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SubjectRe: [PATCH v2] iov: restore NumVFs register to 0 before return from virtfn_max_buses()
Alexander,
On 2015/10/27 13:48, Alexander Duyck wrote:
> On 10/15/2015 10:16 AM, Bjorn Helgaas wrote:
>> Hi Ethan,
>>
>> On Wed, Sep 16, 2015 at 12:19:53PM +0900, Ethan Zhao wrote:
>>> After commit 4449f079722c ("PCI: Calculate maximum number of buses
>>> required for VFs"),the initial value of NumVFs register was left to
>>> non-zero after sriov_init() and no VFs was enabled in device driver.
>>> this changed the behaviour of kernel exported by lspci and sysfs etc.
>>> so this patch restore the NumVFs register to zero after the
>>> calculation of max_VF_buses was done and before return from
>>> virtfn_max_buses().
>>>
>>> Tested on stable 4.1 and passed building on stable 4.3-rc1
>>>
>>> Signed-off-by: Ethan Zhao <ethan.zhao@oracle.com>
>>> Tested-by: Sriharsha Yadagudde <sriharsha.devdas@oracle.com>
>> Can you test the patch below? I'm trying to avoid touching
>> PCI_SRIOV_NUM_VF in more than one place, and I think it's OK to set it
>> and test offset/stride at the end, instead of setting NUM_VF to zero,
>> testing offset/stride, computing max_bus, then setting NUM_VF to zero
>> again.
>>
>> Bjorn
>>
>>
>> commit 8e20e89658f23b8d16b1e21810e9f63c8625129c
>> Author: Bjorn Helgaas <bhelgaas@google.com>
>> Date: Thu Oct 15 11:31:21 2015 -0500
>>
>> PCI: Set SR-IOV NumVFs to zero after enumeration
>> 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.
>> Set NumVFs to zero after virtfn_max_buses() computes the
>> maximum number of
>> buses.
>> Fixes: 4449f079722c ("PCI: Calculate maximum number of
>> buses required for VFs")
>> Based-on-patch-by: Ethan Zhao <ethan.zhao@oracle.com>
>> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>>
>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
>> index ee0ebff..0202ab0 100644
>> --- a/drivers/pci/iov.c
>> +++ b/drivers/pci/iov.c
>> @@ -384,7 +384,7 @@ 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 +414,6 @@ 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 +451,6 @@ 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);
>> @@ -475,6 +468,11 @@ found:
>> dev->sriov = iov;
>> dev->is_physfn = 1;
>> iov->max_VF_buses = virtfn_max_buses(dev);
>> + pci_iov_set_numvfs(dev, 0);
>> + if (!iov->offset || (total > 1 && !iov->stride)) {
>> + rc = -EIO;
>> + goto failed;
>> + }
>> return 0;
>
> You might want to reorder this a bit. The problem is offset and
> stride can be 0 if numvfs is 0. So you should probably test offset
> and stride
Yes, the spec says "Note: First VF Offset is unused if NumVFs is 0. If
NumVFs is greater than 0, First VF Offset must
25 not be zero. "
> first, and then reset numvfs to 0.
Why test it before reset numvfs ?

Thanks,
Ethan
>
> - Alex
>



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