Re: [RFC PATCH 0/3] Add segment limit checks to emulator

[Stefan Hajnoczi <stefanha@gmail.com>]

On Wed, Jul 7, 2010 at 10:23 PM, Mohammed Gamal <m.gamal005@gmail.com> wrote:
> After some conversation with Avi concerning why unreal mode has been seen to work
> with KVM on Intel. It clears out the scenario is caused as follows:
>
> - guest enters big real mode
> - kvm squashes limit to 64k-1
> - guest executes instructions with offset > 64k
> - cpu issues #GP due to limit violation
> - kvm handle_rmode_exception() -> emulator
> - emulator ignores limit, emulates instruction
>
> With these applied I am getting vmentry failures with SeaBIOS and
> gPXE. So it's needless to say that these patches are not meant for merging!

Thanks for testing with gPXE and please don't hesitate to discuss
issues you hit with gPXE on gpxe-devel@etherboot.org.  I look forward
to your big real mode work :).

> Mohammed Gamal (3):
>  Add helper methods to get segment limits
>  x86 emulator: Add cs_base() helper
>  x86 emulator: Add segment limit checks and helper functions
>
>  arch/x86/include/asm/kvm_emulate.h |    1 +
>  arch/x86/include/asm/kvm_host.h    |    1 +
>  arch/x86/kvm/emulate.c             |  123 +++++++++++++++++++++++++++++-------
>  arch/x86/kvm/svm.c                 |    8 +++
>  arch/x86/kvm/vmx.c                 |    8 +++
>  arch/x86/kvm/x86.c                 |   12 ++++
>  6 files changed, 130 insertions(+), 23 deletions(-)
>
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Stefan