[Xen-devel] Re: [Xen-staging] [xen-unstable] [QEMU-DM] Upgrade emulated UART to 16550A.

["Trolle Selander" <trolle.selander@xxxxxxxxx>]

I'll look into it further, though I'm a bit puzzled as to why it was
faster before - the old code would attempt to retransmit every 100ms,
for up to 300ms. That's a LOT longer than my code will retry at any
kind of sane baud-rates. What guest are you running in the HVM? 
At one point I was considering adding a "backend type" field for
the qemu char devices to prevent having to detect if the backend device
was a physical port from within serial.c. Perhaps I'll need to go back
to that plan and treat pty's differently, or simply skip the transmit
retries entirely when the backend isn't a physical serial port.

On Dec 7, 2007 6:21 PM, Alex Williamson <alex.williamson@xxxxxx> wrote:

On Wed, 2007-12-05 at 23:07 +0100, Trolle Selander wrote:
> This patch fixes the issue. It also changes the name of an
> inappropriately named timer.

Hi Trolle,

 Yes, with this patch, my HVM domain will eventually boot.
Unfortunately it takes 2 minutes now to get through all the UART
timeouts and get to the firmware menu.  Prior to the new 16550A UART
driver, it took 10 seconds.  I think we need to do something smarter
than drop characters after some number of timeouts.  We're doomed to
terrible slowness anytime the console is disconnected that way.  Thanks,

       Alex

--
Alex Williamson                             HP Open Source & Linux Org.

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