Re: [PATCH 1/2] PCI: hv: enable pci_hyperv to allow dynamic vector allocation

Bjorn Helgaas
2025-04-16T18:30:44Z

[+to Thomas]

On Wed, Apr 16, 2025 at 08:36:06AM -0700, Shradha Gupta wrote:
> For supporting dynamic MSI vector allocation by pci controllers, enabling
> the flag MSI_FLAG_PCI_MSIX_ALLOC_DYN is not enough, msix_prepare_msi_desc()
> to prepare the desc is needed. Export pci_msix_prepare_desc() to allow pci
> controllers like pci-hyperv to support dynamic MSI vector allocation.
> Also, add the flag MSI_FLAG_PCI_MSIX_ALLOC_DYN and use
> pci_msix_prepare_desc() in pci_hyperv controller

Follow capitalization convention for subject line. Probably remove
"pci_hyperv" since it already contains "PCI: hv" and add something
about MSI-X.

s/pci/PCI/

s/MSI vector/MSI-X vector/ since the context says you're concerned
with MSI-X.

This requires an ack from Thomas; moved him to "To:" line.

> Signed-off-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
> Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
> Reviewed-by: Long Li <longli@microsoft.com>
> ---
> drivers/pci/controller/pci-hyperv.c | 7 +++++--
> drivers/pci/msi/irqdomain.c | 5 +++--
> include/linux/msi.h | 2 ++
> 3 files changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
> index ac27bda5ba26..f2fa6bdb6bb8 100644
> --- a/drivers/pci/controller/pci-hyperv.c
> +++ b/drivers/pci/controller/pci-hyperv.c
> @@ -598,7 +598,8 @@ static unsigned int hv_msi_get_int_vector(struct irq_data *data)
> return cfg->vector;
> }
>
> -#define hv_msi_prepare pci_msi_prepare
> +#define hv_msi_prepare pci_msi_prepare
> +#define hv_msix_prepare_desc pci_msix_prepare_desc
>
> /**
> * hv_arch_irq_unmask() - "Unmask" the IRQ by setting its current
> @@ -727,6 +728,7 @@ static void hv_arch_irq_unmask(struct irq_data *data)
> #define FLOW_HANDLER NULL
> #define FLOW_NAME NULL
> #define hv_msi_prepare NULL
> +#define hv_msix_prepare_desc NULL
>
> struct hv_pci_chip_data {
> DECLARE_BITMAP(spi_map, HV_PCI_MSI_SPI_NR);
> @@ -2063,6 +2065,7 @@ static struct irq_chip hv_msi_irq_chip = {
> static struct msi_domain_ops hv_msi_ops = {
> .msi_prepare = hv_msi_prepare,
> .msi_free = hv_msi_free,
> + .prepare_desc = hv_msix_prepare_desc,
> };
>
> /**
> @@ -2084,7 +2087,7 @@ static int hv_pcie_init_irq_domain(struct hv_pcibus_device *hbus)
> hbus->msi_info.ops = &hv_msi_ops;
> hbus->msi_info.flags = (MSI_FLAG_USE_DEF_DOM_OPS |
> MSI_FLAG_USE_DEF_CHIP_OPS | MSI_FLAG_MULTI_PCI_MSI |
> - MSI_FLAG_PCI_MSIX);
> + MSI_FLAG_PCI_MSIX | MSI_FLAG_PCI_MSIX_ALLOC_DYN);
> hbus->msi_info.handler = FLOW_HANDLER;
> hbus->msi_info.handler_name = FLOW_NAME;
> hbus->msi_info.data = hbus;
> diff --git a/drivers/pci/msi/irqdomain.c b/drivers/pci/msi/irqdomain.c
> index d7ba8795d60f..43129aa6d6c7 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 86e42742fd0f..d5864d5e75c2 100644
> --- a/include/linux/msi.h
> +++ b/include/linux/msi.h
> @@ -691,6 +691,8 @@ 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
>