[4.2.y-ckt stable] Patch "PCI: Set SR-IOV NumVFs to zero after enumeration" 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: Set SR-IOV NumVFs to zero after enumeration

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt1.

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

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From d152e77fede416b0fefe72aa5246a6e255a29110 Mon Sep 17 00:00:00 2001
From: Alexander Duyck <aduyck at mirantis.com>
Date: Thu, 29 Oct 2015 16:20:50 -0500
Subject: PCI: Set SR-IOV NumVFs to zero after enumeration

commit ea9a8854161d9580cfabe011c0ae296ecc0e1d4f upstream.

The enumeration path should leave NumVFs set to zero.  But after
4449f079722c ("PCI: Calculate maximum number of buses required for VFs"),
we call virtfn_max_buses() in the enumeration path, which changes NumVFs.
This NumVFs change is visible via lspci and sysfs until a driver enables
SR-IOV.

Iterate from TotalVFs down to zero so NumVFs is zero when we're finished
computing the maximum number of buses.  Validate offset and stride in
the loop, so we can test it at every possible NumVFs setting.  Rename
virtfn_max_buses() to compute_max_vf_buses() to hint that it does have a
side effect of updating iov->max_VF_buses.

[bhelgaas: changelog, rename, allow numVF==1 && stride==0, rework loop,
reverse sense of error path]
Fixes: 4449f079722c ("PCI: Calculate maximum number of buses required for VFs")
Based-on-patch-by: Ethan Zhao <ethan.zhao at oracle.com>
Signed-off-by: Alexander Duyck <aduyck at mirantis.com>
Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>

Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/pci/iov.c | 41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index ee0ebff..1eadc74 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -54,24 +54,29 @@ static inline void pci_iov_set_numvfs(struct pci_dev *dev, int nr_virtfn)
  * The PF consumes one bus number.  NumVFs, First VF Offset, and VF Stride
  * determine how many additional bus numbers will be consumed by VFs.
  *
- * Iterate over all valid NumVFs and calculate the maximum number of bus
- * numbers that could ever be required.
+ * Iterate over all valid NumVFs, validate offset and stride, and calculate
+ * the maximum number of bus numbers that could ever be required.
  */
-static inline u8 virtfn_max_buses(struct pci_dev *dev)
+static int compute_max_vf_buses(struct pci_dev *dev)
 {
 	struct pci_sriov *iov = dev->sriov;
-	int nr_virtfn;
-	u8 max = 0;
-	int busnr;
+	int nr_virtfn, busnr, rc = 0;

-	for (nr_virtfn = 1; nr_virtfn <= iov->total_VFs; nr_virtfn++) {
+	for (nr_virtfn = iov->total_VFs; nr_virtfn; nr_virtfn--) {
 		pci_iov_set_numvfs(dev, nr_virtfn);
+		if (!iov->offset || (nr_virtfn > 1 && !iov->stride)) {
+			rc = -EIO;
+			goto out;
+		}
+
 		busnr = pci_iov_virtfn_bus(dev, nr_virtfn - 1);
-		if (busnr > max)
-			max = busnr;
+		if (busnr > iov->max_VF_buses)
+			iov->max_VF_buses = busnr;
 	}

-	return max;
+out:
+	pci_iov_set_numvfs(dev, 0);
+	return rc;
 }

 static struct pci_bus *virtfn_add_bus(struct pci_bus *bus, int busnr)
@@ -384,7 +389,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
 	int rc;
 	int nres;
 	u32 pgsz;
-	u16 ctrl, total, offset, stride;
+	u16 ctrl, total;
 	struct pci_sriov *iov;
 	struct resource *res;
 	struct pci_dev *pdev;
@@ -414,11 +419,6 @@ static int sriov_init(struct pci_dev *dev, int pos)

 found:
 	pci_write_config_word(dev, pos + PCI_SRIOV_CTRL, ctrl);
-	pci_write_config_word(dev, pos + PCI_SRIOV_NUM_VF, 0);
-	pci_read_config_word(dev, pos + PCI_SRIOV_VF_OFFSET, &offset);
-	pci_read_config_word(dev, pos + PCI_SRIOV_VF_STRIDE, &stride);
-	if (!offset || (total > 1 && !stride))
-		return -EIO;

 	pci_read_config_dword(dev, pos + PCI_SRIOV_SUP_PGSIZE, &pgsz);
 	i = PAGE_SHIFT > 12 ? PAGE_SHIFT - 12 : 0;
@@ -456,8 +456,6 @@ found:
 	iov->nres = nres;
 	iov->ctrl = ctrl;
 	iov->total_VFs = total;
-	iov->offset = offset;
-	iov->stride = stride;
 	iov->pgsz = pgsz;
 	iov->self = dev;
 	pci_read_config_dword(dev, pos + PCI_SRIOV_CAP, &iov->cap);
@@ -474,10 +472,15 @@ found:

 	dev->sriov = iov;
 	dev->is_physfn = 1;
-	iov->max_VF_buses = virtfn_max_buses(dev);
+	rc = compute_max_vf_buses(dev);
+	if (rc)
+		goto fail_max_buses;

 	return 0;

+fail_max_buses:
+	dev->sriov = NULL;
+	dev->is_physfn = 0;
 failed:
 	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
 		res = &dev->resource[i + PCI_IOV_RESOURCES];
--
1.9.1