06.02.2014 17:15, Ian Campbell wrote: > On Thu, 2014-02-06 at 17:08 +0400, Michael Tokarev wrote: >> 06.02.2014 12:50, Gerd Hoffmann wrote: [] >>> As far I know xen has its own seabios builds anyway as they >>> have to add hvmloader to the mix. Thats why it has been >>> turned off in the upstream blob builds, nobody will use these >>> with xen anyway. >> >> Thank you Gerd for the answer. Ian, can you give some light >> here, what is still missing in seabios for xen? Because, >> well, .. > > Nothing is missing in seabios. > > The above patch is a fix to Xen not SeaBIOS, which lets it work > correctly regardless of the size of the seabios binary. > > There is no need to do anything other than apply that fix to the Xen > packages (perhaps by upgrading to 4.3.1) AFAIK.
Okay. That is good to know, because it started to become quite confusing :) Yes I understand the xen hvmloader change is necessary for xen to support larger bios sizes, and new full-blown bios is larger than 128Kb. [] >> (And yes I know about >> >> http://xenbits.xen.org/gitweb/?p=xen.git;a=commit;h=5f2875739beef3a75c7a7e8579b6cbcb464e61b3 >> which talks about >128kb bios size. This is actually exactly >> the same issue which I'm trying to address now, from a few PoVs: >> qemu now builds/uses stripped-down bios for older (pre-2.0) machine >> types, and that stripped-down version does not include Xen bits >> in order to fit in 128Kb, because with xen it doesn't fit anymore. >> Maybe we should start building special xen variant of seabios -- >> stripped down but WITH xen. Oh well.) > > Why is this stripped down SeaBIOS needed? Because it fits into 128Kb, while complete build doesn't. And when the bios size grows (provided that software - xen and qemu - actually support this), it breaks guest migration between old and new systems. > Is there some reason the Xen build can't pickup the non-stripped down > (post-2.0) SeaBIOS? The question is exactly about old systems. Qemu has an option, -M foo. Right now, if foo is less than 2.0 (the upcoming release), it picks up the old small and now stripped-down verion of seabios. For new versions - like -M pc-2.0, or by default - it uses the new larger bios with all features. But I've no idea if xen actually uses or cares about -M to start with. Qemu supports it for 2 things: migration, and keeping, say, windows guests activated across version changes (with variable success on both fronts :) Thanks, /mjt
