[23/33] PCI/MSI: Split MSIX descriptor setup

The upcoming mechanism to allocate MSI-X vectors after enabling MSI-X needs
to share some of the MSI-X descriptor setup.

The regular descriptor setup on enable has the following code flow:

    1) Allocate descriptor
    2) Setup descriptor with PCI specific data
    3) Insert descriptor
    4) Allocate interrupts which in turn scans the inserted
       descriptors

This cannot be easily changed because the PCI/MSI code needs to handle the
legacy architecture specific allocation model and the irq domain model
where quite some domains have the assumption that the above flow is how it
works.

Ideally the code flow should look like this:

   1) Invoke allocation at the MSI core
   2) MSI core allocates descriptor
   3) MSI core calls back into the irq domain which fills in
      the domain specific parts

This could be done for underlying parent MSI domains which support
post-enable allocation/free but that would create significantly different
code pathes for MSI/MSI-X enable.

Though for dynamic allocation which wants to share the allocation code with
the upcoming PCI/IMS support its the right thing to do.

Split the MSIX descriptor setup into the preallocation part which just sets
the index and fills in the horrible hack of virtual IRQs and the real PCI
specific MSI-X setup part which solely depends on the index in the
descriptor. This allows to provide a common dynami allocation interface at
the MSI core level for both PCI/MSI-X and PCI/IMS.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 drivers/pci/msi/msi.c |   72 +++++++++++++++++++++++++++++++-------------------
 drivers/pci/msi/msi.h |    2 +
 2 files changed, 47 insertions(+), 27 deletions(-)

Spelled "MSI-X" elsewhere (subject line).

On Fri, Nov 11, 2022 at 02:58:47PM +0100, Thomas Gleixner wrote:
> The upcoming mechanism to allocate MSI-X vectors after enabling MSI-X needs
> to share some of the MSI-X descriptor setup.
> 
> The regular descriptor setup on enable has the following code flow:
> 
>     1) Allocate descriptor
>     2) Setup descriptor with PCI specific data
>     3) Insert descriptor
>     4) Allocate interrupts which in turn scans the inserted
>        descriptors
> 
> This cannot be easily changed because the PCI/MSI code needs to handle the
> legacy architecture specific allocation model and the irq domain model
> where quite some domains have the assumption that the above flow is how it
> works.
> 
> Ideally the code flow should look like this:
> 
>    1) Invoke allocation at the MSI core
>    2) MSI core allocates descriptor
>    3) MSI core calls back into the irq domain which fills in
>       the domain specific parts
> 
> This could be done for underlying parent MSI domains which support
> post-enable allocation/free but that would create significantly different
> code pathes for MSI/MSI-X enable.
> 
> Though for dynamic allocation which wants to share the allocation code with
> the upcoming PCI/IMS support its the right thing to do.

s/its/it's/

> Split the MSIX descriptor setup into the preallocation part which just sets

MSI-X

> the index and fills in the horrible hack of virtual IRQs and the real PCI
> specific MSI-X setup part which solely depends on the index in the
> descriptor. This allows to provide a common dynami allocation interface at

dynamic

> the MSI core level for both PCI/MSI-X and PCI/IMS.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

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

Typos below.

> ---
>  drivers/pci/msi/msi.c |   72 +++++++++++++++++++++++++++++++-------------------
>  drivers/pci/msi/msi.h |    2 +
>  2 files changed, 47 insertions(+), 27 deletions(-)
> 
> --- a/drivers/pci/msi/msi.c
> +++ b/drivers/pci/msi/msi.c
> @@ -569,34 +569,56 @@ static void __iomem *msix_map_region(str
>  	return ioremap(phys_addr, nr_entries * PCI_MSIX_ENTRY_SIZE);
>  }
>  
> -static int msix_setup_msi_descs(struct pci_dev *dev, void __iomem *base,
> -				struct msix_entry *entries, int nvec,
> -				struct irq_affinity_desc *masks)
> +/**
> + * msix_prepare_msi_desc - Prepare a half initialized MSI descriptor for operation
> + * @dev:	The PCI device for which the descriptor is prepared
> + * @desc:	The MSI descriptor for preparation
> + *
> + * This is seperate from msix_setup_msi_descs() below to handle dynamic

separate

> + * allocations for MSIX after initial enablement.

MSI-X (and again below)

> + * Ideally the whole MSIX setup would work that way, but there is no way to
> + * support this for the legacy arch_setup_msi_irqs() mechanism and for the
> + * fake irq domains like the x86 XEN one. Sigh...
> + *
> + * The descriptor is zeroed and only @desc::msi_index and @desc::affinity
> + * are set. When called from msix_setup_msi_descs() then the is_virtual
> + * attribute is initialized as well.
> + *
> + * Fill in the rest.
> + */
> +void msix_prepare_msi_desc(struct pci_dev *dev, struct msi_desc *desc)
> +{
> +	desc->nvec_used				= 1;
> +	desc->pci.msi_attrib.is_msix		= 1;
> +	desc->pci.msi_attrib.is_64		= 1;
> +	desc->pci.msi_attrib.default_irq	= dev->irq;
> +	desc->pci.mask_base			= dev->msix_base;
> +	desc->pci.msi_attrib.can_mask		= !pci_msi_ignore_mask &&
> +						  !desc->pci.msi_attrib.is_virtual;
> +
> +	if (desc->pci.msi_attrib.can_mask) {
> +		void __iomem *addr = pci_msix_desc_addr(desc);
> +
> +		desc->pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
> +	}
> +}
> +
> +static int msix_setup_msi_descs(struct pci_dev *dev, struct msix_entry *entries,
> +				int nvec, struct irq_affinity_desc *masks)
>  {
>  	int ret = 0, i, vec_count = pci_msix_vec_count(dev);
>  	struct irq_affinity_desc *curmsk;
>  	struct msi_desc desc;
> -	void __iomem *addr;
>  
>  	memset(&desc, 0, sizeof(desc));
>  
> -	desc.nvec_used			= 1;
> -	desc.pci.msi_attrib.is_msix	= 1;
> -	desc.pci.msi_attrib.is_64	= 1;
> -	desc.pci.msi_attrib.default_irq	= dev->irq;
> -	desc.pci.mask_base		= base;
> -
>  	for (i = 0, curmsk = masks; i < nvec; i++, curmsk++) {
>  		desc.msi_index = entries ? entries[i].entry : i;
>  		desc.affinity = masks ? curmsk : NULL;
>  		desc.pci.msi_attrib.is_virtual = desc.msi_index >= vec_count;
> -		desc.pci.msi_attrib.can_mask = !pci_msi_ignore_mask &&
> -					       !desc.pci.msi_attrib.is_virtual;
>  
> -		if (desc.pci.msi_attrib.can_mask) {
> -			addr = pci_msix_desc_addr(&desc);
> -			desc.pci.msix_ctrl = readl(addr + PCI_MSIX_ENTRY_VECTOR_CTRL);
> -		}
> +		msix_prepare_msi_desc(dev, &desc);
>  
>  		ret = msi_insert_msi_desc(&dev->dev, &desc);
>  		if (ret)
> @@ -629,9 +651,8 @@ static void msix_mask_all(void __iomem *
>  		writel(ctrl, base + PCI_MSIX_ENTRY_VECTOR_CTRL);
>  }
>  
> -static int msix_setup_interrupts(struct pci_dev *dev, void __iomem *base,
> -				 struct msix_entry *entries, int nvec,
> -				 struct irq_affinity *affd)
> +static int msix_setup_interrupts(struct pci_dev *dev, struct msix_entry *entries,
> +				 int nvec, struct irq_affinity *affd)
>  {
>  	struct irq_affinity_desc *masks = NULL;
>  	int ret;
> @@ -640,7 +661,7 @@ static int msix_setup_interrupts(struct
>  		masks = irq_create_affinity_masks(nvec, affd);
>  
>  	msi_lock_descs(&dev->dev);
> -	ret = msix_setup_msi_descs(dev, base, entries, nvec, masks);
> +	ret = msix_setup_msi_descs(dev, entries, nvec, masks);
>  	if (ret)
>  		goto out_free;
>  
> @@ -678,7 +699,6 @@ static int msix_setup_interrupts(struct
>  static int msix_capability_init(struct pci_dev *dev, struct msix_entry *entries,
>  				int nvec, struct irq_affinity *affd)
>  {
> -	void __iomem *base;
>  	int ret, tsize;
>  	u16 control;
>  
> @@ -696,15 +716,13 @@ static int msix_capability_init(struct p
>  	pci_read_config_word(dev, dev->msix_cap + PCI_MSIX_FLAGS, &control);
>  	/* Request & Map MSI-X table region */
>  	tsize = msix_table_size(control);
> -	base = msix_map_region(dev, tsize);
> -	if (!base) {
> +	dev->msix_base = msix_map_region(dev, tsize);
> +	if (!dev->msix_base) {
>  		ret = -ENOMEM;
>  		goto out_disable;
>  	}
>  
> -	dev->msix_base = base;
> -
> -	ret = msix_setup_interrupts(dev, base, entries, nvec, affd);
> +	ret = msix_setup_interrupts(dev, entries, nvec, affd);
>  	if (ret)
>  		goto out_disable;
>  
> @@ -719,7 +737,7 @@ static int msix_capability_init(struct p
>  	 * which takes the MSI-X mask bits into account even
>  	 * when MSI-X is disabled, which prevents MSI delivery.
>  	 */
> -	msix_mask_all(base, tsize);
> +	msix_mask_all(dev->msix_base, tsize);
>  	pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0);
>  
>  	pcibios_free_irq(dev);
> --- a/drivers/pci/msi/msi.h
> +++ b/drivers/pci/msi/msi.h
> @@ -84,6 +84,8 @@ static inline __attribute_const__ u32 ms
>  	return (1 << (1 << desc->pci.msi_attrib.multi_cap)) - 1;
>  }
>  
> +void msix_prepare_msi_desc(struct pci_dev *dev, struct msi_desc *desc);
> +
>  /* Subsystem variables */
>  extern int pci_msi_enable;
>  
>