Re: Problems in PV dom0 on recent x86 hardware

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.07.2024 11:08, Roger Pau Monné wrote:
> On Mon, Jul 08, 2024 at 10:37:22AM +0200, Jan Beulich wrote:
>> On 08.07.2024 10:15, Jürgen Groß wrote:
>>> I've got an internal report about failures in dom0 when booting with
>>> Xen on a Thinkpad P14s Gen 3 AMD (kernel 6.9).
>>>
>>> With some debugging I've found that the UCSI driver seems to fail to
>>> map MFN feec2 as iomem, as the hypervisor is denying this mapping due
>>> to being part of the MSI space. The mapping attempt seems to be the
>>> result of an ACPI call of the UCSI driver:
>>>
>>> [   44.575345] RIP: e030:xen_mc_flush+0x1e8/0x2b0
>>> [   44.575418]  xen_leave_lazy_mmu+0x15/0x60
>>> [   44.575425]  vmap_range_noflush+0x408/0x6f0
>>> [   44.575438]  __ioremap_caller+0x20d/0x350
>>> [   44.575450]  acpi_os_map_iomem+0x1a3/0x1c0
>>> [   44.575454]  acpi_ex_system_memory_space_handler+0x229/0x3f0
>>> [   44.575464]  acpi_ev_address_space_dispatch+0x17e/0x4c0
>>> [   44.575474]  acpi_ex_access_region+0x28a/0x510
>>> [   44.575479]  acpi_ex_field_datum_io+0x95/0x5c0
>>> [   44.575482]  acpi_ex_extract_from_field+0x36b/0x4e0
>>> [   44.575490]  acpi_ex_read_data_from_field+0xcb/0x430
>>> [   44.575493]  acpi_ex_resolve_node_to_value+0x2e0/0x530
>>> [   44.575496]  acpi_ex_resolve_to_value+0x1e7/0x550
>>> [   44.575499]  acpi_ds_evaluate_name_path+0x107/0x170
>>> [   44.575505]  acpi_ds_exec_end_op+0x392/0x860
>>> [   44.575508]  acpi_ps_parse_loop+0x268/0xa30
>>> [   44.575515]  acpi_ps_parse_aml+0x221/0x5e0
>>> [   44.575518]  acpi_ps_execute_method+0x171/0x3e0
>>> [   44.575522]  acpi_ns_evaluate+0x174/0x5d0
>>> [   44.575525]  acpi_evaluate_object+0x167/0x440
>>> [   44.575529]  acpi_evaluate_dsm+0xb6/0x130
>>> [   44.575541]  ucsi_acpi_dsm+0x53/0x80
>>> [   44.575546]  ucsi_acpi_read+0x2e/0x60
>>> [   44.575550]  ucsi_register+0x24/0xa0
>>> [   44.575555]  ucsi_acpi_probe+0x162/0x1e3
>>> [   44.575559]  platform_probe+0x48/0x90
>>> [   44.575567]  really_probe+0xde/0x340
>>> [   44.575579]  __driver_probe_device+0x78/0x110
>>> [   44.575581]  driver_probe_device+0x1f/0x90
>>> [   44.575584]  __driver_attach+0xd2/0x1c0
>>> [   44.575587]  bus_for_each_dev+0x77/0xc0
>>> [   44.575590]  bus_add_driver+0x112/0x1f0
>>> [   44.575593]  driver_register+0x72/0xd0
>>> [   44.575600]  do_one_initcall+0x48/0x300
>>> [   44.575607]  do_init_module+0x60/0x220
>>> [   44.575615]  __do_sys_init_module+0x17f/0x1b0
>>> [   44.575623]  do_syscall_64+0x82/0x170
>>> [   44.575685] 1 of 1 multicall(s) failed: cpu 4
>>> [   44.575695]   call  1: op=1 result=-1 
>>> caller=xen_extend_mmu_update+0x4e/0xd0 
>>> pars=ffff888267e25ad0 1 0 7ff0 args=9ba37a678 80000000feec2073
>>>
>>> The pte value of the mmu_update call is 80000000feec2073, which is rejected 
>>> by
>>> the hypervisor with -EPERM.
>>>
>>> Before diving deep into the UCSI internals, is it possible that the 
>>> hypervisor
>>> needs some update (IOW: could it be the mapping attempt should rather be
>>> honored, as there might be an I/O resources at this position which dom0 
>>> needs
>>> to access for using the related hardware?)
>>
>> Adding to Andrew's reply: Is there any BAR in the system covering that 
>> address?
>> Or is it rather ACPI "making up" that address (which would remind me of 
>> IO-APIC
>> space being accessed by certain incarnations of ACPI, resulting in similar
>> issues)?
> 
> So you think ACPI is using some kind of backdoor to access the local
> APIC registers?

No, I'm wondering if they're trying to access *something*. As it stands we
don't even know what kind of access is intended; all we know is that they're
trying to map that page (and maybe adjacent ones).

> It's my understanding the local APIC registers are all located in the
> first page of the range (0xfee00).  It would also be weird because
> ACPI doesn't know whether the APIC is in x2APIC mode.

Indeed.

Jan