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[Xen-devel] Re: [Xen-staging] [xen-unstable] [QEMU-DM] Upgrade emulated

To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: [Xen-devel] Re: [Xen-staging] [xen-unstable] [QEMU-DM] Upgrade emulated UART to 16550A.
From: "Trolle Selander" <trolle.selander@xxxxxxxxx>
Date: Fri, 7 Dec 2007 18:51:42 +0100
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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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