[PATCH v6 2/5] PCI: hv: Allow dynamic MSI-X vector allocation

Shradha Gupta
2025-06-11T14:10:17Z

Allow dynamic MSI-X vector allocation for pci_hyperv PCI controller
by adding support for the flag MSI_FLAG_PCI_MSIX_ALLOC_DYN and using
pci_msix_prepare_desc() to prepare the MSI-X descriptors.

Feature support added for both x86 and ARM64

Signed-off-by: Shradha Gupta <shradhagupta@linux.microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Reviewed-by: Saurabh Sengar <ssengar@linux.microsoft.com>
---
Changes in v4:
* use the same prepare_desc() callback for arm and x86
---
Changes in v3:
* Add arm64 support
---
Changes in v2:
* split the patch to keep changes in PCI and pci_hyperv controller
seperate
* replace strings "pci vectors" by "MSI-X vectors"
---
drivers/pci/controller/pci-hyperv.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index ef5d655a0052..86ca041bf74a 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -2119,6 +2119,7 @@ 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 = pci_msix_prepare_desc,
};

/**
@@ -2140,7 +2141,7 @@ 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;
--
2.34.1