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i8257: rewrite DMA_schedule to avoid hooking into the CPU loop

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The i8257 DMA controller uses an idle bottom half, which by default
does not cause the main loop to exit.  Therefore, the DMA_schedule
function is there to ensure that the CPU relinquishes the iothread
mutex to the iothread.

However, this is not enough since the iothread will call
aio_compute_timeout() and go to sleep again.  In the iothread
world, forcing execution of the idle bottom half is much simpler,
and only requires a call to qemu_notify_event().  Do it, removing
the need for the "cpu_request_exit" pseudo-irq.  The next patch
will remove it.

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2015-02-16 14:08:22 +01:00
parent 5f5b5942d5
commit 19d2b5e6ff
5 changed files with 16 additions and 10 deletions
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2
hw/sparc/sun4m.c
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@ -109,7 +109,7 @@ int DMA_write_memory (int nchan, void *buf, int pos, int size)
}
void DMA_hold_DREQ (int nchan) {}
void DMA_release_DREQ (int nchan) {}
void DMA_schedule(int nchan) {}
void DMA_schedule(void) {}
void DMA_init(int high_page_enable, qemu_irq *cpu_request_exit)
{