Re: [patch V2 18/23] PCI/MSI: Split out irqdomain code

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Dec 06, 2021 at 11:27:52PM +0100, Thomas Gleixner wrote:
> Move the irqdomain specific code into it's own file.

s/it's/its/

> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Tested-by: Juergen Gross <jgross@suse.com>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
>  drivers/pci/msi/Makefile    |    1 
>  drivers/pci/msi/irqdomain.c |  279 ++++++++++++++++++++++++++++++++++++++
>  drivers/pci/msi/legacy.c    |   13 +
>  drivers/pci/msi/msi.c       |  319 +-------------------------------------------
>  drivers/pci/msi/msi.h       |   39 +++++
>  include/linux/msi.h         |   11 -
>  6 files changed, 340 insertions(+), 322 deletions(-)
> 
> --- a/drivers/pci/msi/Makefile
> +++ b/drivers/pci/msi/Makefile
> @@ -3,4 +3,5 @@
>  # Makefile for the PCI/MSI
>  obj-$(CONFIG_PCI)			+= pcidev_msi.o
>  obj-$(CONFIG_PCI_MSI)			+= msi.o
> +obj-$(CONFIG_PCI_MSI_IRQ_DOMAIN)	+= irqdomain.o
>  obj-$(CONFIG_PCI_MSI_ARCH_FALLBACKS)	+= legacy.o
> --- /dev/null
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -0,0 +1,279 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * PCI Message Signaled Interrupt (MSI) - irqdomain support
> + */
> +#include <linux/acpi_iort.h>
> +#include <linux/irqdomain.h>
> +#include <linux/of_irq.h>
> +
> +#include "msi.h"
> +
> +int pci_msi_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
> +{
> +	struct irq_domain *domain;
> +
> +	domain = dev_get_msi_domain(&dev->dev);
> +	if (domain && irq_domain_is_hierarchy(domain))
> +		return msi_domain_alloc_irqs(domain, &dev->dev, nvec);
> +
> +	return pci_msi_legacy_setup_msi_irqs(dev, nvec, type);
> +}
> +
> +void pci_msi_teardown_msi_irqs(struct pci_dev *dev)
> +{
> +	struct irq_domain *domain;
> +
> +	domain = dev_get_msi_domain(&dev->dev);
> +	if (domain && irq_domain_is_hierarchy(domain))
> +		msi_domain_free_irqs(domain, &dev->dev);
> +	else
> +		pci_msi_legacy_teardown_msi_irqs(dev);
> +}
> +
> +/**
> + * pci_msi_domain_write_msg - Helper to write MSI message to PCI config space
> + * @irq_data:	Pointer to interrupt data of the MSI interrupt
> + * @msg:	Pointer to the message
> + */
> +static void pci_msi_domain_write_msg(struct irq_data *irq_data, struct msi_msg *msg)
> +{
> +	struct msi_desc *desc = irq_data_get_msi_desc(irq_data);
> +
> +	/*
> +	 * For MSI-X desc->irq is always equal to irq_data->irq. For
> +	 * MSI only the first interrupt of MULTI MSI passes the test.
> +	 */
> +	if (desc->irq == irq_data->irq)
> +		__pci_write_msi_msg(desc, msg);
> +}
> +
> +/**
> + * pci_msi_domain_calc_hwirq - Generate a unique ID for an MSI source
> + * @desc:	Pointer to the MSI descriptor
> + *
> + * The ID number is only used within the irqdomain.
> + */
> +static irq_hw_number_t pci_msi_domain_calc_hwirq(struct msi_desc *desc)
> +{
> +	struct pci_dev *dev = msi_desc_to_pci_dev(desc);
> +
> +	return (irq_hw_number_t)desc->pci.msi_attrib.entry_nr |
> +		pci_dev_id(dev) << 11 |
> +		(pci_domain_nr(dev->bus) & 0xFFFFFFFF) << 27;
> +}
> +
> +static inline bool pci_msi_desc_is_multi_msi(struct msi_desc *desc)
> +{
> +	return !desc->pci.msi_attrib.is_msix && desc->nvec_used > 1;
> +}
> +
> +/**
> + * pci_msi_domain_check_cap - Verify that @domain supports the capabilities
> + *			      for @dev
> + * @domain:	The interrupt domain to check
> + * @info:	The domain info for verification
> + * @dev:	The device to check
> + *
> + * Returns:
> + *  0 if the functionality is supported
> + *  1 if Multi MSI is requested, but the domain does not support it
> + *  -ENOTSUPP otherwise
> + */
> +int pci_msi_domain_check_cap(struct irq_domain *domain,
> +			     struct msi_domain_info *info, struct device *dev)
> +{
> +	struct msi_desc *desc = first_pci_msi_entry(to_pci_dev(dev));
> +
> +	/* Special handling to support __pci_enable_msi_range() */
> +	if (pci_msi_desc_is_multi_msi(desc) &&
> +	    !(info->flags & MSI_FLAG_MULTI_PCI_MSI))
> +		return 1;
> +	else if (desc->pci.msi_attrib.is_msix && !(info->flags & MSI_FLAG_PCI_MSIX))
> +		return -ENOTSUPP;
> +
> +	return 0;
> +}
> +
> +static int pci_msi_domain_handle_error(struct irq_domain *domain,
> +				       struct msi_desc *desc, int error)
> +{
> +	/* Special handling to support __pci_enable_msi_range() */
> +	if (pci_msi_desc_is_multi_msi(desc) && error == -ENOSPC)
> +		return 1;
> +
> +	return error;
> +}
> +
> +static void pci_msi_domain_set_desc(msi_alloc_info_t *arg,
> +				    struct msi_desc *desc)
> +{
> +	arg->desc = desc;
> +	arg->hwirq = pci_msi_domain_calc_hwirq(desc);
> +}
> +
> +static struct msi_domain_ops pci_msi_domain_ops_default = {
> +	.set_desc	= pci_msi_domain_set_desc,
> +	.msi_check	= pci_msi_domain_check_cap,
> +	.handle_error	= pci_msi_domain_handle_error,
> +};
> +
> +static void pci_msi_domain_update_dom_ops(struct msi_domain_info *info)
> +{
> +	struct msi_domain_ops *ops = info->ops;
> +
> +	if (ops == NULL) {
> +		info->ops = &pci_msi_domain_ops_default;
> +	} else {
> +		if (ops->set_desc == NULL)
> +			ops->set_desc = pci_msi_domain_set_desc;
> +		if (ops->msi_check == NULL)
> +			ops->msi_check = pci_msi_domain_check_cap;
> +		if (ops->handle_error == NULL)
> +			ops->handle_error = pci_msi_domain_handle_error;
> +	}
> +}
> +
> +static void pci_msi_domain_update_chip_ops(struct msi_domain_info *info)
> +{
> +	struct irq_chip *chip = info->chip;
> +
> +	BUG_ON(!chip);
> +	if (!chip->irq_write_msi_msg)
> +		chip->irq_write_msi_msg = pci_msi_domain_write_msg;
> +	if (!chip->irq_mask)
> +		chip->irq_mask = pci_msi_mask_irq;
> +	if (!chip->irq_unmask)
> +		chip->irq_unmask = pci_msi_unmask_irq;
> +}
> +
> +/**
> + * pci_msi_create_irq_domain - Create a MSI interrupt domain
> + * @fwnode:	Optional fwnode of the interrupt controller
> + * @info:	MSI domain info
> + * @parent:	Parent irq domain
> + *
> + * Updates the domain and chip ops and creates a MSI interrupt domain.
> + *
> + * Returns:
> + * A domain pointer or NULL in case of failure.
> + */
> +struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
> +					     struct msi_domain_info *info,
> +					     struct irq_domain *parent)
> +{
> +	struct irq_domain *domain;
> +
> +	if (WARN_ON(info->flags & MSI_FLAG_LEVEL_CAPABLE))
> +		info->flags &= ~MSI_FLAG_LEVEL_CAPABLE;
> +
> +	if (info->flags & MSI_FLAG_USE_DEF_DOM_OPS)
> +		pci_msi_domain_update_dom_ops(info);
> +	if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
> +		pci_msi_domain_update_chip_ops(info);
> +
> +	info->flags |= MSI_FLAG_ACTIVATE_EARLY;
> +	if (IS_ENABLED(CONFIG_GENERIC_IRQ_RESERVATION_MODE))
> +		info->flags |= MSI_FLAG_MUST_REACTIVATE;
> +
> +	/* PCI-MSI is oneshot-safe */
> +	info->chip->flags |= IRQCHIP_ONESHOT_SAFE;
> +
> +	domain = msi_create_irq_domain(fwnode, info, parent);
> +	if (!domain)
> +		return NULL;
> +
> +	irq_domain_update_bus_token(domain, DOMAIN_BUS_PCI_MSI);
> +	return domain;
> +}
> +EXPORT_SYMBOL_GPL(pci_msi_create_irq_domain);
> +
> +/*
> + * Users of the generic MSI infrastructure expect a device to have a single ID,
> + * so with DMA aliases we have to pick the least-worst compromise. Devices with
> + * DMA phantom functions tend to still emit MSIs from the real function number,
> + * so we ignore those and only consider topological aliases where either the
> + * alias device or RID appears on a different bus number. We also make the
> + * reasonable assumption that bridges are walked in an upstream direction (so
> + * the last one seen wins), and the much braver assumption that the most likely
> + * case is that of PCI->PCIe so we should always use the alias RID. This echoes
> + * the logic from intel_irq_remapping's set_msi_sid(), which presumably works
> + * well enough in practice; in the face of the horrible PCIe<->PCI-X conditions
> + * for taking ownership all we can really do is close our eyes and hope...
> + */
> +static int get_msi_id_cb(struct pci_dev *pdev, u16 alias, void *data)
> +{
> +	u32 *pa = data;
> +	u8 bus = PCI_BUS_NUM(*pa);
> +
> +	if (pdev->bus->number != bus || PCI_BUS_NUM(alias) != bus)
> +		*pa = alias;
> +
> +	return 0;
> +}
> +
> +/**
> + * pci_msi_domain_get_msi_rid - Get the MSI requester id (RID)
> + * @domain:	The interrupt domain
> + * @pdev:	The PCI device.
> + *
> + * The RID for a device is formed from the alias, with a firmware
> + * supplied mapping applied
> + *
> + * Returns: The RID.
> + */
> +u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
> +{
> +	struct device_node *of_node;
> +	u32 rid = pci_dev_id(pdev);
> +
> +	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
> +
> +	of_node = irq_domain_get_of_node(domain);
> +	rid = of_node ? of_msi_map_id(&pdev->dev, of_node, rid) :
> +			iort_msi_map_id(&pdev->dev, rid);
> +
> +	return rid;
> +}
> +
> +/**
> + * pci_msi_get_device_domain - Get the MSI domain for a given PCI device
> + * @pdev:	The PCI device
> + *
> + * Use the firmware data to find a device-specific MSI domain
> + * (i.e. not one that is set as a default).
> + *
> + * Returns: The corresponding MSI domain or NULL if none has been found.
> + */
> +struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
> +{
> +	struct irq_domain *dom;
> +	u32 rid = pci_dev_id(pdev);
> +
> +	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
> +	dom = of_msi_map_get_device_domain(&pdev->dev, rid, DOMAIN_BUS_PCI_MSI);
> +	if (!dom)
> +		dom = iort_get_device_domain(&pdev->dev, rid,
> +					     DOMAIN_BUS_PCI_MSI);
> +	return dom;
> +}
> +
> +/**
> + * pci_dev_has_special_msi_domain - Check whether the device is handled by
> + *				    a non-standard PCI-MSI domain
> + * @pdev:	The PCI device to check.
> + *
> + * Returns: True if the device irqdomain or the bus irqdomain is
> + * non-standard PCI/MSI.
> + */
> +bool pci_dev_has_special_msi_domain(struct pci_dev *pdev)
> +{
> +	struct irq_domain *dom = dev_get_msi_domain(&pdev->dev);
> +
> +	if (!dom)
> +		dom = dev_get_msi_domain(&pdev->bus->dev);
> +
> +	if (!dom)
> +		return true;
> +
> +	return dom->bus_token != DOMAIN_BUS_PCI_MSI;
> +}
> --- a/drivers/pci/msi/legacy.c
> +++ b/drivers/pci/msi/legacy.c
> @@ -4,8 +4,7 @@
>   *
>   * Legacy architecture specific setup and teardown mechanism.
>   */
> -#include <linux/msi.h>
> -#include <linux/pci.h>
> +#include "msi.h"
>  
>  /* Arch hooks */
>  int __weak arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc)
> @@ -50,3 +49,13 @@ void __weak arch_teardown_msi_irqs(struc
>  		}
>  	}
>  }
> +
> +int pci_msi_legacy_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
> +{
> +	return arch_setup_msi_irqs(dev, nvec, type);
> +}
> +
> +void pci_msi_legacy_teardown_msi_irqs(struct pci_dev *dev)
> +{
> +	arch_teardown_msi_irqs(dev);
> +}
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -6,64 +6,16 @@
>   * Copyright (C) Tom Long Nguyen (tom.l.nguyen@intel.com)
>   * Copyright (C) 2016 Christoph Hellwig.
>   */
> -
> -#include <linux/acpi_iort.h>
>  #include <linux/err.h>
>  #include <linux/export.h>
>  #include <linux/irq.h>
> -#include <linux/irqdomain.h>
> -#include <linux/msi.h>
> -#include <linux/of_irq.h>
> -#include <linux/pci.h>
>  
>  #include "../pci.h"
> +#include "msi.h"
>  
>  static int pci_msi_enable = 1;
>  int pci_msi_ignore_mask;
>  
> -#define msix_table_size(flags)	((flags & PCI_MSIX_FLAGS_QSIZE) + 1)
> -
> -#ifdef CONFIG_PCI_MSI_IRQ_DOMAIN
> -static int pci_msi_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
> -{
> -	struct irq_domain *domain;
> -
> -	domain = dev_get_msi_domain(&dev->dev);
> -	if (domain && irq_domain_is_hierarchy(domain))
> -		return msi_domain_alloc_irqs(domain, &dev->dev, nvec);
> -
> -	return arch_setup_msi_irqs(dev, nvec, type);
> -}
> -
> -static void pci_msi_teardown_msi_irqs(struct pci_dev *dev)
> -{
> -	struct irq_domain *domain;
> -
> -	domain = dev_get_msi_domain(&dev->dev);
> -	if (domain && irq_domain_is_hierarchy(domain))
> -		msi_domain_free_irqs(domain, &dev->dev);
> -	else
> -		arch_teardown_msi_irqs(dev);
> -}
> -#else
> -#define pci_msi_setup_msi_irqs		arch_setup_msi_irqs
> -#define pci_msi_teardown_msi_irqs	arch_teardown_msi_irqs
> -#endif
> -
> -/*
> - * PCI 2.3 does not specify mask bits for each MSI interrupt.  Attempting to
> - * mask all MSI interrupts by clearing the MSI enable bit does not work
> - * reliably as devices without an INTx disable bit will then generate a
> - * level IRQ which will never be cleared.
> - */
> -static inline __attribute_const__ u32 msi_multi_mask(struct msi_desc *desc)
> -{
> -	/* Don't shift by >= width of type */
> -	if (desc->pci.msi_attrib.multi_cap >= 5)
> -		return 0xffffffff;
> -	return (1 << (1 << desc->pci.msi_attrib.multi_cap)) - 1;
> -}
> -
>  static noinline void pci_msi_update_mask(struct msi_desc *desc, u32 clear, u32 set)
>  {
>  	raw_spinlock_t *lock = &desc->dev->msi_lock;
> @@ -903,23 +855,6 @@ void pci_disable_msix(struct pci_dev *de
>  }
>  EXPORT_SYMBOL(pci_disable_msix);
>  
> -void pci_no_msi(void)
> -{
> -	pci_msi_enable = 0;
> -}
> -
> -/**
> - * pci_msi_enabled - is MSI enabled?
> - *
> - * Returns true if MSI has not been disabled by the command-line option
> - * pci=nomsi.
> - **/
> -int pci_msi_enabled(void)
> -{
> -	return pci_msi_enable;
> -}
> -EXPORT_SYMBOL(pci_msi_enabled);
> -
>  static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
>  				  struct irq_affinity *affd)
>  {
> @@ -1195,253 +1130,19 @@ struct pci_dev *msi_desc_to_pci_dev(stru
>  }
>  EXPORT_SYMBOL(msi_desc_to_pci_dev);
>  
> -#ifdef CONFIG_PCI_MSI_IRQ_DOMAIN
> -/**
> - * pci_msi_domain_write_msg - Helper to write MSI message to PCI config space
> - * @irq_data:	Pointer to interrupt data of the MSI interrupt
> - * @msg:	Pointer to the message
> - */
> -static void pci_msi_domain_write_msg(struct irq_data *irq_data, struct msi_msg *msg)
> -{
> -	struct msi_desc *desc = irq_data_get_msi_desc(irq_data);
> -
> -	/*
> -	 * For MSI-X desc->irq is always equal to irq_data->irq. For
> -	 * MSI only the first interrupt of MULTI MSI passes the test.
> -	 */
> -	if (desc->irq == irq_data->irq)
> -		__pci_write_msi_msg(desc, msg);
> -}
> -
> -/**
> - * pci_msi_domain_calc_hwirq - Generate a unique ID for an MSI source
> - * @desc:	Pointer to the MSI descriptor
> - *
> - * The ID number is only used within the irqdomain.
> - */
> -static irq_hw_number_t pci_msi_domain_calc_hwirq(struct msi_desc *desc)
> -{
> -	struct pci_dev *dev = msi_desc_to_pci_dev(desc);
> -
> -	return (irq_hw_number_t)desc->pci.msi_attrib.entry_nr |
> -		pci_dev_id(dev) << 11 |
> -		(pci_domain_nr(dev->bus) & 0xFFFFFFFF) << 27;
> -}
> -
> -static inline bool pci_msi_desc_is_multi_msi(struct msi_desc *desc)
> -{
> -	return !desc->pci.msi_attrib.is_msix && desc->nvec_used > 1;
> -}
> -
> -/**
> - * pci_msi_domain_check_cap - Verify that @domain supports the capabilities
> - * 			      for @dev
> - * @domain:	The interrupt domain to check
> - * @info:	The domain info for verification
> - * @dev:	The device to check
> - *
> - * Returns:
> - *  0 if the functionality is supported
> - *  1 if Multi MSI is requested, but the domain does not support it
> - *  -ENOTSUPP otherwise
> - */
> -int pci_msi_domain_check_cap(struct irq_domain *domain,
> -			     struct msi_domain_info *info, struct device *dev)
> -{
> -	struct msi_desc *desc = first_pci_msi_entry(to_pci_dev(dev));
> -
> -	/* Special handling to support __pci_enable_msi_range() */
> -	if (pci_msi_desc_is_multi_msi(desc) &&
> -	    !(info->flags & MSI_FLAG_MULTI_PCI_MSI))
> -		return 1;
> -	else if (desc->pci.msi_attrib.is_msix && !(info->flags & MSI_FLAG_PCI_MSIX))
> -		return -ENOTSUPP;
> -
> -	return 0;
> -}
> -
> -static int pci_msi_domain_handle_error(struct irq_domain *domain,
> -				       struct msi_desc *desc, int error)
> -{
> -	/* Special handling to support __pci_enable_msi_range() */
> -	if (pci_msi_desc_is_multi_msi(desc) && error == -ENOSPC)
> -		return 1;
> -
> -	return error;
> -}
> -
> -static void pci_msi_domain_set_desc(msi_alloc_info_t *arg,
> -				    struct msi_desc *desc)
> -{
> -	arg->desc = desc;
> -	arg->hwirq = pci_msi_domain_calc_hwirq(desc);
> -}
> -
> -static struct msi_domain_ops pci_msi_domain_ops_default = {
> -	.set_desc	= pci_msi_domain_set_desc,
> -	.msi_check	= pci_msi_domain_check_cap,
> -	.handle_error	= pci_msi_domain_handle_error,
> -};
> -
> -static void pci_msi_domain_update_dom_ops(struct msi_domain_info *info)
> -{
> -	struct msi_domain_ops *ops = info->ops;
> -
> -	if (ops == NULL) {
> -		info->ops = &pci_msi_domain_ops_default;
> -	} else {
> -		if (ops->set_desc == NULL)
> -			ops->set_desc = pci_msi_domain_set_desc;
> -		if (ops->msi_check == NULL)
> -			ops->msi_check = pci_msi_domain_check_cap;
> -		if (ops->handle_error == NULL)
> -			ops->handle_error = pci_msi_domain_handle_error;
> -	}
> -}
> -
> -static void pci_msi_domain_update_chip_ops(struct msi_domain_info *info)
> -{
> -	struct irq_chip *chip = info->chip;
> -
> -	BUG_ON(!chip);
> -	if (!chip->irq_write_msi_msg)
> -		chip->irq_write_msi_msg = pci_msi_domain_write_msg;
> -	if (!chip->irq_mask)
> -		chip->irq_mask = pci_msi_mask_irq;
> -	if (!chip->irq_unmask)
> -		chip->irq_unmask = pci_msi_unmask_irq;
> -}
> -
> -/**
> - * pci_msi_create_irq_domain - Create a MSI interrupt domain
> - * @fwnode:	Optional fwnode of the interrupt controller
> - * @info:	MSI domain info
> - * @parent:	Parent irq domain
> - *
> - * Updates the domain and chip ops and creates a MSI interrupt domain.
> - *
> - * Returns:
> - * A domain pointer or NULL in case of failure.
> - */
> -struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
> -					     struct msi_domain_info *info,
> -					     struct irq_domain *parent)
> -{
> -	struct irq_domain *domain;
> -
> -	if (WARN_ON(info->flags & MSI_FLAG_LEVEL_CAPABLE))
> -		info->flags &= ~MSI_FLAG_LEVEL_CAPABLE;
> -
> -	if (info->flags & MSI_FLAG_USE_DEF_DOM_OPS)
> -		pci_msi_domain_update_dom_ops(info);
> -	if (info->flags & MSI_FLAG_USE_DEF_CHIP_OPS)
> -		pci_msi_domain_update_chip_ops(info);
> -
> -	info->flags |= MSI_FLAG_ACTIVATE_EARLY;
> -	if (IS_ENABLED(CONFIG_GENERIC_IRQ_RESERVATION_MODE))
> -		info->flags |= MSI_FLAG_MUST_REACTIVATE;
> -
> -	/* PCI-MSI is oneshot-safe */
> -	info->chip->flags |= IRQCHIP_ONESHOT_SAFE;
> -
> -	domain = msi_create_irq_domain(fwnode, info, parent);
> -	if (!domain)
> -		return NULL;
> -
> -	irq_domain_update_bus_token(domain, DOMAIN_BUS_PCI_MSI);
> -	return domain;
> -}
> -EXPORT_SYMBOL_GPL(pci_msi_create_irq_domain);
> -
> -/*
> - * Users of the generic MSI infrastructure expect a device to have a single ID,
> - * so with DMA aliases we have to pick the least-worst compromise. Devices with
> - * DMA phantom functions tend to still emit MSIs from the real function number,
> - * so we ignore those and only consider topological aliases where either the
> - * alias device or RID appears on a different bus number. We also make the
> - * reasonable assumption that bridges are walked in an upstream direction (so
> - * the last one seen wins), and the much braver assumption that the most likely
> - * case is that of PCI->PCIe so we should always use the alias RID. This echoes
> - * the logic from intel_irq_remapping's set_msi_sid(), which presumably works
> - * well enough in practice; in the face of the horrible PCIe<->PCI-X conditions
> - * for taking ownership all we can really do is close our eyes and hope...
> - */
> -static int get_msi_id_cb(struct pci_dev *pdev, u16 alias, void *data)
> -{
> -	u32 *pa = data;
> -	u8 bus = PCI_BUS_NUM(*pa);
> -
> -	if (pdev->bus->number != bus || PCI_BUS_NUM(alias) != bus)
> -		*pa = alias;
> -
> -	return 0;
> -}
> -
> -/**
> - * pci_msi_domain_get_msi_rid - Get the MSI requester id (RID)
> - * @domain:	The interrupt domain
> - * @pdev:	The PCI device.
> - *
> - * The RID for a device is formed from the alias, with a firmware
> - * supplied mapping applied
> - *
> - * Returns: The RID.
> - */
> -u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev)
> -{
> -	struct device_node *of_node;
> -	u32 rid = pci_dev_id(pdev);
> -
> -	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
> -
> -	of_node = irq_domain_get_of_node(domain);
> -	rid = of_node ? of_msi_map_id(&pdev->dev, of_node, rid) :
> -			iort_msi_map_id(&pdev->dev, rid);
> -
> -	return rid;
> -}
> -
> -/**
> - * pci_msi_get_device_domain - Get the MSI domain for a given PCI device
> - * @pdev:	The PCI device
> - *
> - * Use the firmware data to find a device-specific MSI domain
> - * (i.e. not one that is set as a default).
> - *
> - * Returns: The corresponding MSI domain or NULL if none has been found.
> - */
> -struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
> +void pci_no_msi(void)
>  {
> -	struct irq_domain *dom;
> -	u32 rid = pci_dev_id(pdev);
> -
> -	pci_for_each_dma_alias(pdev, get_msi_id_cb, &rid);
> -	dom = of_msi_map_get_device_domain(&pdev->dev, rid, DOMAIN_BUS_PCI_MSI);
> -	if (!dom)
> -		dom = iort_get_device_domain(&pdev->dev, rid,
> -					     DOMAIN_BUS_PCI_MSI);
> -	return dom;
> +	pci_msi_enable = 0;
>  }
>  
>  /**
> - * pci_dev_has_special_msi_domain - Check whether the device is handled by
> - *				    a non-standard PCI-MSI domain
> - * @pdev:	The PCI device to check.
> + * pci_msi_enabled - is MSI enabled?
>   *
> - * Returns: True if the device irqdomain or the bus irqdomain is
> - * non-standard PCI/MSI.
> - */
> -bool pci_dev_has_special_msi_domain(struct pci_dev *pdev)
> + * Returns true if MSI has not been disabled by the command-line option
> + * pci=nomsi.
> + **/
> +int pci_msi_enabled(void)
>  {
> -	struct irq_domain *dom = dev_get_msi_domain(&pdev->dev);
> -
> -	if (!dom)
> -		dom = dev_get_msi_domain(&pdev->bus->dev);
> -
> -	if (!dom)
> -		return true;
> -
> -	return dom->bus_token != DOMAIN_BUS_PCI_MSI;
> +	return pci_msi_enable;
>  }
> -
> -#endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
> +EXPORT_SYMBOL(pci_msi_enabled);
> --- /dev/null
> +++ b/drivers/pci/msi/msi.h
> @@ -0,0 +1,39 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#include <linux/pci.h>
> +#include <linux/msi.h>
> +
> +#define msix_table_size(flags)	((flags & PCI_MSIX_FLAGS_QSIZE) + 1)
> +
> +extern int pci_msi_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
> +extern void pci_msi_teardown_msi_irqs(struct pci_dev *dev);
> +
> +#ifdef CONFIG_PCI_MSI_ARCH_FALLBACKS
> +extern int pci_msi_legacy_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
> +extern void pci_msi_legacy_teardown_msi_irqs(struct pci_dev *dev);
> +#else
> +static inline int pci_msi_legacy_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
> +{
> +	WARN_ON_ONCE(1);
> +	return -ENODEV;
> +}
> +
> +static inline void pci_msi_legacy_teardown_msi_irqs(struct pci_dev *dev)
> +{
> +	WARN_ON_ONCE(1);
> +}
> +#endif
> +
> +/*
> + * PCI 2.3 does not specify mask bits for each MSI interrupt.  Attempting to
> + * mask all MSI interrupts by clearing the MSI enable bit does not work
> + * reliably as devices without an INTx disable bit will then generate a
> + * level IRQ which will never be cleared.
> + */
> +static inline __attribute_const__ u32 msi_multi_mask(struct msi_desc *desc)
> +{
> +	/* Don't shift by >= width of type */
> +	if (desc->pci.msi_attrib.multi_cap >= 5)
> +		return 0xffffffff;
> +	return (1 << (1 << desc->pci.msi_attrib.multi_cap)) - 1;
> +}
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -259,17 +259,6 @@ int arch_setup_msi_irq(struct pci_dev *d
>  void arch_teardown_msi_irq(unsigned int irq);
>  int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
>  void arch_teardown_msi_irqs(struct pci_dev *dev);
> -#else
> -static inline int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
> -{
> -	WARN_ON_ONCE(1);
> -	return -ENODEV;
> -}
> -
> -static inline void arch_teardown_msi_irqs(struct pci_dev *dev)
> -{
> -	WARN_ON_ONCE(1);
> -}
>  #endif
>  
>  /*
>