Re: [Qemu-devel] [PATCH 7/7] ahci: work around bug with level interrupts

[Alexander Graf]

On 01.02.2011, at 17:34, Aurelien Jarno wrote:

> On Tue, Feb 01, 2011 at 03:51:32PM +0100, Alexander Graf wrote:
>> When using level based interrupts, the interrupt is treated the same as an
>> edge triggered one: leaving the line up does not retrigger the interrupt.
>> 
>> In fact, when not lowering the line, we won't ever get a new interrupt inside
>> the guest. So let's always retrigger an interrupt as soon as the OS ack'ed
>> something on the device. This way we're sure the guest doesn't starve on
>> interrupts until someone fixes the actual interrupt path.
> 
> Given this issue mostly concerns x86 and not other architectures where
> the SATA emulation can probably be used, what about putting the two
> versions of the codes like in i8259.c:
> 
> | * all targets should do this rather than acking the IRQ in the cpu */
> | #if defined(TARGET_MIPS) || defined(TARGET_PPC) || defined(TARGET_ALPHA)
> 
> The list of architectures here is reduced given the few architectures 
> that actually use the i8259, so for ahci.c it should probably be #if not
> defined(TARGET_I386) instead.

Because then we'd have to build the ahci code conditionally on the 
architecture. Right now it builds into libhw :)


Alex