linux-kernel - [RFC v1 1/5] PCI: hv: Create and export hv_build_logical_dev

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Message-ID: <20251209051128.76913-2-zhangyu1@linux.microsoft.com>
Date: Tue,  9 Dec 2025 13:11:24 +0800
From: Yu Zhang <zhangyu1@...ux.microsoft.com>
To: linux-kernel@...r.kernel.org,
	linux-hyperv@...r.kernel.org,
	iommu@...ts.linux.dev,
	linux-pci@...r.kernel.org
Cc: kys@...rosoft.com,
	haiyangz@...rosoft.com,
	wei.liu@...nel.org,
	decui@...rosoft.com,
	lpieralisi@...nel.org,
	kwilczynski@...nel.org,
	mani@...nel.org,
	robh@...nel.org,
	bhelgaas@...gle.com,
	arnd@...db.de,
	joro@...tes.org,
	will@...nel.org,
	robin.murphy@....com,
	easwar.hariharan@...ux.microsoft.com,
	jacob.pan@...ux.microsoft.com,
	nunodasneves@...ux.microsoft.com,
	mrathor@...ux.microsoft.com,
	mhklinux@...look.com,
	peterz@...radead.org,
	linux-arch@...r.kernel.org
Subject: [RFC v1 1/5] PCI: hv: Create and export hv_build_logical_dev_id()

From: Easwar Hariharan <easwar.hariharan@...ux.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@...ux.microsoft.com>
Signed-off-by: Yu Zhang <zhangyu1@...ux.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