Re: Problems in PV dom0 on recent x86 hardware

["Roger Pau Monné" <roger.pau@citrix.com>]

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?

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.

Roger.