lkml.org 
[lkml]   [2008]   [Aug]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectSerial of guest kernel complain "too much work" in kvm/qemu
Date
From

Hi all,

How is this going?
http://www.archivum.info/qemu-devel@nongnu.org/2008-02/msg00169.html

I use serial as guest's default stdio on powerpc platform.
When displaying a number of characters, e.g. cat a big ascii file,
the serial always hangs as it encounters overwhelming interrupts,
and then complains "serial8250: too much work for irq 42".

The problem is that:
serial in qemu generate an interrupt on every output character,
while Linux driver reads serial data in a loop but gives up after a fixed number (256) of iterations.
So if serial output more than 256 characters in a short time, the serial die.

I had to use the patch below to get it worked around.

So what is the best way to solve it?

---
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c index be95e55..af3e569 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -70,7 +70,7 @@ static unsigned int nr_uarts = CONFIG_SERIAL_8250_RUNTIME_UARTS;
#define DEBUG_INTR(fmt...) do { } while (0)
#endif

-#define PASS_LIMIT 256
+#define PASS_LIMIT 65536

/*
* We default to IRQ0 for the "no irq" hack. Some
\
 
 \ /
  Last update: 2008-08-21 08:07    [W:1.373 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site