linux-kernel - Re: KVM guest-kernel panics double fault

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Date:	Sun, 08 Jan 2012 03:31:57 +0100
From:	Stephan Bärwolf <stephan.baerwolf@...ilmenau.de>
To:	Avi Kivity <avi@...hat.com>
CC:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: KVM guest-kernel panics double fault

Hello, it is me again...

I improved the patch, so it is now working on bases of guest's pretends.
(For AMD and INTEL CPUs)
If anybody needs it, I can also publish my test-VM - just ask me...

On 12/29/11 11:04, Avi Kivity wrote:
> The PROT32 check should be qualifed by a checking the the guest cpuid
> vendor is not AMD.  Otherwise a guest that was migrated from an AMD host
> to an Intel host (this is what this emulation was written for in the
> first place) will #UD unexpectedly.
>
There are strange AMDs out there, where also again legacy-mode
syscalls are not available - or even syscall at all is not available.
The implemented (according to doku) tests should now cover all
cases.

I also think I ovserved some strange behaviour according to cpuid after
migration (change from Intel to AMD - see picture:
http://matrixstorm.com/software/linux/kvm/20111229/cpuidmagic.jpg )
But it is possible it is "only" an qemu-kvm (0.14.1-r2) bug ...

The patch I wrote is against 3.2, but I always tested with linux 3.1.7.
Hopfully it solve the problems to your satisfaction this time.

regards Stephan

View attachment "0001-KVM-move-emul_to_vcpu-makro-to-headerfile.patch" of type "text/x-patch" (1403 bytes)

View attachment "0002-KVM-fix-missing-illegal-instruction-trap-in-protecte.patch" of type "text/x-patch" (6094 bytes)