Re: [Qemu-devel] Re: 2.6.24 says "serial8250: too much work for irq4" a lot.

["Blue Swirl" <blauwirbel@gmail.com>]

On 2/9/08, H. Peter Anvin <hpa@zytor.com> wrote:
> Blue Swirl wrote:
> >>
> >> If you look at the patch, there are no timing dependencies; the only
> >> parameter is the depth of the virtual queue.  The exhaustion is
> >> completely controlled by target OS access patterns.
> >
> > Thanks, this clarified the difference. But I'll rephrase my original comment:
> >
> > The patch looks OK, but the simulated FIFO exhaustion should benefit
> > all devices, as
> > discussed here:
> > http://lists.gnu.org/archive/html/qemu-devel/2007-12/msg00283.html
>
> The difference is you *can't* do that in a general layer.

What makes you think that is impossible? Just move the
serial_clear_burst to vl.c under name chr_clear_burst, move burst_len
to CharDriverState and introduce a new function in vl.c that contains
the burst length check. This is functionally identical to your patch.
For 100% compatibility, the init functions could be changed so that
only PC serial is affected, but I think all character devices would
benefit from this.

Also win2k install hack in ide.c seems to be related to this problem,
so even more generic solution would be desirable.