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From: "Pavel Dovgalyuk" <dovgaluk@ispras.ru>
References: <20170124071654.4572.41407.stgit@PASHA-ISP>
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Date: Wed, 25 Jan 2017 14:12:57 +0300
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Subject: Re: [Qemu-devel] [PATCH v7 03/14] replay: exception replay fix
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To: 'Paolo Bonzini' <pbonzini@redhat.com>, 'Pavel Dovgalyuk' <pavel.dovgaluk@ispras.ru>, qemu-devel@nongnu.org
Cc: kwolf@redhat.com, peter.maydell@linaro.org, mst@redhat.com, jasowang@redhat.com, quintela@redhat.com, kraxel@redhat.com

> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> On 24/01/2017 08:17, Pavel Dovgalyuk wrote:
> > @@ -451,6 +451,10 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
> >  #ifndef CONFIG_USER_ONLY
> >      } else if (replay_has_exception()
> >                 && cpu->icount_decr.u16.low + cpu->icount_extra == 0) {
> > +        /* Break the execution loop in case of running out of TB cache.
> > +           This is needed to make flushing of the TB cache, because
> > +           real flush is queued to be executed outside the cpu loop. */
> > +        cpu->exception_index = EXCP_INTERRUPT;
> >          /* try to cause an exception pending in the log */
> >          cpu_exec_nocache(cpu, 1, tb_find(cpu, NULL, 0), true);
> >          *ret = -1;
> 
> Why is replay_has_exception() related to be running out of TB cache?

It doesn't.
Calling tb_find when there is not space in cache causes tb_flush and cpu_loop_exit.
But execution loop will continue, because there is no reason to break it
(like setting exception_index).

Pavel Dovgalyuk