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Date: Thu, 29 Oct 2015 11:29:17 +0800
From: ethan zhao <ethan.zhao@...cle.com>
To: Alexander Duyck <alexander.duyck@...il.com>,
Bjorn Helgaas <helgaas@...nel.org>
CC: bhelgaas@...gle.com, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iov: restore NumVFs register to 0 before return from
virtfn_max_buses()
Alex,
On 2015/10/27 23:15, Alexander Duyck wrote:
> On 10/27/2015 02:28 AM, ethan zhao wrote:
>> 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@...cle.com>
>>>>> Tested-by: Sriharsha Yadagudde <sriharsha.devdas@...cle.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@...gle.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@...cle.com>
>>>> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.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 ?
>
> Because pci_iov_set_numvfs will end up resetting offset and stride
> based on the values when it writes the 0 into numvfs. As such
Seems virtfn_max_buses() never call pci_iov_set_numvfs() with 0, so no
need to check it before the last resetting to 0 ?
> testing it after the reset could give you invalid values since offset
> and stride can be 0 when numvfs is 0.
>
> Actually maybe I will go over this and submit a couple patches
> myself. Looking over things it seems like the code has gotten a bit
> silly since virtfn_max_busses looks like it is iterating over VFs and
> that doesn't make much sense when offset and stride are both positive
so far it works at least. :>
Thanks,
Ethan
> values so it should just be a matter of computing the bus of the last VF.
>
> - Alex
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