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@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.
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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