I don't recall seeing a followup to this post.
To put Michael's second suggestion into patch form, the following fixes
the problem for me:
--- kvm-81.orig/qemu/qemu-char.c 2008-12-14 06:16:27.000000000 -0700
+++ kvm-81/qemu/qemu-char.c 2009-02-02 14:12:20.000000000 -0700
@@ -1078,20 +1078,21 @@
if (sarg | TIOCM_DTR)
*targ |= CHR_TIOCM_DTR;
if (sarg | TIOCM_RTS)
*targ |= CHR_TIOCM_RTS;
}
break;
case CHR_IOCTL_SERIAL_SET_TIOCM:
{
int sarg = *(int *)arg;
int targ = 0;
+ ioctl(s->fd_in, TIOCMGET, &targ);
if (sarg | CHR_TIOCM_DTR)
targ |= TIOCM_DTR;
if (sarg | CHR_TIOCM_RTS)
targ |= TIOCM_RTS;
ioctl(s->fd_in, TIOCMSET, &targ);
}
break;
default:
return -ENOTSUP;
}
Is this approach palatable to folks?
david
Michael Tokarev wrote:
> Michael Tokarev ?????:
>> After some debugging and debugging, with a help
>> Hollis Blanchard on #kvm@freenode, I discovered
>> that kvm (or, rather, qemu) does not work correctly
>> with serial ports, at least on linux. One problem
>> report has already here, author Cc'd -- see e.g.
>> http://marc.info/?l=kvm&m=122995568009533&w=2 .
>>
>> Here's what's going on.
>>
>> When opening a host's port, kvm resets the status
>> lines, doing this:
>>
>> ioctl(13, TIOCMGET, [TIOCM_DTR|TIOCM_RTS|TIOCM_CTS|TIOCM_DSR|0x4000])
>> ioctl(13, TIOCMSET, [TIOCM_DTR|TIOCM_RTS])
>>
>> which results in the following set
>>
>> ioctl(13, TIOCMGET, [TIOCM_DTR|TIOCM_RTS|TIOCM_CTS|TIOCM_DSR])
>
> Here's the possible solution (NotAPAtch(tm)):
>
> In kvm-xx/qemu/qemu-char.c:
>
> case CHR_IOCTL_SERIAL_SET_TIOCM:
> {
> int sarg = *(int *)arg;
> int targ = 0; <==== change this 0 to 0x4000
> if (sarg | CHR_TIOCM_DTR)
> targ |= TIOCM_DTR;
> if (sarg | CHR_TIOCM_RTS)
> targ |= TIOCM_RTS;
> ioctl(s->fd_in, TIOCMSET, &targ);
> }
> break;
>
> This is obviously a hack, esp. since this bit is not
> always present even on linux (after reading 8250.c
> driver).
>
> Real fix will be, I guess, to read the full set
> first, and combine it with DTR|RTS received from
> guest, something like this:
>
> case
> {
> int sarg = *(int *)arg;
> int targ = 0;
> ioctl(s->fd_in, TIOCMGET, &targ);
> if (!(sarg | CHR_TIOCM_DTR))
> targ &= ~TIOCM_DTR;
> if (!(sarg | CHR_TIOCM_RTS))
> targ ~= ~TIOCM_RTS;
> ioctl(s->fd_in, TIOCMSET, &targ);
> }
> break;
>
> I.e., to always keep all the other bits, but
> allow changing DTR and RTS.
>
> Again, I don't know how it's linux-specific, but
> it seems the solution above should work on other
> platforms just fine.
>
> /mjt
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