RE: [PATCH v5 16/16] iommu/hyperv: setup an IO-APIC IRQ remapping domain for root partition

[Michael Kelley via iommu <iommu@lists.linux-foundation.org>]

From: Wei Liu <wei.liu@kernel.org> Sent: Wednesday, January 20, 2021 4:01 AM
> 
> Just like MSI/MSI-X, IO-APIC interrupts are remapped by Microsoft
> Hypervisor when Linux runs as the root partition. Implement an IRQ
> domain to handle mapping and unmapping of IO-APIC interrupts.
> 
> Signed-off-by: Wei Liu <wei.liu@kernel.org>
> ---
>  arch/x86/hyperv/irqdomain.c     |  54 ++++++++++
>  arch/x86/include/asm/mshyperv.h |   4 +
>  drivers/iommu/hyperv-iommu.c    | 179 +++++++++++++++++++++++++++++++-
>  3 files changed, 233 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> index 19637cd60231..8e2b4e478b70 100644
> --- a/arch/x86/hyperv/irqdomain.c
> +++ b/arch/x86/hyperv/irqdomain.c
> @@ -330,3 +330,57 @@ struct irq_domain * __init hv_create_pci_msi_domain(void)
>  }
> 
>  #endif /* CONFIG_PCI_MSI */
> +
> +int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry)
> +{
> +	union hv_device_id device_id;
> +
> +	device_id.as_uint64 = 0;
> +	device_id.device_type = HV_DEVICE_TYPE_IOAPIC;
> +	device_id.ioapic.ioapic_id = (u8)ioapic_id;
> +
> +	return hv_unmap_interrupt(device_id.as_uint64, entry) & HV_HYPERCALL_RESULT_MASK;

The masking is already done in hv_unmap_interrupt.

> +}
> +EXPORT_SYMBOL_GPL(hv_unmap_ioapic_interrupt);
> +
> +int hv_map_ioapic_interrupt(int ioapic_id, bool level, int vcpu, int vector,
> +		struct hv_interrupt_entry *entry)
> +{
> +	unsigned long flags;
> +	struct hv_input_map_device_interrupt *input;
> +	struct hv_output_map_device_interrupt *output;
> +	union hv_device_id device_id;
> +	struct hv_device_interrupt_descriptor *intr_desc;
> +	u16 status;
> +
> +	device_id.as_uint64 = 0;
> +	device_id.device_type = HV_DEVICE_TYPE_IOAPIC;
> +	device_id.ioapic.ioapic_id = (u8)ioapic_id;
> +
> +	local_irq_save(flags);
> +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> +	output = *this_cpu_ptr(hyperv_pcpu_output_arg);
> +	memset(input, 0, sizeof(*input));
> +	intr_desc = &input->interrupt_descriptor;
> +	input->partition_id = hv_current_partition_id;
> +	input->device_id = device_id.as_uint64;
> +	intr_desc->interrupt_type = HV_X64_INTERRUPT_TYPE_FIXED;
> +	intr_desc->target.vector = vector;
> +	intr_desc->vector_count = 1;
> +
> +	if (level)
> +		intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_LEVEL;
> +	else
> +		intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_EDGE;
> +
> +	__set_bit(vcpu, (unsigned long *)&intr_desc->target.vp_mask);
> +
> +	status = hv_do_rep_hypercall(HVCALL_MAP_DEVICE_INTERRUPT, 0, 0, input, output) &
> +			 HV_HYPERCALL_RESULT_MASK;
> +	local_irq_restore(flags);
> +
> +	*entry = output->interrupt_entry;
> +
> +	return status;

As a cross-check, I was comparing this code against hv_map_msi_interrupt().  They are
mostly parallel, though some of the assignments are done in a different order.  It's a nit,
but making them as parallel as possible would be nice. :-)

Same 64 vCPU comment applies here as well.


> +}
> +EXPORT_SYMBOL_GPL(hv_map_ioapic_interrupt);
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index ccc849e25d5e..345d7c6f8c37 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -263,6 +263,10 @@ static inline void hv_set_msi_entry_from_desc(union
> hv_msi_entry *msi_entry,
> 
>  struct irq_domain *hv_create_pci_msi_domain(void);
> 
> +int hv_map_ioapic_interrupt(int ioapic_id, bool level, int vcpu, int vector,
> +		struct hv_interrupt_entry *entry);
> +int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry);
> +
>  #else /* CONFIG_HYPERV */
>  static inline void hyperv_init(void) {}
>  static inline void hyperv_setup_mmu_ops(void) {}
> diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
> index b7db6024e65c..6d35e4c303c6 100644
> --- a/drivers/iommu/hyperv-iommu.c
> +++ b/drivers/iommu/hyperv-iommu.c
> @@ -116,30 +116,43 @@ static const struct irq_domain_ops hyperv_ir_domain_ops = {
>  	.free = hyperv_irq_remapping_free,
>  };
> 
> +static const struct irq_domain_ops hyperv_root_ir_domain_ops;
>  static int __init hyperv_prepare_irq_remapping(void)
>  {
>  	struct fwnode_handle *fn;
>  	int i;
> +	const char *name;
> +	const struct irq_domain_ops *ops;
> 
>  	if (!hypervisor_is_type(X86_HYPER_MS_HYPERV) ||
>  	    x86_init.hyper.msi_ext_dest_id() ||
> -	    !x2apic_supported() || hv_root_partition)
> +	    !x2apic_supported())

Any reason that the check for hv_root_partition was added
in patch #4  of this series, and then removed here?  Could
patch #4 just be dropped?

>  		return -ENODEV;
> 
> -	fn = irq_domain_alloc_named_id_fwnode("HYPERV-IR", 0);
> +	if (hv_root_partition) {
> +		name = "HYPERV-ROOT-IR";
> +		ops = &hyperv_root_ir_domain_ops;
> +	} else {
> +		name = "HYPERV-IR";
> +		ops = &hyperv_ir_domain_ops;
> +	}
> +
> +	fn = irq_domain_alloc_named_id_fwnode(name, 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);
> +				0, IOAPIC_REMAPPING_ENTRY, fn, ops, NULL);
> 
>  	if (!ioapic_ir_domain) {
>  		irq_domain_free_fwnode(fn);
>  		return -ENOMEM;
>  	}
> 
> +	if (hv_root_partition)
> +		return 0; /* The rest is only relevant to guests */
> +
>  	/*
>  	 * Hyper-V doesn't provide irq remapping function for
>  	 * IO-APIC and so IO-APIC only accepts 8-bit APIC ID.
> @@ -167,4 +180,162 @@ struct irq_remap_ops hyperv_irq_remap_ops = {
>  	.enable			= hyperv_enable_irq_remapping,
>  };
> 
> +/* IRQ remapping domain when Linux runs as the root partition */
> +struct hyperv_root_ir_data {
> +	u8 ioapic_id;
> +	bool is_level;
> +	struct hv_interrupt_entry entry;
> +};
> +
> +static void
> +hyperv_root_ir_compose_msi_msg(struct irq_data *irq_data, struct msi_msg *msg)
> +{
> +	u16 status;
> +	u32 vector;
> +	struct irq_cfg *cfg;
> +	int ioapic_id;
> +	struct cpumask *affinity;
> +	int cpu, vcpu;
> +	struct hv_interrupt_entry entry;
> +	struct hyperv_root_ir_data *data = irq_data->chip_data;
> +	struct IO_APIC_route_entry e;
> +
> +	cfg = irqd_cfg(irq_data);
> +	affinity = irq_data_get_effective_affinity_mask(irq_data);
> +	cpu = cpumask_first_and(affinity, cpu_online_mask);
> +	vcpu = hv_cpu_number_to_vp_number(cpu);
> +
> +	vector = cfg->vector;
> +	ioapic_id = data->ioapic_id;
> +
> +	if (data->entry.source == HV_DEVICE_TYPE_IOAPIC

Does 'data' need to be checked to be non-NULL?  The parallel code in
hv_irq_compose_msi_msg() makes such a check.

> +	    && data->entry.ioapic_rte.as_uint64) {
> +		entry = data->entry;
> +
> +		status = hv_unmap_ioapic_interrupt(ioapic_id, &entry);
> +
> +		if (status != HV_STATUS_SUCCESS)
> +			pr_debug("%s: unexpected unmap status %d\n", __func__, status);
> +
> +		data->entry.ioapic_rte.as_uint64 = 0;
> +		data->entry.source = 0; /* Invalid source */

Again comparing, hv_irq_compose_msi_msg() frees the old
entry, and then allocates a new one.   This code reuses the old entry. 
Any reason for the difference?

> +	}
> +
> +
> +	status = hv_map_ioapic_interrupt(ioapic_id, data->is_level, vcpu,
> +					vector, &entry);
> +
> +	if (status != HV_STATUS_SUCCESS) {
> +		pr_err("%s: map hypercall failed, status %d\n", __func__, status);
> +		return;
> +	}
> +
> +	data->entry = entry;
> +
> +	/* Turn it into an IO_APIC_route_entry, and generate MSI MSG. */
> +	e.w1 = entry.ioapic_rte.low_uint32;
> +	e.w2 = entry.ioapic_rte.high_uint32;
> +
> +	memset(msg, 0, sizeof(*msg));
> +	msg->arch_data.vector = e.vector;
> +	msg->arch_data.delivery_mode = e.delivery_mode;
> +	msg->arch_addr_lo.dest_mode_logical = e.dest_mode_logical;
> +	msg->arch_addr_lo.dmar_format = e.ir_format;
> +	msg->arch_addr_lo.dmar_index_0_14 = e.ir_index_0_14;
> +}

Having this whole function be more parallel to hv_irq_compose_msi_msg()
would be nice. :-)

> +
> +static int hyperv_root_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);
> +	int ret;
> +
> +	ret = parent->chip->irq_set_affinity(parent, mask, force);
> +	if (ret < 0 || ret == IRQ_SET_MASK_OK_DONE)
> +		return ret;
> +
> +	send_cleanup_vector(cfg);
> +
> +	return 0;
> +}
> +
> +static struct irq_chip hyperv_root_ir_chip = {
> +	.name			= "HYPERV-ROOT-IR",
> +	.irq_ack		= apic_ack_irq,
> +	.irq_set_affinity	= hyperv_root_ir_set_affinity,
> +	.irq_compose_msi_msg	= hyperv_root_ir_compose_msi_msg,
> +};
> +
> +static int hyperv_root_irq_remapping_alloc(struct irq_domain *domain,
> +				     unsigned int virq, unsigned int nr_irqs,
> +				     void *arg)
> +{
> +	struct irq_alloc_info *info = arg;
> +	struct irq_data *irq_data;
> +	struct hyperv_root_ir_data *data;
> +	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)
> +		return ret;
> +
> +	data = kzalloc(sizeof(*data), GFP_KERNEL);
> +	if (!data) {
> +		irq_domain_free_irqs_common(domain, virq, nr_irqs);
> +		return -ENOMEM;
> +	}
> +
> +	irq_data = irq_domain_get_irq_data(domain, virq);
> +	if (!irq_data) {
> +		kfree(data);
> +		irq_domain_free_irqs_common(domain, virq, nr_irqs);
> +		return -EINVAL;
> +	}
> +
> +	data->ioapic_id = info->devid;
> +	data->is_level = info->ioapic.is_level;
> +
> +	irq_data->chip = &hyperv_root_ir_chip;
> +	irq_data->chip_data = data;
> +
> +	return 0;
> +}
> +
> +static void hyperv_root_irq_remapping_free(struct irq_domain *domain,
> +				 unsigned int virq, unsigned int nr_irqs)
> +{
> +	struct irq_data *irq_data;
> +	struct hyperv_root_ir_data *data;
> +	struct hv_interrupt_entry *e;
> +	int i;
> +
> +	for (i = 0; i < nr_irqs; i++) {
> +		irq_data = irq_domain_get_irq_data(domain, virq + i);
> +
> +		if (irq_data && irq_data->chip_data) {
> +			data = irq_data->chip_data;

Set irq_data->chip_data to NULL?  That seems to be done in other
similar places in your code.

> +			e = &data->entry;
> +
> +			if (e->source == HV_DEVICE_TYPE_IOAPIC
> +			      && e->ioapic_rte.as_uint64)
> +				hv_unmap_ioapic_interrupt(data->ioapic_id,
> +							&data->entry);
> +
> +			kfree(data);
> +		}
> +	}
> +
> +	irq_domain_free_irqs_common(domain, virq, nr_irqs);
> +}
> +
> +static const struct irq_domain_ops hyperv_root_ir_domain_ops = {
> +	.select = hyperv_irq_remapping_select,
> +	.alloc = hyperv_root_irq_remapping_alloc,
> +	.free = hyperv_root_irq_remapping_free,
> +};
> +
>  #endif
> --
> 2.20.1

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