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, February 3, 2021 4:47 AM
> 
> On Wed, Jan 27, 2021 at 05:47:08AM +0000, Michael Kelley wrote:
> > 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.
> 
> Fixed.
> 
> >
> > > +}
> > > +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. :-)
> >
> 
> Indeed. I will see about factoring out a function.

If factoring out a separate helper function is clumsy, just having the parallel code
in the two functions be as similar as possible makes it easier to see what's the
same and what's different.

> 
> > Same 64 vCPU comment applies here as well.
> >
> 
> This is changed to use vpset instead. Took me a bit of time to get it
> working because document is a bit lacking.
> 
> >
> > > +}
> > > +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?
> >
> 
> Before v5 (or v4?) IO-APIC was not handled via Hyper-V IOMMU. Now it is.
> 
> Patch 4 has become redundant with that change. I already dropped patch 4
> in the v6 branch I have locally.
> 
> > >  		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;
> > > +	}
> > > +
> [...]
> > > +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.
> 
> The usage of irq_data->chip_data is different in these two functions.
> 
> In this function, we're sure it is correctly allocated by
> hyperv_root_ir_remapping_alloc at some point before.
> 
> In hv_irq_compose_msi_msg, irq_data->chip_data is instead used as a
> temporary place to stash some state that is controlled solely by the
> said function.
> 
> Once we get to the point of introducing a paravirtualized IOMMU for the
> root partition, we can then unify these two paths.

OK, thanks for the explanation.

> 
> >
> > > +	    && 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?
> >
> 
> See above.
> 
> I can perhaps tweak the logic a bit to reuse the same entry, but the
> overall design won't change. I opted to always reallocate because that
> looked more straight-forward to me.
> 
> Let me know if you feel strongly about reusing.

I don't feel strongly about reusing.  I was just comparing/contrasting
the two functions.

> 
> > > +	}
> > > +
> > > +
> > > +	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. :-)
> >
> 
> Unlike hv_map_ioapic_interrupt and hv_map_msi_interrupt, which can
> benefit from unifying now, this and hv_irq_compose_msi_msg will need to
> wait till we have an IOMMU for the reason I stated above.

OK.  Just having the code in the two functions be more parallel where
possible would make it easier to see similarities and differences.  But
it's not a big deal.

> 
> > > +
> > > +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 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.
> 
> There is no need to do that. By the time this function returns, irq_data
> will be gone too -- freed by irq_domain_free_irqs_common.

OK

> 
> >
> > > +			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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