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SubjectRe: [Intel-wired-lan] [PATCH] PCI: Check/Set ARI capability before setting numVFs
On Thu, Oct 05, 2017 at 04:07:41PM -0500, Bjorn Helgaas wrote:
> On Wed, Oct 04, 2017 at 04:29:14PM -0700, Alexander Duyck wrote:
> > On Wed, Oct 4, 2017 at 4:01 PM, Bjorn Helgaas <helgaas@kernel.org> wrote:
> > > On Wed, Oct 04, 2017 at 08:52:58AM -0700, Tony Nguyen wrote:
> > >> This fixes a bug that can occur if an AER error is encountered while SRIOV
> > >> devices are present.

I applied the patch below with Alex's ack to pci/virtualization for v4.15.

> commit 95594dedd443e42ab0c16b9fba0109e955e7be13
> Author: Tony Nguyen <anthony.l.nguyen@intel.com>
> Date: Wed Oct 4 08:52:58 2017 -0700
>
> PCI: Restore "ARI Capable Hierarchy" before setting numVFs
>
> In the restore path, we previously read PCI_SRIOV_VF_OFFSET and
> PCI_SRIOV_VF_STRIDE before restoring PCI_SRIOV_CTRL_ARI, which
> affects the offset and stride:
>
> pci_restore_state
> pci_restore_iov_state
> sriov_restore_state
> pci_iov_set_numvfs
> pci_read_config_word(... PCI_SRIOV_VF_OFFSET, &iov->offset)
> pci_write_config_word(... PCI_SRIOV_CTRL, iov->ctrl)
>
> The effect is that suspend/resume and AER recovery, which use
> pci_restore_state(), may corrupt iov->offset and iov->stride. The iov
> state is associated with the device, not the driver, so if we reload the
> driver, it will use the the corrupted data, which may cause crashes like
> this:
>
> kernel BUG at drivers/pci/iov.c:157!
> RIP: 0010:pci_iov_add_virtfn+0x2eb/0x350
> Call Trace:
> pci_enable_sriov+0x353/0x440
> ixgbe_pci_sriov_configure+0xd5/0x1f0 [ixgbe]
> sriov_numvfs_store+0xf7/0x170
> dev_attr_store+0x18/0x30
> sysfs_kf_write+0x37/0x40
> kernfs_fop_write+0x120/0x1b0
> vfs_write+0xb5/0x1a0
> SyS_write+0x55/0xc0
>
> The occurs since during AER recovery the ARI Capable Hierarchy bit, which
> can affect the values for First VF Offset and VF Stride, is not set until
> after pci_iov_set_numvfs() is called. This can cause the iov structure to
> be populated with values that are incorrect if the bit is later set.
> Check and set this bit, if needed, before calling pci_iov_set_numvfs() so
> that the values being populated properly take the ARI bit into account.
>
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
> [bhelgaas: changelog, add comment, also clear ARI if necessary]
> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> CC: Alexander Duyck <alexander.h.duyck@intel.com>
> CC: Emil Tantilov <emil.s.tantilov@intel.com>
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index ce24cf235f01..6bacb8995e96 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -498,6 +498,14 @@ static void sriov_restore_state(struct pci_dev *dev)
> if (ctrl & PCI_SRIOV_CTRL_VFE)
> return;
>
> + /*
> + * Restore PCI_SRIOV_CTRL_ARI before pci_iov_set_numvfs() because
> + * it reads offset & stride, which depend on PCI_SRIOV_CTRL_ARI.
> + */
> + ctrl &= ~PCI_SRIOV_CTRL_ARI;
> + ctrl |= iov->ctrl & PCI_SRIOV_CTRL_ARI;
> + pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, ctrl);
> +
> for (i = PCI_IOV_RESOURCES; i <= PCI_IOV_RESOURCE_END; i++)
> pci_update_resource(dev, i);
>

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