>>> On 22.05.13 at 00:41, Konrad Rzeszutek Wilk <konrad.w...@oracle.com> wrote: > On Tue, May 21, 2013 at 10:50:09PM +0100, Stefano Stabellini wrote: >> We have to be careful about this: the point of PHYSDEVOP_get_free_pirq is >> that Linux can know for sure the pirq that is going to be used to map the >> MSI by QEMU. If you modify is_free_pirq that way, suddenly the pirq >> could be allocated for something else after Linux called >> PHYSDEVOP_get_free_pirq and before QEMU called xc_physdev_map_pirq_msi. > > Yes. And I think the 'is_free_pirq' modification above is incorrect. > > I think the fix should be in the unmap_pirq code (hypervisor) to check > if the arch.irq is either zero or PIRQ_ALLOCATED. Right now it only > checks for zero.
Which check are you talking about? Looking at physdev_unmap_pirq() I see none at all, unmap_domain_pirq() has a <= 0 check, and unmap_domain_pirq_emuirq() again doesn't appear to have any. If you're talking about unmap_domain_pirq(), then you'll need to be careful: A negative value here doesn't necessarily mean PIRQ_ALLOCATED, but could also come from another run that found it necessary to force the unbind. Hence the definition of PIRQ_ALLOCATED would then collide with the (unlikely?) case of IRQ1 having got assigned to a guest. To be on the safe side, we should therefore redefine PIRQ_ALLOCATED to say INT_MIN. Jan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
