PCI: hv: Add a Hyper-V PCI interface driver for software backchannel interface

This interface driver is a helper driver allows other drivers to
have a common interface with the Hyper-V PCI frontend driver.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/pci/controller/Kconfig

@@ -281,5 +281,12 @@ config VMD
 	  To compile this driver as a module, choose M here: the
 	  module will be called vmd.
 
+config PCI_HYPERV_INTERFACE
+	tristate "Hyper-V PCI Interface"
+	depends on X86 && HYPERV && PCI_MSI && PCI_MSI_IRQ_DOMAIN && X86_64
+	help
+	  The Hyper-V PCI Interface is a helper driver allows other drivers to
+	  have a common interface with the Hyper-V PCI frontend driver.
+
 source "drivers/pci/controller/dwc/Kconfig"
 endmenu

drivers/pci/controller/Makefile

@@ -4,6 +4,7 @@ obj-$(CONFIG_PCIE_CADENCE_HOST) += pcie-cadence-host.o
 obj-$(CONFIG_PCIE_CADENCE_EP) += pcie-cadence-ep.o
 obj-$(CONFIG_PCI_FTPCI100) += pci-ftpci100.o
 obj-$(CONFIG_PCI_HYPERV) += pci-hyperv.o
+obj-$(CONFIG_PCI_HYPERV_INTERFACE) += pci-hyperv-intf.o
 obj-$(CONFIG_PCI_MVEBU) += pci-mvebu.o
 obj-$(CONFIG_PCI_AARDVARK) += pci-aardvark.o
 obj-$(CONFIG_PCI_TEGRA) += pci-tegra.o

drivers/pci/controller/pci-hyperv-intf.c

@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) Microsoft Corporation.
+ *
+ * Author:
+ *   Haiyang Zhang <haiyangz@microsoft.com>
+ *
+ * This small module is a helper driver allows other drivers to
+ * have a common interface with the Hyper-V PCI frontend driver.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/hyperv.h>
+
+struct hyperv_pci_block_ops hvpci_block_ops;
+EXPORT_SYMBOL_GPL(hvpci_block_ops);
+
+int hyperv_read_cfg_blk(struct pci_dev *dev, void *buf, unsigned int buf_len,
+			unsigned int block_id, unsigned int *bytes_returned)
+{
+	if (!hvpci_block_ops.read_block)
+		return -EOPNOTSUPP;
+
+	return hvpci_block_ops.read_block(dev, buf, buf_len, block_id,
+					  bytes_returned);
+}
+EXPORT_SYMBOL_GPL(hyperv_read_cfg_blk);
+
+int hyperv_write_cfg_blk(struct pci_dev *dev, void *buf, unsigned int len,
+			 unsigned int block_id)
+{
+	if (!hvpci_block_ops.write_block)
+		return -EOPNOTSUPP;
+
+	return hvpci_block_ops.write_block(dev, buf, len, block_id);
+}
+EXPORT_SYMBOL_GPL(hyperv_write_cfg_blk);
+
+int hyperv_reg_block_invalidate(struct pci_dev *dev, void *context,
+				void (*block_invalidate)(void *context,
+							 u64 block_mask))
+{
+	if (!hvpci_block_ops.reg_blk_invalidate)
+		return -EOPNOTSUPP;
+
+	return hvpci_block_ops.reg_blk_invalidate(dev, context,
+						  block_invalidate);
+}
+EXPORT_SYMBOL_GPL(hyperv_reg_block_invalidate);
+
+static void __exit exit_hv_pci_intf(void)
+{
+}
+
+static int __init init_hv_pci_intf(void)
+{
+	return 0;
+}
+
+module_init(init_hv_pci_intf);
+module_exit(exit_hv_pci_intf);
+
+MODULE_DESCRIPTION("Hyper-V PCI Interface");
+MODULE_LICENSE("GPL v2");

drivers/pci/controller/pci-hyperv.c

@@ -983,7 +983,6 @@ int hv_read_config_block(struct pci_dev *pdev, void *buf, unsigned int len,
 	*bytes_returned = comp_pkt.bytes_returned;
 	return 0;
 }
-EXPORT_SYMBOL(hv_read_config_block);
 
 /**
  * hv_pci_write_config_compl() - Invoked when a response packet for a write
@@ -1070,7 +1069,6 @@ int hv_write_config_block(struct pci_dev *pdev, void *buf, unsigned int len,
 
 	return 0;
 }
-EXPORT_SYMBOL(hv_write_config_block);
 
 /**
  * hv_register_block_invalidate() - Invoked when a config block invalidation
@@ -1101,7 +1099,6 @@ int hv_register_block_invalidate(struct pci_dev *pdev, void *context,
 	return 0;
 
 }
-EXPORT_SYMBOL(hv_register_block_invalidate);
 
 /* Interrupt management hooks */
 static void hv_int_desc_free(struct hv_pci_dev *hpdev,
@@ -3045,10 +3042,19 @@ static struct hv_driver hv_pci_drv = {
 static void __exit exit_hv_pci_drv(void)
 {
 	vmbus_driver_unregister(&hv_pci_drv);
+
+	hvpci_block_ops.read_block = NULL;
+	hvpci_block_ops.write_block = NULL;
+	hvpci_block_ops.reg_blk_invalidate = NULL;
 }
 
 static int __init init_hv_pci_drv(void)
 {
+	/* Initialize PCI block r/w interface */
+	hvpci_block_ops.read_block = hv_read_config_block;
+	hvpci_block_ops.write_block = hv_write_config_block;
+	hvpci_block_ops.reg_blk_invalidate = hv_register_block_invalidate;
+
 	return vmbus_driver_register(&hv_pci_drv);
 }