On Mon, Aug 13, 2007 at 05:59:15AM -0400, Daniel Veillard wrote:
> On Sun, Aug 12, 2007 at 07:11:34PM -0400, Jim Paris wrote:
> > Due to the TTY layer, sending "\n" to the qemu monitor translates
> > into "\r\n" when received. This triggers a bug in older versions of
> > QEMU (KVM <= 33) because the same command is executed twice, and
> > still has problems with fixed QEMU because the "(qemu)" prompt is
> > printed twice. Switch all monitor commands to end with "\r" which
> > avoids both issues.
> >
> > The QEMU monitor sends frequent terminal escape sequences, typically
> > \033[D and \033[K. At times, these interfere with the prompt
> > detection when they get sent between "\n" and "(qemu) ". Fix the
> > issue by filtering out these sequences when they are received.
>
> I think DanP can better comment on the QEmu interaction than me,
> but the patch looks simple and clean except:
It looks sane to me - I had no idea QEMU was sending this escape sequences.
>
> > @@ -1333,14 +1335,23 @@ static int qemudMonitorCommand(struct qemud_driver *driver ATTRIBUTE_UNUSED,
> > return -1;
> > }
> > buf = b;
> > - memmove(buf+size, data, got);
> > - buf[size+got] = '\0';
> > - size += got;
> > +
> > + /* Copy data, skipping 3-byte escape sequences */
> > + for (i = 0; i < got; i++) {
> > + if (data[i] == '\033')
> > + skip = 3;
> > + if (skip)
> > + skip--;
> > + else
> > + buf[size++] = data[i];
> > + }
> > + buf[size] = '\0';
> > }
>
> It seems that if for some reason you do a partial read on the QEmu
> console descriptor ending in the middle of the escape command you may
> have a problem. But it's possible that the way reads are done, and input
> is chunked garantees that this won't happen, DanP can probably confirm
> it's just fine :-)
We're reading from a Psuedo-TTY which is line buffered, so I think the OS
should guarentee that we can read a whole lines worth of data without
getting EAGAIN.
Dan.
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