On Mon, May 18, 2009 at 03:33:20PM +0300, Avi Kivity wrote: > Michael S. Tsirkin wrote: >>> >>>> On the other hand, in MSI-X mask bit is mandatory, not optional >>>> so we'll have to support it for assigned devices at some point. >>>> >>>> If we are worried about speed of masking/unmasking MSI-X interrupts for >>>> assigned devices (older kernels used to mask them, recent kernels leave >>>> this to drivers) we will probably need to have MSI-X support in the >>>> kernel, and have kernel examine the mask bit before injecting the >>>> interrupt, just like real devices do. >>>> >>> Yes. >>> >> >> Actually, if we do that, we'll need to address a race where a driver >> has updated the mask bit in the window after we tested it >> and before we inject the interrupt. Not sure how to do this. >> > > The driver can't tell if the interrupt came first, so it's a valid race > (real hardware has the same race). The driver for real device can do a read followed by sync_irq to flush out interrupts. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
