This is actually not an ARM specific question, so changing the subject and CC'ing more people.
On Wed, 14 Dec 2016, Konrad Rzeszutek Wilk wrote: > On Tue, Dec 13, 2016 at 07:14:27PM -0600, Jiandi An wrote: > > Hi Guys, > > > > Xen currently does not handle mapping of MMIO regions specified under > > OperationRegion in ACPI ASL. OperationRegion is well defined in ACPI > > specification. I'm seeking for architectural direction on adding support > > for mapping OperationRegion. > > > > Some context here. Mapping of resources specificed under _CRS in ACPI is > > handled by dom0 requesting Xen to map as platform devices are added. > > https://lwn.net/Articles/674666/ provided service xen_map_device_mmio() in > > dom0 to call Xen to map and it's done so by registering > > xen_platform_notifier() platform bus driver. This covers the platform > > devices. > > > > The OperationRegion access in dom0 is in acpica path. The following is a > > stack of the code path where OperationRegion is parsed. > > acpi_ex_system_memory_space_handler() gets the parsed address specified in > > OperationRegion in ACPI and maps it then performs the memory read or write. > > > > > > acpi_ex_system_memory_space_handler+0x378/0x424 > > acpi_ev_address_space_dispatch+0x294/0x310 > > acpi_ex_access_region+0x3c0/0x468 > > acpi_ex_field_datum_io+0x14c/0x380 > > acpi_ex_extract_from_field+0xe8/0x2f4 > > acpi_ex_read_data_from_field+0x330/0x38c > > acpi_ex_resolve_node_to_value+0x310/0x3fc > > acpi_ex_resolve_to_value+0x354/0x3e8 > > acpi_ds_evaluate_name_path+0xa4/0x15c > > acpi_ds_exec_end_op+0xbc/0x6c8 > > acpi_ps_parse_loop+0x7ac/0x840 > > acpi_ps_parse_aml+0x1c4/0x434 > > acpi_ps_execute_method+0x1f0/0x2a0 > > acpi_ns_evaluate+0x2e4/0x424 > > acpi_ut_evaluate_object+0xb0/0x250 > > acpi_ut_execute_STA+0xb0/0x164 > > acpi_ns_init_one_device+0xac/0x250 > > acpi_ns_walk_namespace+0x108/0x254 > > acpi_ns_initialize_devices+0x274/0x35c > > acpi_initialize_objects+0x90/0xf0 > > acpi_init+0xc0/0x30c > > do_one_initcall+0x44/0x138 > > kernel_init_freeable+0x148/0x1ec > > kernel_init+0x18/0x108 > > > > The workaround in testing for handling OperationRegion I did is to call > > xen_map_device_mmio() to map the resource specificied in OperationRegion if > > it's dom0 running under XEN in acpi_ex_system_memory_space_handler(). But > > this is a fairly generic ACPI code path. Looking for achitectural > > suggestion to properly handle OperationRegion for Xen on ARM. > > The ACPI code path obviously calls the underlaying OS code to map it. > Could this path have an wrapper around it (so one could register > different underlaying 'map_device_mmio' function calls)? > _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
