Re: [Qemu-devel] Re: backdoor

[Anthony Liguori]

On 10/25/2010 08:37 AM, Lluís wrote:
> Paolo Bonzini writes:
>
>    
> > On 10/25/2010 12:54 PM, Lluís wrote:
> >      
> > > * Backdoor channels need to provide arguments.
> > > * It's better to provide the same mechanism for both *-user and softmmu
> > > (otherwise the application to simulate or the interposed librariy
> > > should be compiled differently on every case).
> > >        
>    
> > You can add the syscall and, if it returns with ENOSYS, fall back to MMIO/PIO
> > (you don't really need a special driver, only some chmod since BARs are
> > accessible from /sys) or watchpoint/breakpoint.
> >      
> That sounds nice, but would only work with Linux. I, for example, did
> some full-system simulations with a QNX guest.
>
> I know extending the ISA is not nice at all, but I think that's much
> more maintainable than a per-guest OS interface (supposing some will
> need extra guest drivers).
>    

On x86, there are some architecturally nicer ways to do this.

For instance, a CPUID leaf could be used in the 0x40001xxx range.

Regards,

Anthony Liguori