On 08/01/2010 12:24 PM, Gleb Natapov wrote:
On Sun, Aug 01, 2010 at 12:14:40PM +0300, Avi Kivity wrote:
On 08/01/2010 12:01 PM, Gleb Natapov wrote:
It uses rip _during_ pio. And pio emulation changes rip
only at the end of emulation.
But non-emulated pio does a skip_emulated_instruction() immediately
(or so the code in kvm-tpr-opt.c assumes:
Indeed, this is bug in non-emulated pio.
But userspace depends on this bug.
We can fix that, or make it smarter. Look for io instruction at
rip/rip-2 and use rip accordingly for instance.
That requires everyone to update, or suffer major breakage.
But the patch does not change
rip behaviour for emulated pio. vcpu->arch.emulate_ctxt.eip is updated
only at the end of emulation.
That will lead to failures if the emulator is used for the
kvm-tpr-opt pio (which may happen with big real mode).
IIRC it was always this way in emulator. I'd rather fix userspace than
break emulator.
It wasn't a problem because the emulator wasn't (and still isn't) used
for this. But it has the potential to break badly once we make
emulate_invalid_guest_state=1 the default.
--
error compiling committee.c: too many arguments to function
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