Re: [PATCH v3 2/7] PCI: Ignore enforced alignment to VF BARs
From: Gavin Shan <hidden>
Date: 2016-07-01 00:40:11
Also in:
linux-pci, lkml
On Thu, Jun 30, 2016 at 06:53:08PM +0800, Yongji Xie wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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?
/* check if specified PCI is target device to reassign */ align = pci_specified_resource_alignment(dev); if (!align)
Thanks, Gavin