[3.19.y-ckt stable] Patch "PCI: Add dev_flags bit to access VPD through function 0" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    PCI: Add dev_flags bit to access VPD through function 0

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt8.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 71beae2ce73c16b93566f1169e73e50e65c5c850 Mon Sep 17 00:00:00 2001
From: Mark Rustad <mark.d.rustad at intel.com>
Date: Mon, 13 Jul 2015 11:40:02 -0700
Subject: PCI: Add dev_flags bit to access VPD through function 0

commit 932c435caba8a2ce473a91753bad0173269ef334 upstream.

Add a dev_flags bit, PCI_DEV_FLAGS_VPD_REF_F0, to access VPD through
function 0 to provide VPD access on other functions.  This is for hardware
devices that provide copies of the same VPD capability registers in
multiple functions.  Because the kernel expects that each function has its
own registers, both the locking and the state tracking are affected by VPD
accesses to different functions.

On such devices for example, if a VPD write is performed on function 0,
*any* later attempt to read VPD from any other function of that device will
hang.  This has to do with how the kernel tracks the expected value of the
F bit per function.

Concurrent accesses to different functions of the same device can not only
hang but also corrupt both read and write VPD data.

When hangs occur, typically the error message:

  vpd r/w failed.  This is likely a firmware bug on this device.

will be seen.

Never set this bit on function 0 or there will be an infinite recursion.

Signed-off-by: Mark Rustad <mark.d.rustad at intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
Acked-by: Alexander Duyck <alexander.h.duyck at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/pci/access.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 include/linux/pci.h  |  2 ++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index 49dd766..7f249b9 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -352,6 +352,56 @@ static const struct pci_vpd_ops pci_vpd_pci22_ops = {
 	.release = pci_vpd_pci22_release,
 };

+static ssize_t pci_vpd_f0_read(struct pci_dev *dev, loff_t pos, size_t count,
+			       void *arg)
+{
+	struct pci_dev *tdev = pci_get_slot(dev->bus, PCI_SLOT(dev->devfn));
+	ssize_t ret;
+
+	if (!tdev)
+		return -ENODEV;
+
+	ret = pci_read_vpd(tdev, pos, count, arg);
+	pci_dev_put(tdev);
+	return ret;
+}
+
+static ssize_t pci_vpd_f0_write(struct pci_dev *dev, loff_t pos, size_t count,
+				const void *arg)
+{
+	struct pci_dev *tdev = pci_get_slot(dev->bus, PCI_SLOT(dev->devfn));
+	ssize_t ret;
+
+	if (!tdev)
+		return -ENODEV;
+
+	ret = pci_write_vpd(tdev, pos, count, arg);
+	pci_dev_put(tdev);
+	return ret;
+}
+
+static const struct pci_vpd_ops pci_vpd_f0_ops = {
+	.read = pci_vpd_f0_read,
+	.write = pci_vpd_f0_write,
+	.release = pci_vpd_pci22_release,
+};
+
+static int pci_vpd_f0_dev_check(struct pci_dev *dev)
+{
+	struct pci_dev *tdev = pci_get_slot(dev->bus, PCI_SLOT(dev->devfn));
+	int ret = 0;
+
+	if (!tdev)
+		return -ENODEV;
+	if (!tdev->vpd || !tdev->multifunction ||
+	    dev->class != tdev->class || dev->vendor != tdev->vendor ||
+	    dev->device != tdev->device)
+		ret = -ENODEV;
+
+	pci_dev_put(tdev);
+	return ret;
+}
+
 int pci_vpd_pci22_init(struct pci_dev *dev)
 {
 	struct pci_vpd_pci22 *vpd;
@@ -360,12 +410,21 @@ int pci_vpd_pci22_init(struct pci_dev *dev)
 	cap = pci_find_capability(dev, PCI_CAP_ID_VPD);
 	if (!cap)
 		return -ENODEV;
+	if (dev->dev_flags & PCI_DEV_FLAGS_VPD_REF_F0) {
+		int ret = pci_vpd_f0_dev_check(dev);
+
+		if (ret)
+			return ret;
+	}
 	vpd = kzalloc(sizeof(*vpd), GFP_ATOMIC);
 	if (!vpd)
 		return -ENOMEM;

 	vpd->base.len = PCI_VPD_PCI22_SIZE;
-	vpd->base.ops = &pci_vpd_pci22_ops;
+	if (dev->dev_flags & PCI_DEV_FLAGS_VPD_REF_F0)
+		vpd->base.ops = &pci_vpd_f0_ops;
+	else
+		vpd->base.ops = &pci_vpd_pci22_ops;
 	mutex_init(&vpd->lock);
 	vpd->cap = cap;
 	vpd->busy = false;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 03d4863..71e3f7f 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -177,6 +177,8 @@ enum pci_dev_flags {
 	PCI_DEV_FLAG_PCIE_BRIDGE_ALIAS = (__force pci_dev_flags_t) (1 << 5),
 	/* Do not use bus resets for device */
 	PCI_DEV_FLAGS_NO_BUS_RESET = (__force pci_dev_flags_t) (1 << 6),
+	/* Get VPD from function 0 VPD */
+	PCI_DEV_FLAGS_VPD_REF_F0 = (__force pci_dev_flags_t) (1 << 8),
 };

 enum pci_irq_reroute_variant {
--
1.9.1