RE: [PATCH v5 15/16] x86/hyperv: implement an MSI domain for root partition

[Michael Kelley]

From: Wei Liu <wei.liu@xxxxxxxxxx> Sent: Wednesday, January 20, 2021 4:01 AM
> 
> When Linux runs as the root partition on Microsoft Hypervisor, its
> interrupts are remapped.  Linux will need to explicitly map and unmap
> interrupts for hardware.
> 
> Implement an MSI domain to issue the correct hypercalls. And initialize
> this irqdomain as the default MSI irq domain.
> 
> Signed-off-by: Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx>
> Co-Developed-by: Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx>
> Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx>
> ---
> v4: Fix compilation issue when CONFIG_PCI_MSI is not set.
> v3: build irqdomain.o for 32bit as well.

I'm not clear on the intent for 32-bit builds.  Given that hv_proc.c is built
only for 64-bit, I'm assuming running Linux in the root partition
is only functional for 64-bit builds.  So is the goal simply that 32-bit
builds will compile correctly?  Seems like maybe there should be
a CONFIG option for running Linux in the root partition, and that
option would force 64-bit.

> v2: This patch is simplified due to upstream changes.
> ---
>  arch/x86/hyperv/Makefile        |   2 +-
>  arch/x86/hyperv/hv_init.c       |   9 +
>  arch/x86/hyperv/irqdomain.c     | 332 ++++++++++++++++++++++++++++++++
>  arch/x86/include/asm/mshyperv.h |   2 +
>  4 files changed, 344 insertions(+), 1 deletion(-)
>  create mode 100644 arch/x86/hyperv/irqdomain.c
> 
> diff --git a/arch/x86/hyperv/Makefile b/arch/x86/hyperv/Makefile
> index 565358020921..48e2c51464e8 100644
> --- a/arch/x86/hyperv/Makefile
> +++ b/arch/x86/hyperv/Makefile
> @@ -1,5 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0-only
> -obj-y			:= hv_init.o mmu.o nested.o
> +obj-y			:= hv_init.o mmu.o nested.o irqdomain.o
>  obj-$(CONFIG_X86_64)	+= hv_apic.o hv_proc.o
> 
>  ifdef CONFIG_X86_64
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index ad8e77859b32..1cb2f7d1850a 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -484,6 +484,15 @@ void __init hyperv_init(void)
> 
>  	BUG_ON(hv_root_partition && hv_current_partition_id == ~0ull);
> 
> +#ifdef CONFIG_PCI_MSI
> +	/*
> +	 * If we're running as root, we want to create our own PCI MSI domain.
> +	 * We can't set this in hv_pci_init because that would be too late.
> +	 */
> +	if (hv_root_partition)
> +		x86_init.irqs.create_pci_msi_domain = hv_create_pci_msi_domain;
> +#endif
> +
>  	return;
> 
>  remove_cpuhp_state:
> diff --git a/arch/x86/hyperv/irqdomain.c b/arch/x86/hyperv/irqdomain.c
> new file mode 100644
> index 000000000000..19637cd60231
> --- /dev/null
> +++ b/arch/x86/hyperv/irqdomain.c
> @@ -0,0 +1,332 @@
> +// SPDX-License-Identifier: GPL-2.0
> +//
> +// Irqdomain for Linux to run as the root partition on Microsoft Hypervisor.
> +//
> +// Authors:
> +//   Sunil Muthuswamy <sunilmut@xxxxxxxxxxxxx>
> +//   Wei Liu <wei.liu@xxxxxxxxxx>

I think the // comment style should only be used for the SPDX line.

> +
> +#include <linux/pci.h>
> +#include <linux/irq.h>
> +#include <asm/mshyperv.h>
> +
> +static int hv_unmap_interrupt(u64 id, struct hv_interrupt_entry *old_entry)
> +{
> +	unsigned long flags;
> +	struct hv_input_unmap_device_interrupt *input;
> +	struct hv_interrupt_entry *intr_entry;
> +	u16 status;
> +
> +	local_irq_save(flags);
> +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> +
> +	memset(input, 0, sizeof(*input));
> +	intr_entry = &input->interrupt_entry;
> +	input->partition_id = hv_current_partition_id;
> +	input->device_id = id;
> +	*intr_entry = *old_entry;
> +
> +	status = hv_do_rep_hypercall(HVCALL_UNMAP_DEVICE_INTERRUPT, 0, 0, input, NULL) &
> +			 HV_HYPERCALL_RESULT_MASK;
> +	local_irq_restore(flags);
> +
> +	return status;
> +}
> +
> +#ifdef CONFIG_PCI_MSI
> +struct rid_data {
> +	struct pci_dev *bridge;
> +	u32 rid;
> +};
> +
> +static int get_rid_cb(struct pci_dev *pdev, u16 alias, void *data)
> +{
> +	struct rid_data *rd = data;
> +	u8 bus = PCI_BUS_NUM(rd->rid);
> +
> +	if (pdev->bus->number != bus || PCI_BUS_NUM(alias) != bus) {
> +		rd->bridge = pdev;
> +		rd->rid = alias;
> +	}
> +
> +	return 0;
> +}
> +
> +static union hv_device_id hv_build_pci_dev_id(struct pci_dev *dev)
> +{
> +	union hv_device_id dev_id;
> +	struct rid_data data = {
> +		.bridge = NULL,
> +		.rid = PCI_DEVID(dev->bus->number, dev->devfn)
> +	};
> +
> +	pci_for_each_dma_alias(dev, get_rid_cb, &data);
> +
> +	dev_id.as_uint64 = 0;
> +	dev_id.device_type = HV_DEVICE_TYPE_PCI;
> +	dev_id.pci.segment = pci_domain_nr(dev->bus);
> +
> +	dev_id.pci.bdf.bus = PCI_BUS_NUM(data.rid);
> +	dev_id.pci.bdf.device = PCI_SLOT(data.rid);
> +	dev_id.pci.bdf.function = PCI_FUNC(data.rid);
> +	dev_id.pci.source_shadow = HV_SOURCE_SHADOW_NONE;
> +
> +	if (data.bridge) {
> +		int pos;
> +
> +		/*
> +		 * Microsoft Hypervisor requires a bus range when the bridge is
> +		 * running in PCI-X mode.
> +		 *
> +		 * To distinguish conventional vs PCI-X bridge, we can check
> +		 * the bridge's PCI-X Secondary Status Register, Secondary Bus
> +		 * Mode and Frequency bits. See PCI Express to PCI/PCI-X Bridge
> +		 * Specification Revision 1.0 5.2.2.1.3.
> +		 *
> +		 * Value zero means it is in conventional mode, otherwise it is
> +		 * in PCI-X mode.
> +		 */
> +
> +		pos = pci_find_capability(data.bridge, PCI_CAP_ID_PCIX);
> +		if (pos) {
> +			u16 status;
> +
> +			pci_read_config_word(data.bridge, pos +
> +					PCI_X_BRIDGE_SSTATUS, &status);
> +
> +			if (status & PCI_X_SSTATUS_FREQ) {
> +				/* Non-zero, PCI-X mode */
> +				u8 sec_bus, sub_bus;
> +
> +				dev_id.pci.source_shadow = HV_SOURCE_SHADOW_BRIDGE_BUS_RANGE;
> +
> +				pci_read_config_byte(data.bridge, PCI_SECONDARY_BUS, &sec_bus);
> +				dev_id.pci.shadow_bus_range.secondary_bus = sec_bus;
> +				pci_read_config_byte(data.bridge, PCI_SUBORDINATE_BUS, &sub_bus);
> +				dev_id.pci.shadow_bus_range.subordinate_bus = sub_bus;
> +			}
> +		}
> +	}
> +
> +	return dev_id;
> +}
> +
> +static int hv_map_msi_interrupt(struct pci_dev *dev, int vcpu, int vector,
> +				struct hv_interrupt_entry *entry)
> +{
> +	struct hv_input_map_device_interrupt *input;
> +	struct hv_output_map_device_interrupt *output;
> +	struct hv_device_interrupt_descriptor *intr_desc;
> +	unsigned long flags;
> +	u16 status;
> +
> +	local_irq_save(flags);
> +
> +	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
> +	output = *this_cpu_ptr(hyperv_pcpu_output_arg);
> +
> +	intr_desc = &input->interrupt_descriptor;
> +	memset(input, 0, sizeof(*input));
> +	input->partition_id = hv_current_partition_id;
> +	input->device_id = hv_build_pci_dev_id(dev).as_uint64;
> +	intr_desc->interrupt_type = HV_X64_INTERRUPT_TYPE_FIXED;
> +	intr_desc->trigger_mode = HV_INTERRUPT_TRIGGER_MODE_EDGE;
> +	intr_desc->vector_count = 1;
> +	intr_desc->target.vector = vector;
> +	__set_bit(vcpu, (unsigned long*)&intr_desc->target.vp_mask);

This is using the CPU bitmap format that supports up to 64 vCPUs.  Any reason not
to use the format that supports a larger number of CPUs?   In either case, perhaps
a check for the value of vcpu against the max of 64 (or the larger number if you
change the bitmap format) would be appropriate.

> +
> +	status = hv_do_rep_hypercall(HVCALL_MAP_DEVICE_INTERRUPT, 0, 0, input, output) &
> +			 HV_HYPERCALL_RESULT_MASK;
> +	*entry = output->interrupt_entry;
> +
> +	local_irq_restore(flags);
> +
> +	if (status != HV_STATUS_SUCCESS)
> +		pr_err("%s: hypercall failed, status %d\n", __func__, status);
> +
> +	return status;
> +}
> +
> +static inline void entry_to_msi_msg(struct hv_interrupt_entry *entry, struct msi_msg *msg)
> +{
> +	/* High address is always 0 */
> +	msg->address_hi = 0;
> +	msg->address_lo = entry->msi_entry.address.as_uint32;
> +	msg->data = entry->msi_entry.data.as_uint32;
> +}
> +
> +static int hv_unmap_msi_interrupt(struct pci_dev *dev, struct hv_interrupt_entry *old_entry);
> +static void hv_irq_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
> +{
> +	struct msi_desc *msidesc;
> +	struct pci_dev *dev;
> +	struct hv_interrupt_entry out_entry, *stored_entry;
> +	struct irq_cfg *cfg = irqd_cfg(data);
> +	struct cpumask *affinity;
> +	int cpu, vcpu;
> +	u16 status;
> +
> +	msidesc = irq_data_get_msi_desc(data);
> +	dev = msi_desc_to_pci_dev(msidesc);
> +
> +	if (!cfg) {
> +		pr_debug("%s: cfg is NULL", __func__);
> +		return;
> +	}
> +
> +	affinity = irq_data_get_effective_affinity_mask(data);
> +	cpu = cpumask_first_and(affinity, cpu_online_mask);
> +	vcpu = hv_cpu_number_to_vp_number(cpu);
> +
> +	if (data->chip_data) {
> +		/*
> +		 * This interrupt is already mapped. Let's unmap first.
> +		 *
> +		 * We don't use retarget interrupt hypercalls here because
> +		 * Microsoft Hypervisor doens't allow root to change the vector
> +		 * or specify VPs outside of the set that is initially used
> +		 * during mapping.
> +		 */
> +		stored_entry = data->chip_data;
> +		data->chip_data = NULL;
> +
> +		status = hv_unmap_msi_interrupt(dev, stored_entry);
> +
> +		kfree(stored_entry);
> +
> +		if (status != HV_STATUS_SUCCESS) {
> +			pr_debug("%s: failed to unmap, status %d", __func__, status);
> +			return;
> +		}
> +	}
> +
> +	stored_entry = kzalloc(sizeof(*stored_entry), GFP_ATOMIC);
> +	if (!stored_entry) {
> +		pr_debug("%s: failed to allocate chip data\n", __func__);
> +		return;
> +	}
> +
> +	status = hv_map_msi_interrupt(dev, vcpu, cfg->vector, &out_entry);
> +	if (status != HV_STATUS_SUCCESS) {
> +		kfree(stored_entry);
> +		return;
> +	}
> +
> +	*stored_entry = out_entry;
> +	data->chip_data = stored_entry;
> +	entry_to_msi_msg(&out_entry, msg);
> +
> +	return;
> +}
> +
> +static int hv_unmap_msi_interrupt(struct pci_dev *dev, struct hv_interrupt_entry
> *old_entry)
> +{
> +	return hv_unmap_interrupt(hv_build_pci_dev_id(dev).as_uint64, old_entry)
> +		& HV_HYPERCALL_RESULT_MASK;

The masking with HV_HYPERCALL_RESULT_MASK is already done in
hv_unmap_interrupt().

> +}
> +
> +static void hv_teardown_msi_irq_common(struct pci_dev *dev, struct msi_desc
> *msidesc, int irq)
> +{
> +	u16 status;
> +	struct hv_interrupt_entry old_entry;
> +	struct irq_desc *desc;
> +	struct irq_data *data;
> +	struct msi_msg msg;
> +
> +	desc = irq_to_desc(irq);
> +	if (!desc) {
> +		pr_debug("%s: no irq desc\n", __func__);
> +		return;
> +	}
> +
> +	data = &desc->irq_data;
> +	if (!data) {
> +		pr_debug("%s: no irq data\n", __func__);
> +		return;
> +	}
> +
> +	if (!data->chip_data) {
> +		pr_debug("%s: no chip data\n!", __func__);
> +		return;
> +	}
> +
> +	old_entry = *(struct hv_interrupt_entry *)data->chip_data;
> +	entry_to_msi_msg(&old_entry, &msg);
> +
> +	kfree(data->chip_data);
> +	data->chip_data = NULL;
> +
> +	status = hv_unmap_msi_interrupt(dev, &old_entry);
> +
> +	if (status != HV_STATUS_SUCCESS) {
> +		pr_err("%s: hypercall failed, status %d\n", __func__, status);
> +		return;
> +	}
> +}
> +
> +static void hv_msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
> +{
> +	int i;
> +	struct msi_desc *entry;
> +	struct pci_dev *pdev;
> +
> +	if (WARN_ON_ONCE(!dev_is_pci(dev)))
> +		return;
> +
> +	pdev = to_pci_dev(dev);
> +
> +	for_each_pci_msi_entry(entry, pdev) {
> +		if (entry->irq) {
> +			for (i = 0; i < entry->nvec_used; i++) {
> +				hv_teardown_msi_irq_common(pdev, entry, entry->irq +
> i);
> +				irq_domain_free_irqs(entry->irq + i, 1);
> +			}
> +		}
> +	}
> +}
> +
> +/*
> + * IRQ Chip for MSI PCI/PCI-X/PCI-Express Devices,
> + * which implement the MSI or MSI-X Capability Structure.
> + */
> +static struct irq_chip hv_pci_msi_controller = {
> +	.name			= "HV-PCI-MSI",
> +	.irq_unmask		= pci_msi_unmask_irq,
> +	.irq_mask		= pci_msi_mask_irq,
> +	.irq_ack		= irq_chip_ack_parent,
> +	.irq_retrigger		= irq_chip_retrigger_hierarchy,
> +	.irq_compose_msi_msg	= hv_irq_compose_msi_msg,
> +	.irq_set_affinity	= msi_domain_set_affinity,
> +	.flags			= IRQCHIP_SKIP_SET_WAKE,
> +};
> +
> +static struct msi_domain_ops pci_msi_domain_ops = {
> +	.domain_free_irqs	= hv_msi_domain_free_irqs,
> +	.msi_prepare		= pci_msi_prepare,
> +};
> +
> +static struct msi_domain_info hv_pci_msi_domain_info = {
> +	.flags		= MSI_FLAG_USE_DEF_DOM_OPS |
> MSI_FLAG_USE_DEF_CHIP_OPS |
> +			  MSI_FLAG_PCI_MSIX,
> +	.ops		= &pci_msi_domain_ops,
> +	.chip		= &hv_pci_msi_controller,
> +	.handler	= handle_edge_irq,
> +	.handler_name	= "edge",
> +};
> +
> +struct irq_domain * __init hv_create_pci_msi_domain(void)
> +{
> +	struct irq_domain *d = NULL;
> +	struct fwnode_handle *fn;
> +
> +	fn = irq_domain_alloc_named_fwnode("HV-PCI-MSI");
> +	if (fn)
> +		d = pci_msi_create_irq_domain(fn, &hv_pci_msi_domain_info,
> x86_vector_domain);
> +
> +	/* No point in going further if we can't get an irq domain */
> +	BUG_ON(!d);
> +
> +	return d;
> +}
> +
> +#endif /* CONFIG_PCI_MSI */
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index cbee72550a12..ccc849e25d5e 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -261,6 +261,8 @@ static inline void hv_set_msi_entry_from_desc(union hv_msi_entry
> *msi_entry,
>  	msi_entry->data.as_uint32 = msi_desc->msg.data;
>  }
> 
> +struct irq_domain *hv_create_pci_msi_domain(void);
> +
>  #else /* CONFIG_HYPERV */
>  static inline void hyperv_init(void) {}
>  static inline void hyperv_setup_mmu_ops(void) {}
> --
> 2.20.1