[Libvir] Re: [PATCH 2/7] Fix issues with QEMU monitor interface.

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.