From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
To: kvm-devel <kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>
Subject: KVM and OS/2: #UD in real mode
Date: Tue, 22 Jan 2008 18:49:35 -0800 [thread overview]
Message-ID: <4796AB3F.5070407@zytor.com> (raw)
Just for fun, I tried to boot OS/2 Warp 4.0 under KVM (KVM-59 with the
latest git kernel from Linus as of yesterday, slightly post 2.6.24-rc8.)
I found that it crashes very early, apparently because KVM doesn't
handle an #UD received in user mode. It appears that OS/2 actually
provokes an #UD deliberately in real mode, from the disassembly it looks
like it's trying to probe for the 486 version of cmpxchg (which has a
different opcode than the 586+ version.)
It looks like the kernel code filters out a very small number of
real-mode exceptions, and does a KVM exit for all the other ones; the
userspace code then unconditionally barfs. This is presumably a
temporary hack; what is the intended behaviour - for this to be handled
in-kernel, or in userspace?
-hpa
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next reply other threads:[~2008-01-23 2:49 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-01-23 2:49 H. Peter Anvin [this message]
[not found] ` <4796AB3F.5070407-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
2008-01-24 6:33 ` KVM and OS/2: #UD in real mode Avi Kivity
[not found] ` <4798312D.9060204-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
2008-01-24 6:40 ` H. Peter Anvin
2008-03-06 12:40 ` Bjørn Mork
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