On 08/09/2019 19:28, Boris Ostrovsky wrote: > On 9/6/19 7:00 PM, Igor Druzhinin wrote: >> >> On 06/09/2019 23:30, Boris Ostrovsky wrote: >>> >>> Where is MCFG parsed? pci_arch_init()? >>>> It happens twice: >> 1) first time early one in pci_arch_init() that is arch_initcall - that >> time pci_mmcfg_list will be freed immediately there because MCFG area is >> not reserved in E820; >> 2) second time late one in acpi_init() which is subsystem_initcall right >> before where PCI enumeration starts - this time ACPI tables will be >> checked for a reserved resource and pci_mmcfg_list will be finally >> populated. >> >> The problem is that on a system that doesn't have MCFG area reserved in >> E820 pci_mmcfg_list is empty before acpi_init() and our PCI hooks are >> called in the same place. So MCFG is still not in use by Xen at this >> point since we haven't reached our xen_mcfg_late(). > > > Would it be possible for us to parse MCFG ourselves in pci_xen_init()? I > realize that we'd be doing this twice (or maybe even three times since > apparently both pci_arch_init() and acpi_ini() do it). >
I don't thine it makes sense: a) it needs to be done after ACPI is initialized since we need to parse it to figure out the exact reserved region - that's why it's currently done in acpi_init() (see commit message for the reasons why) b) given (a) we cannot do it ourselves before acpi_init and after is too late as we're already past ACPI PCI enumeration c) we'd have to do it in the same place I call xen_mcfg_late() and it'd be code duplication of what's already done by the existing code. Igor
