Messages in this thread Patch in this message | | | Subject | Serial of guest kernel complain "too much work" in kvm/qemu | Date | Thu, 21 Aug 2008 14:03:56 +0800 | From | "Liu Yu" <> |
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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
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