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    SubjectRe: [BUGFIX][PATCH] pci: check for 4k resource_size alignment in sriov_init
    On Wed, 1 Feb 2012 18:32:06 +0530
    Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> wrote:

    > * Ram Pai <linuxram@us.ibm.com> [2012-02-01 14:21:45]:
    >
    > > On Tue, Jan 31, 2012 at 11:14:02PM +0530, Vaidyanathan Srinivasan wrote:
    > > > * 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++) {
    > >
    > >
    > > ACK. I think it is better to revert afd24ece5c76af87f6fc477f2747b83a764f161c.
    >
    > Hi Ram,
    >
    > Thanks for the ack. But afd24ece5c76af87f6fc477f2747b83a764f161c has
    > one more change of moving
    > pci_write_config_word(dev, pos + PCI_SRIOV_NUM_VF, total) to sriov_enable().
    >
    > This change is required so that we set the PCI_SRIOV_NUM_VF only
    > during sriov_enable.
    >
    > So we should not revert the entire commit, we can just add this change.

    So which is it Ram, the ack or the revert? :)

    Having the right page size early seems like the right solution...

    --
    Jesse Barnes, Intel Open Source Technology Center
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