[PATCH] Add pci=sriov=[0|1] to enable or disable SRIOV.

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To help debugging, add a kernel parameter, pci=sriov=[0|1], which enables or
disables SRIOV.

Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
Cc: ddutile@xxxxxxxxxx
Cc: bhelgaas@xxxxxxxxxx
---
 Documentation/kernel-parameters.txt |    3 +++
 drivers/pci/iov.c                   |   31 ++++++++++++++++++++++++++++++-
 drivers/pci/pci.c                   |    2 ++
 drivers/pci/pci.h                   |    3 +++
 4 files changed, 38 insertions(+), 1 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 854ed5c..7ad2d32 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2032,6 +2032,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 				on: Turn ECRC on.
 		realloc		reallocate PCI resources if allocations done by BIOS
 				are erroneous.
+		sriov=		[HW]
+				Format: [0|1]
+				Enable or disable SRIOV support in kernel.
 
 	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
 			Management.
diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 42fae47..4a861df 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -408,6 +408,20 @@ static void sriov_disable(struct pci_dev *dev)
 	iov->nr_virtfn = 0;
 }
 
+unsigned int pci_sriov_enabled = 1;
+
+static int __init do_sriov_enable(char *str)
+{
+	get_option(&str, &pci_sriov_enabled);
+	if (!pci_sriov_enabled)
+		printk(KERN_INFO "SRIOV: Disabled\n");
+	else
+		printk(KERN_INFO "SRIOV: Enabled\n");
+
+	return 1;
+}
+__setup("sriov=", do_sriov_enable);
+
 static int sriov_init(struct pci_dev *dev, int pos)
 {
 	int i;
@@ -419,6 +433,12 @@ static int sriov_init(struct pci_dev *dev, int pos)
 	struct resource *res;
 	struct pci_dev *pdev;
 
+	if (!pci_sriov_enabled) {
+		rc = -EPERM;
+		/* in theory no flags should have been set ... */
+		goto failed;
+	}
+
 	if (dev->pcie_type != PCI_EXP_TYPE_RC_END &&
 	    dev->pcie_type != PCI_EXP_TYPE_ENDPOINT)
 		return -ENODEV;
@@ -614,7 +634,10 @@ resource_size_t pci_sriov_resource_alignment(struct pci_dev *dev, int resno)
 	struct resource tmp;
 	enum pci_bar_type type;
 	int reg = pci_iov_resource_bar(dev, resno, &type);
-	
+
+	if (!pci_sriov_enabled)
+		return 0;
+
 	if (!reg)
 		return 0;
 
@@ -667,6 +690,9 @@ int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn)
 {
 	might_sleep();
 
+	if (!pci_sriov_enabled)
+		return -EPERM;
+
 	if (!dev->is_physfn)
 		return -ENODEV;
 
@@ -682,6 +708,9 @@ void pci_disable_sriov(struct pci_dev *dev)
 {
 	might_sleep();
 
+	if (!pci_sriov_enabled)
+		return;
+
 	if (!dev->is_physfn)
 		return;
 
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e9651f0..c6f1d2f 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3576,6 +3576,8 @@ static int __init pci_setup(char *str)
 				pcie_bus_config = PCIE_BUS_PERFORMANCE;
 			} else if (!strncmp(str, "pcie_bus_peer2peer", 18)) {
 				pcie_bus_config = PCIE_BUS_PEER2PEER;
+			} else if (!strncmp(str, "sriov=", 6)) {
+				pci_sriov_enabled = memparse(str + 7, &str);
 			} else {
 				printk(KERN_ERR "PCI: Unknown option `%s'\n",
 						str);
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index b74084e..33f5fce 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -229,6 +229,9 @@ resource_size_t pci_specified_resource_alignment(struct pci_dev *dev);
 extern void pci_disable_bridge_window(struct pci_dev *dev);
 #endif
 
+/* Use "pci=sriov=[0|1]" to enable or disable SRIOV */
+extern unsigned int pci_sriov_enabled;
+
 /* Single Root I/O Virtualization */
 struct pci_sriov {
 	int pos;		/* capability position */
-- 
1.7.1

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