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@xxxxxxxxxxxxxxxxxx> >>>--- >>>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. Thanks, Gavin -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html