Re: [RFC PATCH 1/1] PCI:delay configuration of SRIOV capability

[Don Dutile <ddutile@redhat.com>]

On 12/05/2011 01:17 PM, Jesse Barnes wrote:
> On Sun, 6 Nov 2011 10:33:57 +0800
> Ram Pai<linuxram@us.ibm.com>  wrote:
>
>>        The SRIOV capability, namely page size and total_vfs of a device are
>>        configured during enumeration phase of the device.
>>        This can potentially interfere with the PCI operations of the platform,
>>        if the IOV capability of the device is not enabled.
>>
>>        The following patch postpones the configuration of the IOV capability of the
>>        device to a later point, when the IOV capability is explicitly enabled
>>        by the device driver.
>>
>>        The patch is tested on x86 and power platform.
>>
>>        Signed-off-by: Ram Pai<linuxram@us.ibm.com>
>> ---
>>   drivers/pci/iov.c |    4 ++--
>>   1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
>> index b0446dd..c1a6f5c 100644
>> --- a/drivers/pci/iov.c
>> +++ b/drivers/pci/iov.c
>> @@ -346,6 +346,8 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
>>   			return rc;
>>   	}
>>
>> +	pci_write_config_dword(dev, iov->pos + PCI_SRIOV_SYS_PGSIZE, iov->pgsz);
>> +
>>   	iov->ctrl |= PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE;
>>   	pci_block_user_cfg_access(dev);
>>   	pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
>> @@ -451,7 +453,6 @@ 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, total);
>>   	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))
>> @@ -464,7 +465,6 @@ found:
>>   		return -EIO;
>>
>>   	pgsz&= ~(pgsz - 1);
>> -	pci_write_config_dword(dev, pos + PCI_SRIOV_SYS_PGSIZE, pgsz);
>>
>>   	nres = 0;
>>   	for (i = 0; i<  PCI_SRIOV_NUM_BARS; i++) {
>
> Anyone want to volunteer a tested-by for this one?
>
> Thanks,

I tested this patch along with Ram's other recent patch for SRIOV:
[RFC PATCH 1/1]PCI: defer enablement of SRIOV BARS

With or without this patch, device assignment to a KVM guest
using these patches worked for me.  I used one PF in a quad-function
i350, configuring 2 VFs per i350.  I did 4 assign/deassigns to make
sure multiple enable/disables worked.

So, the patch doesn't correct any error I was seeing,
but it doesn't cause any regression either.

Tested-by: Donald Dutile <ddutile@redhat.com>