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Re: [Qemu-devel] what is the behavier precisely if a tb was interrupted

From: Peter Maydell
Subject: Re: [Qemu-devel] what is the behavier precisely if a tb was interrupted by a interrupt or signal?
Date: Mon, 24 Dec 2018 13:49:07 +0000

On Mon, 24 Dec 2018 at 10:11, tugouxp <address@hidden> wrote:
>  think about the scenario like that, a tb block contain  9 native 
> instructions  execute sequentially
>  if a interrupt or a signal happens  before instruction 6 executed,  did the 
> tb  be finished before response to the interrupt  or
> the  exited at once to response the interrupt?

We don't check in the middle of a TB for conditions like
interrupts. The only thing that can cause a TB to stop
execution halfway through is if it does something that
provokes a synchronous exception (for instance, if it
does a guest memory access that triggers a guest CPU
page fault, or if it emulates a guest instruction that
is required to trap). Those we emulate by longjumping out
from the generated code to the top level loop.
Asynchronous events like emulated interrupts we only
check at the beginning of the TB: we emit code which
tests a flag and returns early.

-- PMM

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