On Thu, 7 Feb 2019 23:33:48 +0800 lantianyu1...@gmail.com wrote: > From: Lan Tianyu <tianyu....@microsoft.com> > > On the bare metal, enabling X2APIC mode requires interrupt remapping > function which helps to deliver irq to cpu with 32-bit APIC ID. > Hyper-V doesn't provide interrupt remapping function so far and Hyper-V > MSI protocol already supports to deliver interrupt to the CPU whose > virtual processor index is more than 255. IO-APIC interrupt still has > 8-bit APIC ID limitation. > > This patch is to add Hyper-V stub IOMMU driver in order to enable > X2APIC mode successfully in Hyper-V Linux guest. The driver returns X2APIC > interrupt remapping capability when X2APIC mode is available. Otherwise, > it creates a Hyper-V irq domain to limit IO-APIC interrupts' affinity > and make sure cpus assigned with IO-APIC interrupt have 8-bit APIC ID. > > Define 24 IO-APIC remapping entries because Hyper-V only expose one > single IO-APIC and one IO-APIC has 24 pins according IO-APIC spec( > https://pdos.csail.mit.edu/6.828/2016/readings/ia32/ioapic.pdf). > > Signed-off-by: Lan Tianyu <tianyu....@microsoft.com> > --- > Change since v2: > - Improve comment about why save IO-APIC entry in the irq chip data. > - Some code improvement. > - Improve statement in the IOMMU Kconfig. > > Change since v1: > - Remove unused pr_fmt > - Make ioapic_ir_domain as static variable > - Remove unused variables cfg and entry in the > hyperv_irq_remapping_alloc() > - Fix comments > --- > drivers/iommu/Kconfig | 8 ++ > drivers/iommu/Makefile | 1 + > drivers/iommu/hyperv-iommu.c | 194 > ++++++++++++++++++++++++++++++++++++++++++ > drivers/iommu/irq_remapping.c | 3 + > drivers/iommu/irq_remapping.h | 1 + > 5 files changed, 207 insertions(+) > create mode 100644 drivers/iommu/hyperv-iommu.c ... > diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c > new file mode 100644 > index 0000000..d8572c5 > --- /dev/null > +++ b/drivers/iommu/hyperv-iommu.c ... > +static int __init hyperv_prepare_irq_remapping(void) > +{ > + struct fwnode_handle *fn; > + int i; > + > + if (!hypervisor_is_type(x86_hyper_type) || > + !x2apic_supported()) > + return -ENODEV; > + > + fn = irq_domain_alloc_named_id_fwnode("HYPERV-IR", 0); > + if (!fn) > + return -ENOMEM; > + > + ioapic_ir_domain = > + irq_domain_create_hierarchy(arch_get_ir_parent_domain(), > + 0, IOAPIC_REMAPPING_ENTRY, fn, > + &hyperv_ir_domain_ops, NULL); > + > + irq_domain_free_fwnode(fn); > + > + /* > + * Hyper-V doesn't provide irq remapping function for > + * IO-APIC and so IO-APIC only accepts 8-bit APIC ID. > + * Cpu's APIC ID is read from ACPI MADT table and APIC IDs > + * in the MADT table on Hyper-v are sorted monotonic increasingly. > + * APIC ID reflects cpu topology. There maybe some APIC ID > + * gaps when cpu number in a socket is not power of two. Prepare > + * max cpu affinity for IOAPIC irqs. Scan cpu 0-255 and set cpu > + * into ioapic_max_cpumask if its APIC ID is less than 256. > + */ > + for (i = 0; i < 256; i++) > + if (cpu_physical_id(i) < 256) > + cpumask_set_cpu(i, &ioapic_max_cpumask);
This looks sketchy. What if NR_CPUS is less than 256? Thanks, Alex > + > + return 0; > +}
