RE: [Xen-devel] Re: [PATCH][HVM] Inject #GP for un-emulated instructions rather than crash guest

["Nakajima, Jun" <jun.nakajima@xxxxxxxxx>]

Keir Fraser wrote:
> Okay, but would #UD be a better exception to deliver in this case?
Less
> overloaded than #GP and more appropriate?

Since delivering #UD would provide more hints for guests to detect
inconsistency (i.e. incomplete emulation) with instruction handling in
the VM, I think delivering #GP should be more appropriate as a
workaround.

> 
>  -- Keir
> 
> On 27/11/07 04:37, "Cui, Dexuan" <dexuan.cui@xxxxxxxxx> wrote:
> 
> > The CrashMe stress test (a process repeatedly forks child processes,
and
> > the child processes initialize a buffer with random numbers, then
treat
> > the buffer as code, and execute it) can crash 32-bit HVM RHEL5.1
guest
> > easily; this is because we haven't emulated all the instructions in
> > handle_mmio() yet. 
> > 
> > The CrashMe process runs with root rights, and can access MMIO space
in
> > an unknown way ("strace -f" shows the random codes running at CPL=3
> > don't call mmap(), and don't open any special files in /dev/ "); the
gpa
> > may look like 0xa**** or  0xb****, or 0xfee0****.
> > After running CrashMe for several hours, I have found 24 un-emulated
> > instructions may be hit... 
> > 
> > This patch may serve as a workaround.
> > 
> > Signed-off-by: Dexuan Cui <dexuan.cui@xxxxxxxxx>
> > 
> 

Jun
---
Intel Open Source Technology Center

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