[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Loading a 32 bit kernel from 64 bit grub-xen
On Tue, 2014-07-01 at 14:27 -0400, Phillip Susi wrote: > On 7/1/2014 12:18 PM, Andrey Borzenkov wrote: > > Ð Tue, 01 Jul 2014 12:06:08 -0400 Phillip Susi <psusi@xxxxxxxxxx> > > ÐÐÑÐÑ: > > > >> -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 > > > >> I have been trying to fix grub to load a 32 bit kernel from the > >> 64 bit xen build. After fixing up one or two minor issues with > >> the elf loader, I believe I now have it to the point where it > >> jumps correctly to the 32 bit kernel and it crashes there, since > >> it is 32 bit code still executing on a cpu in 64 bit mode. The > >> question is how to return the cpu to 32 bit mode *under xen*? > > > > > > IIRC it was already discussed not long ago and it seems to be Xen > > limitation. You probably need to ask on xen-devel to be sure. > > > > Is it not more simple to use 32 bit grub with 32 bit kernel to > > start with? > > The problem with that is that you have to know in advance which kernel > you are going to boot. That makes configuring virtual hosts harder; > they just want one grub image they can use to chainload whatever the > guest wants to install in their domain. > > Also there must be a way to do this otherwise a 64 bit kernel running > under xen wouldn't be able to execute a 32 bit binary. I suppose I'll > Cc xen-devel. Running a 32-bit userspace under a 64-bit kernel is a very different thing to switching a kernel from 64-bit down to 32-bit (or vice versa). While the former is of course supported just fine the latter is not and IIRC doing so would be very difficult for a PV kernel due to the way the interfaces are constructed (e.g. to p2m entries change size, the maximum addressable machine address changes). Yes, this is a massive Pain In The A**. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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