[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH for-4.20?] x86/dom0: be less restrictive with the Interrupt Address Range
On Wed, Feb 12, 2025 at 04:38:00PM +0100, Roger Pau Monne wrote: > Xen currently prevents dom0 from creating CPU or IOMMU page-table mappings > into the interrupt address range [0xfee00000, 0xfeefffff]. This range has > two different purposes. For accesses from the CPU is contains the default > position of local APIC page at 0xfee00000. For accesses from devices > it's the MSI address range, so the address field in the MSI entries > (usually) point to an address on that range to trigger an interrupt. > > There are reports of Lenovo Thinkpad devices placing what seems to be the > UCSI shared mailbox at address 0xfeec2000 in the interrupt address range. > Attempting to use that device with a Linux PV dom0 leads to an error when > Linux kernel maps 0xfeec2000: > > RIP: e030:xen_mc_flush+0x1e8/0x2b0 > xen_leave_lazy_mmu+0x15/0x60 > vmap_range_noflush+0x408/0x6f0 > __ioremap_caller+0x20d/0x350 > acpi_os_map_iomem+0x1a3/0x1c0 > acpi_ex_system_memory_space_handler+0x229/0x3f0 > acpi_ev_address_space_dispatch+0x17e/0x4c0 > acpi_ex_access_region+0x28a/0x510 > acpi_ex_field_datum_io+0x95/0x5c0 > acpi_ex_extract_from_field+0x36b/0x4e0 > acpi_ex_read_data_from_field+0xcb/0x430 > acpi_ex_resolve_node_to_value+0x2e0/0x530 > acpi_ex_resolve_to_value+0x1e7/0x550 > acpi_ds_evaluate_name_path+0x107/0x170 > acpi_ds_exec_end_op+0x392/0x860 > acpi_ps_parse_loop+0x268/0xa30 > acpi_ps_parse_aml+0x221/0x5e0 > acpi_ps_execute_method+0x171/0x3e0 > acpi_ns_evaluate+0x174/0x5d0 > acpi_evaluate_object+0x167/0x440 > acpi_evaluate_dsm+0xb6/0x130 > ucsi_acpi_dsm+0x53/0x80 > ucsi_acpi_read+0x2e/0x60 > ucsi_register+0x24/0xa0 > ucsi_acpi_probe+0x162/0x1e3 > platform_probe+0x48/0x90 > really_probe+0xde/0x340 > __driver_probe_device+0x78/0x110 > driver_probe_device+0x1f/0x90 > __driver_attach+0xd2/0x1c0 > bus_for_each_dev+0x77/0xc0 > bus_add_driver+0x112/0x1f0 > driver_register+0x72/0xd0 > do_one_initcall+0x48/0x300 > do_init_module+0x60/0x220 > __do_sys_init_module+0x17f/0x1b0 > do_syscall_64+0x82/0x170 > > Remove the restrictions to create mappings the interrupt address range for > dom0. Note that the restriction to map the local APIC page is enforced > separately, and that continues to be present. > > For PVH dom0 it's important that the restriction is removed from > arch_iommu_hwdom_init(), as the logic in that function creates mappings in > both the CPU and the IOMMU page tables for reserved regions in the memory > map. The expectation is that the page at 0xfeec2000 will be added to the > host memory map using the EfiACPIMemoryNVS type, so arch_iommu_hwdom_init() > will create a mapping for it. > > Note that even if the interrupt address range entries are populated in the > IOMMU page-tables no device access will reach those pages. Device accesses > to the Interrupt Address Range will always be converted into Interrupt > Messages and are not subject to DMA remapping. > > There's also the following restriction noted in Intel VT-d: > > > Software must not program paging-structure entries to remap any address to > > the interrupt address range. Untranslated requests and translation requests > > that result in an address in the interrupt range will be blocked with > > condition code LGN.4 or SGN.8. Translated requests with an address in the > > interrupt address range are treated as Unsupported Request (UR). > > However this restriction doesn't apply to the identity mappings possibly > created for dom0, since the interrupt address range is never subject to DMA > remapping. > > Reported-by: Jürgen Groß <jgross@xxxxxxxx> > Link: > https://lore.kernel.org/xen-devel/baade0a7-e204-4743-bda1-282df74e5f89@xxxxxxxx/ > Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx> > --- > xen/arch/x86/dom0_build.c | 4 ---- > xen/drivers/passthrough/x86/iommu.c | 5 ----- > 2 files changed, 9 deletions(-) > > diff --git a/xen/arch/x86/dom0_build.c b/xen/arch/x86/dom0_build.c > index e8f5bf5447bc..d1b4ef83b2d0 100644 > --- a/xen/arch/x86/dom0_build.c > +++ b/xen/arch/x86/dom0_build.c > @@ -555,10 +555,6 @@ int __init dom0_setup_permissions(struct domain *d) > if ( !rangeset_contains_singleton(mmio_ro_ranges, mfn) ) > rc |= iomem_deny_access(d, mfn, mfn); > } > - /* MSI range. */ > - rc |= iomem_deny_access(d, paddr_to_pfn(MSI_ADDR_BASE_LO), > - paddr_to_pfn(MSI_ADDR_BASE_LO + > - MSI_ADDR_DEST_ID_MASK)); > /* HyperTransport range. */ > if ( boot_cpu_data.x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON) ) > { > diff --git a/xen/drivers/passthrough/x86/iommu.c > b/xen/drivers/passthrough/x86/iommu.c > index 8b1e0596b84a..ec17701c90dd 100644 > --- a/xen/drivers/passthrough/x86/iommu.c > +++ b/xen/drivers/passthrough/x86/iommu.c > @@ -475,11 +475,6 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain *d) > if ( rc ) > panic("IOMMU failed to remove Xen ranges: %d\n", rc); > > - /* Remove any overlap with the Interrupt Address Range. */ > - rc = rangeset_remove_range(map, 0xfee00, 0xfeeff); > - if ( rc ) > - panic("IOMMU failed to remove Interrupt Address Range: %d\n", rc); > - This last chunk is not correct, if the interrupt address range is not removed, the local APIC page needs to be filtered out, so this should instead be: diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c index 8b1e0596b84a..c53626dfc69d 100644 --- a/xen/drivers/passthrough/x86/iommu.c +++ b/xen/drivers/passthrough/x86/iommu.c @@ -475,10 +475,11 @@ void __hwdom_init arch_iommu_hwdom_init(struct domain *d) if ( rc ) panic("IOMMU failed to remove Xen ranges: %d\n", rc); - /* Remove any overlap with the Interrupt Address Range. */ - rc = rangeset_remove_range(map, 0xfee00, 0xfeeff); + /* Remove any overlap with the local APIC page. */ + rc = rangeset_remove_range(map, paddr_to_pfn(mp_lapic_addr), + paddr_to_pfn(mp_lapic_addr)); if ( rc ) - panic("IOMMU failed to remove Interrupt Address Range: %d\n", rc); + panic("IOMMU failed to remove local APIC page: %d\n", rc); /* If emulating IO-APIC(s) make sure the base address is unmapped. */ if ( has_vioapic(d) )
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