From: Nirmal Patel <nirmal.patel@linux.intel.com>
Date: Tue, 16 Nov 2021 15:11:36 -0700
Subject: PCI: vmd: Clean up domain before enumeration
Git-commit: 6aab5622296b990024ee67dd7efa7d143e7558d0
Patch-mainline: 5.17-rc1
References: jsc#PED-826

During VT-d pass-through, the VMD driver occasionally fails to
enumerate underlying NVMe devices when repetitive reboots are
performed in the guest OS. The issue can be resolved by resetting
VMD root ports for proper enumeration and triggering secondary bus
reset which will also propagate reset through downstream bridges.

Link: https://lore.kernel.org/r/20211116221136.85134-1-nirmal.patel@linux.intel.com
Signed-off-by: Nirmal Patel <nirmal.patel@linux.intel.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Jon Derrick <jonathan.derrick@linux.dev>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/pci/controller/vmd.c |   37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -499,6 +499,40 @@ static inline void vmd_acpi_begin(void)
 static inline void vmd_acpi_end(void) { }
 #endif /* CONFIG_ACPI */
 
+static void vmd_domain_reset(struct vmd_dev *vmd)
+{
+	u16 bus, max_buses = resource_size(&vmd->resources[0]);
+	u8 dev, functions, fn, hdr_type;
+	char __iomem *base;
+
+	for (bus = 0; bus < max_buses; bus++) {
+		for (dev = 0; dev < 32; dev++) {
+			base = vmd->cfgbar + PCIE_ECAM_OFFSET(bus,
+						PCI_DEVFN(dev, 0), 0);
+
+			hdr_type = readb(base + PCI_HEADER_TYPE) &
+					 PCI_HEADER_TYPE_MASK;
+
+			functions = (hdr_type & 0x80) ? 8 : 1;
+			for (fn = 0; fn < functions; fn++) {
+				base = vmd->cfgbar + PCIE_ECAM_OFFSET(bus,
+						PCI_DEVFN(dev, fn), 0);
+
+				hdr_type = readb(base + PCI_HEADER_TYPE) &
+						PCI_HEADER_TYPE_MASK;
+
+				if (hdr_type != PCI_HEADER_TYPE_BRIDGE ||
+				    (readw(base + PCI_CLASS_DEVICE) !=
+				     PCI_CLASS_BRIDGE_PCI))
+					continue;
+
+				memset_io(base + PCI_IO_BASE, 0,
+					  PCI_ROM_ADDRESS1 - PCI_IO_BASE);
+			}
+		}
+	}
+}
+
 static void vmd_attach_resources(struct vmd_dev *vmd)
 {
 	vmd->dev->resource[VMD_MEMBAR1].child = &vmd->resources[1];
@@ -803,6 +837,9 @@ static int vmd_enable_domain(struct vmd_
 	vmd_acpi_begin();
 
 	pci_scan_child_bus(vmd->bus);
+	vmd_domain_reset(vmd);
+	list_for_each_entry(child, &vmd->bus->children, node)
+		pci_reset_bus(child->self);
 	pci_assign_unassigned_bus_resources(vmd->bus);
 
 	/*