Messages in this thread Patch in this message | | | Subject | Re: [PATCH v3 2/7] PCI: Ignore enforced alignment to VF BARs | From | Yongji Xie <> | Date | Fri, 1 Jul 2016 14:40:16 +0800 |
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Hi Gavin,
On 2016/7/1 14:05, Gavin Shan wrote:
> On Fri, Jul 01, 2016 at 01:27:17PM +0800, Yongji Xie wrote: >>> On Thu, Jun 30, 2016 at 06:53:08PM +0800, Yongji Xie wrote: >>>> VF BARs are read-only zeroes according to SRIOV spec, >>>> the normal way(writing BARs) of allocating resources wouldn't >>>> be applied to VFs. The VFs' resources would be allocated >>>> when we enable SR-IOV capability. So we should not try to >>>> reassign alignment after we enable VFs. It's meaningless >>>> and will release the allocated resources which leads to a bug. >>>> >>>> Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com> >>>> --- >>>> drivers/pci/pci.c | 4 ++++ >>>> 1 file changed, 4 insertions(+) >>>> >>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >>>> index be8f72c..6ae02de 100644 >>>> --- a/drivers/pci/pci.c >>>> +++ b/drivers/pci/pci.c >>>> @@ -4822,6 +4822,10 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev) >>>> resource_size_t align, size; >>>> u16 command; >>>> >>>> + /* We should never try to reassign VF's alignment */ >>>> + if (dev->is_virtfn) >>>> + return; >>>> + >>> Yongji, I think it's correct to ignore VF's BARs. Another concern is: >>> it's safe to apply alignment to PF's IOV BARs? Lets have an extreme >>> example here: one PF has 16 VFs; each VF has only one 1KB. It means >>> the only PF IOV BAR is 16KB. I don't see how it works after expanding >>> it to 64KB which is the page size. It might be not a problem on PowerNV >>> platform, but potentially a issue on x86? >> Seems like the alignment would not be applied to IOV BARs because >> pci_reassigndev_resource_alignment() will be called before >> sriov_init(). >> > Correct, thanks for the claim. I guess the alignment applied to PF IOV > BARs should be ignored as well? Anyway, the IOV BARs are retireved from > SRIOV capability. It deserves a comment if you plan to take the change. > Actually, the comment here (for ignoring alignment to VF BARs) can be > improved a bit as well, it'd better why the alignment cannot be applied. >
Do you mean we should ignore PF IOV BARs like this:
--- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4833,7 +4833,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev) command &= ~PCI_COMMAND_MEMORY; pci_write_config_word(dev, PCI_COMMAND, command);
- for (i = 0; i < PCI_BRIDGE_RESOURCES; i++) { + for (i = 0; i <= PCI_ROM_RESOURCE; i++) { r = &dev->resource[i]; if (!(r->flags & IORESOURCE_MEM)) continue; Thanks, Yongji
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