[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] FreeBSD boot loader on VT-x based Xen system

Andy Clayton wrote:
Randy Thelen wrote:
Folks --

I'm trying to run FreeBSD 6.0 on a VT-x based Xen system. I'm experiencing a problem where the boot loader is crashing before the FreeBSD kernel (proper) is loaded.

I don't think I can help you much as far as fixing, but earlier I opened a bug report in Bugzilla regarding this issue at http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=622 I will try to help any way I can but I have next to no experience with assembly. Time to learn, perhaps.

Good luck for now and ask if you would like some help (with something I can actually help with...),
Andy Clayton

Hey there is a patch that was mailed to -devel by Kevin Tronkowski today called "[Xen-devel] [PATCH] Extensions to vmxassist to handle additional mode switch cases". It sounds promising.
If I may quote:

Attached is a patch which extends vmxassist to handle two cases related to mode switching found while experimenting with different boot loaders.

The first case is use of the JMP instruction with memory location operands to complete a switch to protected mode. This patch adds emulation for this form of the JMP instruction to vmxassist.

The second case is where boot loader code does not save/restore a non-zero SS register across a protected mode traversal. Zeroing the SS register in vmxassist results in all sorts of problems in the domU after returning back to real mode. This patch stores segment register values before entering protected mode and correctly restores the old values (instead of an incorrect zero value) when reentering real mode. The first case is what I was looking at. I'll see if I can check this out shortly...

Andy Clayton

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.