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Date: Wed, 28 Oct 2015 13:43:24 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Alexander Duyck <aduyck@...antis.com>
Cc: bhelgaas@...gle.com, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] iov: Update virtfn_max_buses to validate offset and
stride
On Wed, Oct 28, 2015 at 11:32:16AM -0500, Bjorn Helgaas wrote:
> Hi Alex,
>
> Thanks a lot for cleaning this up. I think this is a great
> improvement over what I did.
>
> On Tue, Oct 27, 2015 at 01:52:15PM -0700, Alexander Duyck wrote:
> > This patch pulls the validation of offset and stride into virtfn_max_buses.
> > The general idea is to validate offset and stride for each possible value
> > of numvfs in addition to still determining the maximum bus value for the
> > VFs.
> >
> > I also reversed the loop as the most likely maximum will be when numvfs is
> > set to total_VFs. In addition this makes it so that we loop down to a
> > value of 0 for numvfs which should be the resting state for the register.
> >
> > Fixes: 8e20e89658f2 ("PCI: Set SR-IOV NumVFs to zero after enumeration")
> > Signed-off-by: Alexander Duyck <aduyck@...antis.com>
>
> I'd like to squash this together with my patch instead of having fixes
> on top of fixes. What do you think of the following? (This applies
> on top of 70675e0b6a1a ("PCI: Don't try to restore VF BARs")).
>
>
> commit c20e11b572c5d4e4f01c86580a133122fbd13cfa
> Author: Alexander Duyck <aduyck@...antis.com>
> Date: Wed Oct 28 10:54:32 2015 -0500
>
> PCI: Set SR-IOV NumVFs to zero after enumeration
>
> The enumeration path should leave NumVFs set to zero. But after
> 4449f079722c ("PCI: Calculate maximum number of buses required for VFs"),
> we call virtfn_max_buses() in the enumeration path, which changes NumVFs.
> This NumVFs change is visible via lspci and sysfs until a driver enables
> SR-IOV.
>
> Iterate from TotalVFs down to zero so NumVFs is zero when we're finished
> computing the maximum number of buses. Validate offset and stride in
> the loop, so we can test it at every possible NumVFs setting. Rename
> virtfn_max_buses() to compute_max_vf_buses() to hint that it does have a
> side effect of updating iov->max_VF_buses.
>
> [bhelgaas: changelog, rename, reverse sense of error path]
> Fixes: 4449f079722c ("PCI: Calculate maximum number of buses required for VFs")
> Based-on-patch-by: Ethan Zhao <ethan.zhao@...cle.com>
> Signed-off-by: Alexander Duyck <aduyck@...antis.com>
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index ee0ebff..120cfb3 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -54,24 +54,33 @@ static inline void pci_iov_set_numvfs(struct pci_dev *dev, int nr_virtfn)
> * The PF consumes one bus number. NumVFs, First VF Offset, and VF Stride
> * determine how many additional bus numbers will be consumed by VFs.
> *
> - * Iterate over all valid NumVFs and calculate the maximum number of bus
> - * numbers that could ever be required.
> + * Iterate over all valid NumVFs, validate offset and stride, and calculate
> + * the maximum number of bus numbers that could ever be required.
> */
> -static inline u8 virtfn_max_buses(struct pci_dev *dev)
> +static int compute_max_vf_buses(struct pci_dev *dev)
> {
> struct pci_sriov *iov = dev->sriov;
> - int nr_virtfn;
> - u8 max = 0;
> + int nr_virtfn = iov->total_VFs;
> int busnr;
>
> - for (nr_virtfn = 1; nr_virtfn <= iov->total_VFs; nr_virtfn++) {
> - pci_iov_set_numvfs(dev, nr_virtfn);
> + pci_iov_set_numvfs(dev, nr_virtfn);
> +
> + while (nr_virtfn--) {
> + if (!iov->offset || !iov->stride)
> + goto err;
I think we have a minor problem here. In sriov_enable(), we return an
error if "nr_virtfn > 1 && !iov->stride", so it's legal for stride to
be zero if NumVF is 1. Here we don't allow that. Sec 3.3.10 says:
Note: VF Stride is unused if NumVFs is 0 or 1. If NumVFs is greater
than 1, VF Stride must not be zero."
So I think we should allow "stride == 0" here when NumVFs is 1.
> +
> busnr = pci_iov_virtfn_bus(dev, nr_virtfn - 1);
I think this loop management is slightly wrong: I don't think we ever
compute busnr for the highest VF because we always decrement nr_virtfn
after calling pci_iov_set_numvfs(), and then we subtract one again.
E.g., if Total VFs is 8, the VFs are numbered VF0..VF7, and we have
this, which doesn't check VF7:
nr_virtfn = iov->total_VFs # nr_virtfn == 8
pci_iov_set_numvfs(..., nr_virtfn) # passes 8 (correct)
while (nr_virtfn--) {
# nr_virtfn == 7 in loop body
pci_iov_virtfn_bus(..., nr_virtfn - 1) # passes 6 (wrong)
> - if (busnr > max)
> - max = busnr;
> + if (busnr > iov->max_VF_buses)
> + iov->max_VF_buses = busnr;
> +
> + pci_iov_set_numvfs(dev, nr_virtfn);
> }
>
> - return max;
> + return 0;
> +
> +err:
> + pci_iov_set_numvfs(dev, 0);
> + return -EIO;
> }
Here's my new proposal:
static int compute_max_vf_buses(struct pci_dev *dev)
{
struct pci_sriov *iov = dev->sriov;
int nr_virtfn, busnr, rc = 0;
for (nr_virtfn = iov->total_VFs; nr_virtfn; nr_virtfn--) {
pci_iov_set_numvfs(dev, nr_virtfn);
if (!iov->offset || (nr_virtfn > 1 && !iov->stride)) {
rc = -EIO;
goto out;
}
busnr = pci_iov_virtfn_bus(dev, nr_virtfn - 1);
if (busnr > iov->max_VF_buses)
iov->max_VF_buses = busnr;
}
out:
pci_iov_set_numvfs(dev, 0);
return rc;
}
--
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