Re: [PATCH v2 1/7] PCI: Set SR-IOV NumVFs to zero after enumeration

[Wei Yang <weiyang@linux.vnet.ibm.com>]

On Fri, Oct 30, 2015 at 11:48:21AM +0800, Wei Yang wrote:
>On Thu, Oct 29, 2015 at 05:22:54PM -0500, Bjorn Helgaas wrote:
>>ines: 115
>>
>>From: Alexander Duyck <aduyck@mirantis.com>
>>
>>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@oracle.com>
>>Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
>>Signed-off-by: Bjorn Helgaas <bhelgaas@google.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 0cdb2d1..1b1acc2 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--) {
>
>Hmm... I agree to iterate the nr_virtfn from total_VFs to 0, which keep the
>original logic, before my patch.
>
>
>> 		pci_iov_set_numvfs(dev, nr_virtfn);
>>+		if (!iov->offset || (nr_virtfn > 1 && !iov->stride)) {
>                                     ^^^

After reading the SPEC, I think this code is correct. The original one removed
below may not comply with the SPEC.

>
>Should be this?
>                if (!iov->offset || (iov->total_VFs > 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;
>>@@ -410,11 +415,6 @@ 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;
>>
>
>Original code will return when it found this condition, so that we don't need
>to bother to do those initialization and then fall back.
>
>So I suggest to keep it here.
>
>> 	pci_read_config_word(dev, pos + PCI_SRIOV_TOTAL_VF, &total);
>> 	if (!total)
>>@@ -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;
>
>The dev->sriov is allocated with kzalloc(), seems we forget to release it?
>
>>+	dev->is_physfn = 0;
>> failed:
>> 	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
>> 		res = &dev->resource[i + PCI_IOV_R
>
>-- 
>Richard Yang
>Help you, Help me

-- 
Richard Yang
Help you, Help me