On 14/11/14 15:54, Jiang Liu wrote: > On 2014/11/14 5:28, Marc Zyngier wrote: >> On 13/11/14 21:11, Thomas Gleixner wrote: >>> On Thu, 13 Nov 2014, Marc Zyngier wrote: >>>> With the new stacked irq domains, it becomes pretty tempting >>>> to allocate an MSI domain per PCI bus, which would remove >>>> the requirement of either relying on arch-specific code, or >>>> a default PCI MSI domain. >>> >>> Right. That's what I roughly had in mind. And that would solve the >>> multi-iommu issue on x86 nicely as well. We establish the association >>> at the time where the bus gets populated. So the whole lookup magic >>> simply goes away. >> >> Great. I've pushed the whole thing out with this patch, the couple >> of fixes I mentioned earlier, as well as the whole ITS code: >> >> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git irq/stacked-its-v2 > Hi Marc, > I have looked at the code, and found some issues. > 1) With my next version, no need to implemeent its_pci_msi_free() > anymore. msi_domain_free_irqs() will reset desc->irq to zero > for all architectures. Great. The less code, the better. > 2) This piece of code in its_msi_prepare() may run into trouble > for PCI device with both MSI and MSIX capability. I will change > msi_prepare() prototype to pass in the "nvec" parameter. And you > may access first_pci_msi_entry()->msi_attrib.is_msix to get > allocation type if needed. > nvec = pci_msix_vec_count(pdev); > if (nvec < 0) > nvec = pci_msi_vec_count(pdev); > if (nvec < 0) > return nvec; Ah, good point. Having nvec will make things simpler indeed. I have the feeling that the ITS driver may not be the only one to require such a thing. > 3) Do we need to increase the default of NUM_MSI_ALLOC_SCRATCHPAD_REGS > to 4? 2 is a little too limited. I'd say that 2 is enough for now. The ITS only uses one (the second one is for debug only). Should the need arise, we can bump it up later. Thanks, M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
