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

Shradha Gupta
2025-04-16T15:36:08Z

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

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