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

Michael Kelley
2021-02-04T19:29:41Z

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
> >