From mboxrd@z Thu Jan  1 00:00:00 1970
From: Marcelo Tosatti <mtosatti@redhat.com>
Subject: Re: KVM: x86: stop IO emulation cycle if instruction pointer is
 modified
Date: Mon, 8 Jul 2013 18:16:35 -0300
Message-ID: <20130708211635.GA11148@amt.cnet>
References: <20130705191654.GA18788@amt.cnet>
 <20130706074112.GA26728@redhat.com>
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Cc: kvm-devel <kvm@vger.kernel.org>
To: Gleb Natapov <gleb@redhat.com>
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On Sat, Jul 06, 2013 at 10:41:12AM +0300, Gleb Natapov wrote:
> On Fri, Jul 05, 2013 at 04:16:55PM -0300, Marcelo Tosatti wrote:
> > 
> > MMIO/PIO emulation should be interrupted if the system is restarted.
> > Otherwise in progress IO emulation continues at the instruction pointer,
> > even after vcpus' IP has been modified by KVM_SET_REGS.
> > 
> > Use IP change as an indicator to reset MMIO/PIO emulation state.
> > 
> Userspace has to return to the kernel to complete pending IO operation.
> This is documented in Documentation/virtual/kvm/api.txt. If this is not
> what program does it is a bug. What userspace you see the problem with?

You're right, this patch should not be necessary.