Messages in this thread | | | From | Tianyu Lan <> | Date | Mon, 11 Feb 2019 16:10:40 +0800 | Subject | Re: [PATCH V3 2/3] HYPERV/IOMMU: Add Hyper-V stub IOMMU driver |
| |
Hi Alex: Thanks for your review.
On Fri, Feb 8, 2019 at 2:15 AM Alex Williamson <alex.williamson@redhat.com> wrote: > > On Thu, 7 Feb 2019 23:33:48 +0800 > lantianyu1986@gmail.com wrote: > > > From: Lan Tianyu <Tianyu.Lan@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.Lan@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,
Nice catch. I should check NR_CPUS here. Will update. Thanks.
-- Best regards Tianyu Lan
| |