[RFC PATCH 2/4] PCI: Add "pci=iommu_passthrough=" parameter for iommu passthrough

[Lu Baolu]

The new parameter takes a list of devices separated by a semicolon.
Each device specified will have its iommu_passthrough bit in struct
device set. This is very similar to the existing 'disable_acs_redir'
parameter.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 .../admin-guide/kernel-parameters.txt         |  5 +++
 drivers/pci/pci.c                             | 34 +++++++++++++++++++
 drivers/pci/pci.h                             |  1 +
 drivers/pci/probe.c                           |  2 ++
 4 files changed, 42 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index ade4e6ec23e0..d3edc2cb6696 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3583,6 +3583,11 @@
 				may put more devices in an IOMMU group.
 		force_floating	[S390] Force usage of floating interrupts.
 		nomio		[S390] Do not use MIO instructions.
+		iommu_passthrough=<pci_dev>[; ...]
+				Specify one or more PCI devices (in the format
+				specified above) separated by semicolons.
+				Each device specified will bypass IOMMU DMA
+				translation.
 
 	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
 			Management.
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 90dbd7c70371..05bf3f4acc36 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -6401,6 +6401,37 @@ void __weak pci_fixup_cardbus(struct pci_bus *bus)
 }
 EXPORT_SYMBOL(pci_fixup_cardbus);
 
+static const char *iommu_passthrough_param;
+bool pci_iommu_passthrough_match(struct pci_dev *dev)
+{
+	int ret = 0;
+	const char *p = iommu_passthrough_param;
+
+	if (!p)
+		return false;
+
+	while (*p) {
+		ret = pci_dev_str_match(dev, p, &p);
+		if (ret < 0) {
+			pr_info_once("PCI: Can't parse iommu_passthrough parameter: %s\n",
+				     iommu_passthrough_param);
+
+			break;
+		} else if (ret == 1) {
+			pci_info(dev, "PCI: IOMMU passthrough\n");
+			return true;
+		}
+
+		if (*p != ';' && *p != ',') {
+			/* End of param or invalid format */
+			break;
+		}
+		p++;
+	}
+
+	return false;
+}
+
 static int __init pci_setup(char *str)
 {
 	while (str) {
@@ -6462,6 +6493,8 @@ static int __init pci_setup(char *str)
 				pci_add_flags(PCI_SCAN_ALL_PCIE_DEVS);
 			} else if (!strncmp(str, "disable_acs_redir=", 18)) {
 				disable_acs_redir_param = str + 18;
+			} else if (!strncmp(str, "iommu_passthrough=", 18)) {
+				iommu_passthrough_param = str + 18;
 			} else {
 				pr_err("PCI: Unknown option `%s'\n", str);
 			}
@@ -6486,6 +6519,7 @@ static int __init pci_realloc_setup_params(void)
 	resource_alignment_param = kstrdup(resource_alignment_param,
 					   GFP_KERNEL);
 	disable_acs_redir_param = kstrdup(disable_acs_redir_param, GFP_KERNEL);
+	iommu_passthrough_param = kstrdup(iommu_passthrough_param, GFP_KERNEL);
 
 	return 0;
 }
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index a0a53bd05a0b..95f6af06aba6 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -288,6 +288,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev);
 void pci_disable_bridge_window(struct pci_dev *dev);
 struct pci_bus *pci_bus_get(struct pci_bus *bus);
 void pci_bus_put(struct pci_bus *bus);
+bool pci_iommu_passthrough_match(struct pci_dev *dev);
 
 /* PCIe link information */
 #define PCIE_SPEED2STR(speed) \
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 512cb4312ddd..4c571ee75621 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2404,6 +2404,8 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 
 	dev->state_saved = false;
 
+	dev->dev.iommu_passthrough = pci_iommu_passthrough_match(dev);
+
 	pci_init_capabilities(dev);
 
 	/*
-- 
2.17.1