: FreeBSD on Xen with hw virtualization support Message-ID: <ade45ae91003192110r774050dbld840aebcdfe7cb17@mail.gmail.com> In-Reply-To: <e8f0b581003190547u42de13c5u2613d76913af1db5@mail.gmail.com> References: <20100318204746.GA57903@cons.org> <e8f0b581003190547u42de13c5u2613d76913af1db5@mail.gmail.com>
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On 3/19/10, Michael MacLeod <mikemacleod@gmail.com> wrote: > Martin, > > Xen has support for two different kinds of guests. Paravirtualized guests > are aware that they are running inside a virtual environment, and have been > modified to operate well in this environment. All linux kernels above 2.6.27 > (I think) with the pv_ops extensions compiled in can run as a Xen VM in this > mode. This mode also does not require any particular CPU support. > > With proper CPU support Xen can also be a hypervisor style environment, in > which case the guest is not aware that it is running inside a virtual > environment. FreeBSD of any vintage can run successfully in this mode. > Unfortunately, there are greater performance penalties to running a guest in > HVM mode as opposed to PVM mode. > > Mike > > On Thu, Mar 18, 2010 at 4:47 PM, Martin Cracauer <cracauer@cons.org> wrote: > >> I never got this so I rather ask: >> >> Xen should run OS kernels unmodified (compared to their native >> hardware versions) if you have hardware virtualization support in the >> CPU. >> >> Why doesn't this cover FreeBSD? >> >> I am missing something here. >> >> Martin <SNIP> This is the first time I've heard of any penalty on HVM systems. What I'd like to know, given that I now have some googl'ing I need to do about this, is that for those who have already done this; how big is the impact? Is it so much that general usability and patience a sysadmin does not normally have would drive them insane? Is it similar to like the RCs or BETAs we put out with the WITNESS and all the debugging code? Appreciate any insight. --Tim
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