Hi Bjorn, On Wed, Apr 17, 2024 at 09:03:13PM +0530, Sunil V L wrote: <snip> > > I think fundamentally there are two issues here. > > 1) MSI domain should have been setup properly when > pci_register_host_bridge() is called. I see that pci_arch_init() which > is supposed to get called early calls x86_create_pci_msi_domain(). > pci_register_host_bridge() also calls pci_set_bus_msi_domain() to setup > the MSI domain which can walk up to host bridge to find. So, not sure > why PCI_BUS_FLAGS_NO_MSI is getting set. Is there an issue in walking up > the tree? > I think I understand now why this is happening on X86. In X86, even though x86_create_pci_msi_domain() sets up the MSI domain, it never informs IRQ framework. Only later in pcibios_device_add(), the device's MSI domain will be set which is too late for this bridge logic. So, when pci_set_bus_msi_domain() is called from pci_register_host_bridge(), it will not get it. It works in RISC-V (I guess ARM64 as well) because, the irqchip driver for MSI controller registers using pci_msi_register_fwnode_provider(). But, if we set bridge->msi_domain = true in X86, it will disable MSI even though it supports MSI which is really bad. Please correct me if I am wrong with the analysis. If correct, what do you think the way forward if using CONFIG option is not good? I tried to register the domain in below commit but I don't feel it is a cleaner way. https://github.com/vlsunil/linux/commit/d6cf76f10c225c94fffb286b7a3e803a4e37df54 Thanks, Sunil
