RE: [Xen-devel] [PATCH] x86: change IO-APIC ack method default for single IO-APIC systems

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

xen-devel-bounces@xxxxxxxxxxxxxxxxxxx <> wrote:
> Ever since 3.0.2 we've been carrying this patch in our products. Since
> there was no indication that there would be anything wrong with the
> 'new' IO-APIC ack method added back then, we finally decided to drop
> this patch recently from SLE11, to find that the subsequent release
> candidate failed to work on at least on system without using

This is a bit strange, a bit curios that do you know the reason that it not 
working? 

> "ioapic_ack=old". With that knowledge I think it is now reasonable to
> include that patch in -unstable, as the introduction of the 'new' ack
> method was only to address issues with certain chipsets silently
> setting up alternative IRQ routes when RTEs in secondary IO-APICs got
> masked. 
> 
> Here some data on the hardware the issue was reportedly found on:
> * intel DQ965CO motherboard (i82Q965 chipset)
> * intel 82566DM NIC
> * intel ICH8R (82801H)
> * Marvell 88SE6101 IDE controller
> * nVidia 8600GT graphics
> * intel Q6600 CPU
> * 8GB RAM
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
> 
> --- 2009-01-08.orig/xen/arch/x86/io_apic.c    2009-01-09 12:43:35.000000000
> +0100 +++ 2009-01-08/xen/arch/x86/io_apic.c   2009-01-21
> 14:11:53.000000000 +0100
> @@ -1352,7 +1352,7 @@ static unsigned int startup_level_ioapic
>     return 0; /* don't check for pending */
> }
> 
> -int ioapic_ack_new = 1;
> +int ioapic_ack_new = -1;
> static void setup_ioapic_ack(char *s)
> {
>     if ( !strcmp(s, "old") )
> @@ -1839,6 +1839,8 @@ void __init setup_IO_APIC(void)     else
>         io_apic_irqs = ~PIC_IRQS;
> 
> +    if (ioapic_ack_new < 0)
> +        ioapic_ack_new = (nr_ioapics > 1);
>     printk("ENABLING IO-APIC IRQs\n");
>     printk(" -> Using %s ACK method\n", ioapic_ack_new ? "new" : "old");
> 
> 
> 
> 
> 
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