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SubjectRe: [BUGFIX][PATCH] pci: check for 4k resource_size alignment in sriov_init
* Ram Pai <linuxram@us.ibm.com> [2012-01-30 11:18:45]:

> On Sat, Jan 28, 2012 at 12:40:32AM +0530, Vaidyanathan Srinivasan wrote:
> > Hi Ram and Jesse,
> >
> > I found a trivial issue with page size alignment check on IBM POWER
> > box with 64k base page size. In sriov_init(), changing the check from
> > PAGE_SIZE (arch and config dependent) to HW_PAGE_SIZE (always 4k) was
> > required to use one of the sriov adapter as PF since the
> > resource_size() comes up as 0x8000 and PAGE_SIZE would be 0x10000 for
> > pseries boxes.
> >
> > I think resource_size() could be less than SystemPageSize, but I would
> > like your comments/ack/nack on any consequences of checking for only
> > 4k alignment here in a system with larger base page size.
>
> As per the SRIOV specs, the resource has to be System page size aligned.
>
> PFs are required to support 4-KB, 8-KB, 64-KB, 256-KB, 1-MB, and 4-MB
> page sizes. In your case if your adapter's PF is not supporting 64K page size
> then I think it is not conforming to the PCI SRIOV spec.

Hi Ram,

Thanks for the pointer. I did some more experiments and found that
the card does support 64k page size, but the PCI_SRIOV_SYS_PGSIZE was
set to default 4k when we do the query and check resource_size().

You were correct, the resource_size() has to come up with 64k on 64k
PAGE_SIZE system. We should not change that check. I was able to
get a working solution by setting PCI_SRIOV_SYS_PGSIZE to 64k before
we do the query.

This was the case in the original code before you moved these to
sriov_enable(). If it is ok to leave the SYS_PGSIZE setting in
sriov_init(), then I have the following fix that works for me.

Please review and let me know your comments.

Thanks,
Vaidy
---
pci: set pci sriov page size before reading sriov bar

For an SRIOV device, PCI_SRIOV_SYS_PGSIZE should be set before
the PCI_SRIOV_BAR is queried. The sys pagesize defaults to 4k,
so this change is required on powerpc box with 64k base page size.

This is a regression caused due to moving SRIOV init to sriov_enable().

| commit afd24ece5c76af87f6fc477f2747b83a764f161c
| Author: Ram Pai <linuxram@us.ibm.com>
| PCI: delay configuration of SRIOV capability
| 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.
Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 0321fa3..0dab5ec 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -347,8 +347,6 @@ 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_cfg_access_lock(dev);
pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
@@ -466,6 +464,7 @@ 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++) {


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