Re: [PATCH v6 1/5] PCI/MSI: Export pci_msix_prepare_desc() for dynamic MSI-X allocations

Bjorn Helgaas
2025-06-13T22:03:05Z

On Wed, Jun 11, 2025 at 07:10:01AM -0700, Shradha Gupta wrote:
> For supporting dynamic MSI-X vector allocation by PCI controllers, enabling
> the flag MSI_FLAG_PCI_MSIX_ALLOC_DYN is not enough, msix_prepare_msi_desc()
> to prepare the MSI descriptor is also needed.
>
> Export pci_msix_prepare_desc() to allow PCI controllers to support dynamic
> MSI-X vector allocation.
>
> Signed-off-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
> Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>

If you need it; I see you already have a branch at
https://github.com/shradhagupta6/linux/tree/shradha_v6.16-rc1

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

> ---
> drivers/pci/msi/irqdomain.c | 5 +++--
> include/linux/msi.h | 2 ++
> 2 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> index c05152733993..765312c92d9b 100644
> --- a/drivers/pci/msi/irqdomain.c
> +++ b/drivers/pci/msi/irqdomain.c
> @@ -222,13 +222,14 @@ static void pci_irq_unmask_msix(struct irq_data *data)
> pci_msix_unmask(irq_data_get_msi_desc(data));
> }
>
> -static void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
> - struct msi_desc *desc)
> +void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
> + struct msi_desc *desc)
> {
> /* Don't fiddle with preallocated MSI descriptors */
> if (!desc->pci.mask_base)
> msix_prepare_msi_desc(to_pci_dev(desc->dev), desc);
> }
> +EXPORT_SYMBOL_GPL(pci_msix_prepare_desc);
>
> static const struct msi_domain_template pci_msix_template = {
> .chip = {
> diff --git a/include/linux/msi.h b/include/linux/msi.h
> index 6863540f4b71..7f254bde5426 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -706,6 +706,8 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
> struct irq_domain *parent);
> u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev *pdev);
> struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
> +void pci_msix_prepare_desc(struct irq_domain *domain, msi_alloc_info_t *arg,
> + struct msi_desc *desc);
> #else /* CONFIG_PCI_MSI */
> static inline struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev)
> {
> --
> 2.34.1
>