[RFC v1 1/5] PCI: hv: Create and export hv_build_logical_dev_id()

Yu Zhang
2025-12-09T05:11:41Z

From: Easwar Hariharan <easwar.hariharan@linux.microsoft.com>

Hyper-V uses a logical device ID to identify a PCI endpoint device for
child partitions. This ID will also be required for future hypercalls
used by the Hyper-V IOMMU driver.

Refactor the logic for building this logical device ID into a standalone
helper function and export the interface for wider use.

Signed-off-by: Easwar Hariharan <easwar.hariharan@linux.microsoft.com>
Signed-off-by: Yu Zhang <zhangyu1@linux.microsoft.com>
---
drivers/pci/controller/pci-hyperv.c | 28 ++++++++++++++++++++--------
include/asm-generic/mshyperv.h | 2 ++
2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 146b43981b27..4b82e06b5d93 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -598,15 +598,31 @@ static unsigned int hv_msi_get_int_vector(struct irq_data *data)

#define hv_msi_prepare pci_msi_prepare

+/**
+ * Build a "Device Logical ID" out of this PCI bus's instance GUID and the
+ * function number of the device.
+ */
+u64 hv_build_logical_dev_id(struct pci_dev *pdev)
+{
+ struct pci_bus *pbus = pdev->bus;
+ struct hv_pcibus_device *hbus = container_of(pbus->sysdata,
+ struct hv_pcibus_device, sysdata);
+
+ return (u64)((hbus->hdev->dev_instance.b[5] << 24) |
+ (hbus->hdev->dev_instance.b[4] << 16) |
+ (hbus->hdev->dev_instance.b[7] << 8) |
+ (hbus->hdev->dev_instance.b[6] & 0xf8) |
+ PCI_FUNC(pdev->devfn));
+}
+EXPORT_SYMBOL_GPL(hv_build_logical_dev_id);
+
/**
* hv_irq_retarget_interrupt() - "Unmask" the IRQ by setting its current
* affinity.
* @data: Describes the IRQ
*
* Build new a destination for the MSI and make a hypercall to
- * update the Interrupt Redirection Table. "Device Logical ID"
- * is built out of this PCI bus's instance GUID and the function
- * number of the device.
+ * update the Interrupt Redirection Table.
*/
static void hv_irq_retarget_interrupt(struct irq_data *data)
{
@@ -642,11 +658,7 @@ static void hv_irq_retarget_interrupt(struct irq_data *data)
params->int_entry.source = HV_INTERRUPT_SOURCE_MSI;
params->int_entry.msi_entry.address.as_uint32 = int_desc->address & 0xffffffff;
params->int_entry.msi_entry.data.as_uint32 = int_desc->data;
- params->device_id = (hbus->hdev->dev_instance.b[5] << 24) |
- (hbus->hdev->dev_instance.b[4] << 16) |
- (hbus->hdev->dev_instance.b[7] << 8) |
- (hbus->hdev->dev_instance.b[6] & 0xf8) |
- PCI_FUNC(pdev->devfn);
+ params->device_id = hv_build_logical_dev_id(pdev);
params->int_target.vector = hv_msi_get_int_vector(data);

if (hbus->protocol_version >= PCI_PROTOCOL_VERSION_1_2) {
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 64ba6bc807d9..1a205ed69435 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -71,6 +71,8 @@ extern enum hv_partition_type hv_curr_partition_type;
extern void * __percpu *hyperv_pcpu_input_arg;
extern void * __percpu *hyperv_pcpu_output_arg;

+extern u64 hv_build_logical_dev_id(struct pci_dev *pdev);
+
u64 hv_do_hypercall(u64 control, void *inputaddr, void *outputaddr);
u64 hv_do_fast_hypercall8(u16 control, u64 input8);
u64 hv_do_fast_hypercall16(u16 control, u64 input1, u64 input2);
--
2.49.0