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Date: Fri, 7 Jan 2011 18:53:59 +0200
From: Gleb Natapov <gleb@redhat.com>
Message-ID: <20110107165359.GA10205@redhat.com>
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Subject: [Qemu-devel] Re: qemu-kvm vs. qemu: Terminate cpu loop on reset?
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To: Jan Kiszka <jan.kiszka@web.de>
Cc: qemu-devel <qemu-devel@nongnu.org>, kvm <kvm@vger.kernel.org>

On Fri, Jan 07, 2011 at 04:57:31PM +0100, Jan Kiszka wrote:
> Hi,
> 
> does anyone immediately know if this hunk from vl.c
> 
> @@ -1278,6 +1197,10 @@ void qemu_system_reset_request(void)
>      } else {
>          reset_requested = 1;
>      }
> +    if (cpu_single_env) {
> +        cpu_single_env->stopped = 1;
> +        cpu_exit(cpu_single_env);
> +    }
>      qemu_notify_event();
>  }
> 
> is (semantically) relevant for upstream as well? IIUC, it ensures that
> the kvm cpu loop is not continued if an IO access called into
> qemu_system_reset_request.
> 
I don't know TCG enough to tell. If TCG can continue vcpu execution
after io without checking reset_requested then it is relevant for
upstream too.

> If yes, then it would be a good time to push a patch: these bits will
> fall to dust on next merge from upstream (vl.c no longer has access to
> the cpu state).
> 
On a next merge cpu state will have to be exposed to vl.c then. This
code cannot be dropped in qemu-kvm.

--
			Gleb.