Re: [PATCH] deal with interrupt shadow state for emulated instruction

[Avi Kivity]

H. Peter Anvin wrote:
> Avi Kivity wrote:
>   
> > Why do we care?  The guest can only harm itself, and if it wants to
> > disable interrupts, it would be a lot easier for it to run a plain 'cli'.
> >
> > I guess it would be a problem if we emulated 'mov ss' for ordinary
> > userspace or vm86 mode, but we don't.
> >
> >     
>
> Well, the answer is that mov ss is an unprivileged instruction.
>
>   

We don't emulate guest user mode.

Well, if guest userspace can convince its kernel to give it access to 
some memory mapped I/O register, I guess it can execute repeated 'mov 
ss, mmio' and starve the guest kernel.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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