Messages in this thread | | | From | Tianyu Lan <> | Date | Fri, 1 Feb 2019 13:45:08 +0800 | Subject | Re: [PATCH 2/3] HYPERV/IOMMU: Add Hyper-V stub IOMMU driver |
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Hi Vitaly: Thanks for your review.
On Thu, Jan 31, 2019 at 10:04 PM Vitaly Kuznetsov <vkuznets@redhat.com> wrote: > > lantianyu1986@gmail.com writes: > > > 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. > > > > Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com> > > --- > > drivers/iommu/Kconfig | 7 ++ > > drivers/iommu/Makefile | 1 + > > drivers/iommu/hyperv-iommu.c | 189 ++++++++++++++++++++++++++++++++++++++++++ > > drivers/iommu/irq_remapping.c | 3 + > > drivers/iommu/irq_remapping.h | 1 + > > 5 files changed, 201 insertions(+) > > create mode 100644 drivers/iommu/hyperv-iommu.c > > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > > index 45d7021..5c397c0 100644 > > --- a/drivers/iommu/Kconfig > > +++ b/drivers/iommu/Kconfig > > @@ -437,4 +437,11 @@ config QCOM_IOMMU > > help > > Support for IOMMU on certain Qualcomm SoCs. > > > > +config HYPERV_IOMMU > > + bool "Hyper-V stub IOMMU support" > > + depends on HYPERV > > + help > > + Hyper-V stub IOMMU driver provides capability to run > > + Linux guest with X2APIC mode enabled. > > + > > endif # IOMMU_SUPPORT > > diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile > > index a158a68..8c71a15 100644 > > --- a/drivers/iommu/Makefile > > +++ b/drivers/iommu/Makefile > > @@ -32,3 +32,4 @@ obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o > > obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o > > obj-$(CONFIG_S390_IOMMU) += s390-iommu.o > > obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o > > +obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o > > diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c > > new file mode 100644 > > index 0000000..a64b747 > > --- /dev/null > > +++ b/drivers/iommu/hyperv-iommu.c > > @@ -0,0 +1,189 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > + > > +#define pr_fmt(fmt) "HYPERV-IR: " fmt > > + > > +#include <linux/types.h> > > +#include <linux/interrupt.h> > > +#include <linux/irq.h> > > +#include <linux/iommu.h> > > +#include <linux/module.h> > > + > > +#include <asm/hw_irq.h> > > +#include <asm/io_apic.h> > > +#include <asm/irq_remapping.h> > > +#include <asm/hypervisor.h> > > + > > +#include "irq_remapping.h" > > + > > +/* > > + * According IO-APIC spec, IO APIC has a 24-entry Interrupt > > + * Redirection Table. > > + */ > > +#define IOAPIC_REMAPPING_ENTRY 24 > > KVM already defines KVM_IOAPIC_NUM_PINS - is this the same thing?
It's the same purpose IOMMU driver is out of KVM scope and so define a new one. Otherwise, this maybe changed in the future when add interrupt remapping function.
> > > + > > +static cpumask_t ioapic_max_cpumask = { CPU_BITS_NONE }; > > +struct irq_domain *ioapic_ir_domain; > > + > > +static int hyperv_ir_set_affinity(struct irq_data *data, > > + const struct cpumask *mask, bool force) > > +{ > > + struct irq_data *parent = data->parent_data; > > + struct irq_cfg *cfg = irqd_cfg(data); > > + struct IO_APIC_route_entry *entry; > > + cpumask_t cpumask; > > + int ret; > > + > > + cpumask_andnot(&cpumask, mask, &ioapic_max_cpumask); > > + > > + /* Return error If new irq affinity is out of ioapic_max_cpumask. */ > > + if (!cpumask_empty(&cpumask)) > > + return -EINVAL; > > + > > + ret = parent->chip->irq_set_affinity(parent, mask, force); > > + if (ret < 0 || ret == IRQ_SET_MASK_OK_DONE) > > + return ret; > > + > > + entry = data->chip_data; > > + entry->dest = cfg->dest_apicid; > > + entry->vector = cfg->vector; > > + send_cleanup_vector(cfg); > > + > > + return 0; > > +} > > + > > +static struct irq_chip hyperv_ir_chip = { > > + .name = "HYPERV-IR", > > + .irq_ack = apic_ack_irq, > > + .irq_set_affinity = hyperv_ir_set_affinity, > > +}; > > + > > +static int hyperv_irq_remapping_alloc(struct irq_domain *domain, > > + unsigned int virq, unsigned int nr_irqs, > > + void *arg) > > +{ > > + struct irq_alloc_info *info = arg; > > + struct IO_APIC_route_entry *entry; > > + struct irq_data *irq_data; > > + struct irq_desc *desc; > > + struct irq_cfg *cfg; > > + int ret = 0; > > + > > + if (!info || info->type != X86_IRQ_ALLOC_TYPE_IOAPIC || nr_irqs > 1) > > + return -EINVAL; > > + > > + ret = irq_domain_alloc_irqs_parent(domain, virq, nr_irqs, arg); > > + if (ret < 0) > > + goto fail; > > + > > + irq_data = irq_domain_get_irq_data(domain, virq); > > + cfg = irqd_cfg(irq_data); > > + if (!irq_data || !cfg) { > > + ret = -EINVAL; > > + goto fail; > > + } > > fail: label doesn't do anything, you can just return (and you actually > do on the first failure path).
Yes,will update.
> > > + > > + irq_data->chip = &hyperv_ir_chip; > > + > > + /* > > + * Save IOAPIC entry pointer here in order to set vector and > > + * and dest_apicid in the hyperv_irq_remappng_activate() > > and and
Nice catch.
> > > + * and hyperv_ir_set_affinity(). IOAPIC driver ignores > > + * cfg->dest_apicid and cfg->vector when irq remapping > > + * mode is enabled. Detail see ioapic_configure_entry(). > > I would re-phrase this a bit: > > /* > * IOAPIC entry pointer is saved in chip_data to allow > * hyperv_irq_remappng_activate()/hyperv_ir_set_affinity() to set > * vector and dest_apicid. cfg->vector and cfg->dest_apicid are > * ignorred when IRQ remapping is enabled. See ioapic_configure_entry(). > */ > > But I'm still a bit confused. Hope others are not.
This is better. Thanks.
> > > + */ > > + irq_data->chip_data = entry = info->ioapic_entry; > > + > > I personally dislike double assignments, hard to remember which one > happens first :-)
OK. will update.
> > > + /* > > + * Hypver-V IO APIC irq affinity should be in the scope of > > + * ioapic_max_cpumask because no irq remapping support. > > + */ > > + desc = irq_data_to_desc(irq_data); > > + cpumask_and(desc->irq_common_data.affinity, > > + desc->irq_common_data.affinity, > > + &ioapic_max_cpumask); > > + > > + fail: > > + return ret; > > +} > > + > > +static void hyperv_irq_remapping_free(struct irq_domain *domain, > > + unsigned int virq, unsigned int nr_irqs) > > +{ > > + irq_domain_free_irqs_common(domain, virq, nr_irqs); > > +} > > + > > +static int hyperv_irq_remappng_activate(struct irq_domain *domain, > > + struct irq_data *irq_data, bool reserve) > > +{ > > + struct irq_cfg *cfg = irqd_cfg(irq_data); > > + struct IO_APIC_route_entry *entry = irq_data->chip_data; > > + > > + entry->dest = cfg->dest_apicid; > > + entry->vector = cfg->vector; > > + > > + return 0; > > +} > > + > > +static struct irq_domain_ops hyperv_ir_domain_ops = { > > + .alloc = hyperv_irq_remapping_alloc, > > + .free = hyperv_irq_remapping_free, > > + .activate = hyperv_irq_remappng_activate, > > +}; > > + > > +static int __init hyperv_prepare_irq_remapping(void) > > +{ > > + struct fwnode_handle *fn; > > + u32 apic_id; > > + int i; > > + > > + if (x86_hyper_type != X86_HYPER_MS_HYPERV || > > + !x2apic_supported()) > > + return -ENODEV; > > + > > + fn = irq_domain_alloc_named_id_fwnode("HYPERV-IR", 0); > > + if (!fn) > > + return -EFAULT; > > + > > + 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. > > + * 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 255. > > + */ > > + for (i = 0; i < 256; i++) { > > + apic_id = cpu_physical_id(i); > > + if (apic_id > 255) > > + continue; > > + > > + cpumask_set_cpu(i, &ioapic_max_cpumask); > > + } > > This is probably not an issue right now, but what if we have > 256 CPUs? > Assuming there are no CPUs with the same APIC is, would it be better to > go through all of them seeting bits in ioapic_max_cpumask accordingly? > (Imagine a situation when CPU257 has APIC id = 1).
The APiC ID assignment with "CPUx"accords the order of local APIC entry in the ACPI MADT table. We got that the order will be monotonic increasing from Hyper-V team .I will add this in the comment to avoid confusion. APIC IDs reflects cpu topology and so there maybe some APIC ID gaps(e.g, cpu number in one socket is a number of power of 2).
> > > + > > + return 0; > > +} > > + > > +static int __init hyperv_enable_irq_remapping(void) > > +{ > > + return IRQ_REMAP_X2APIC_MODE; > > +} > > + > > +static struct irq_domain *hyperv_get_ir_irq_domain(struct irq_alloc_info *info) > > +{ > > + if (info->type == X86_IRQ_ALLOC_TYPE_IOAPIC) > > + return ioapic_ir_domain; > > + else > > + return NULL; > > +} > > + > > +struct irq_remap_ops hyperv_irq_remap_ops = { > > + .prepare = hyperv_prepare_irq_remapping, > > + .enable = hyperv_enable_irq_remapping, > > + .get_ir_irq_domain = hyperv_get_ir_irq_domain, > > +}; > > diff --git a/drivers/iommu/irq_remapping.c b/drivers/iommu/irq_remapping.c > > index b94ebd4..81cf290 100644 > > --- a/drivers/iommu/irq_remapping.c > > +++ b/drivers/iommu/irq_remapping.c > > @@ -103,6 +103,9 @@ int __init irq_remapping_prepare(void) > > else if (IS_ENABLED(CONFIG_AMD_IOMMU) && > > amd_iommu_irq_ops.prepare() == 0) > > remap_ops = &amd_iommu_irq_ops; > > + else if (IS_ENABLED(CONFIG_HYPERV_IOMMU) && > > + hyperv_irq_remap_ops.prepare() == 0) > > + remap_ops = &hyperv_irq_remap_ops; > > else > > return -ENOSYS; > > Here we act under assumption that Intel/AMD IOMMUs will never be exposed > under Hyper-V. It may make sense to actually reverse the order of the > check: check PV IOMMUs _before_ we actually check for hardware ones.
Yes, this will be better for Hyper-V case but KVM guest and bare metal use Intel/AMD IOMMU driver. The function is just called once during boot up and so check order will not affect boot time too much.
@Joerg Roedel Could you have a look this? Thanks.
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