On Thu, 22 Sep 2016 23:39:01 -0700
Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx> wrote:
> From: Sasha Neftin <sasha.neftin@xxxxxxxxx>
>
> 82579 has a problem reattaching itself after the device is detached.
> The bug was reported by Redhat. The suggested fix is to disable
> FLR capability in PCIe configuration space.
>
> Reproduction:
> Attach the device to a VM, then detach and try to attach again.
>
> Fix:
> Disable FLR capability to prevent the 82579 from hanging.
>
> Signed-off-by: Sasha Neftin <sasha.neftin@xxxxxxxxx>
> Tested-by: Aaron Brown <aaron.f.brown@xxxxxxxxx>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
> ---
> drivers/pci/quirks.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 44e0ff3..59fba6e 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -4431,3 +4431,24 @@ static void quirk_intel_qat_vf_cap(struct pci_dev *pdev)
> }
> }
> DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x443, quirk_intel_qat_vf_cap);
> +/*
> + * Workaround FLR issues for 82579
> + * This code disables the FLR (Function Level Reset) via PCIe, in order
> + * to workaround a bug found while using device passthrough, where the
> + * interface would become non-responsive.
> + * NOTE: the FLR bit is Read/Write Once (RWO) in config space, so if
> + * the BIOS or kernel writes this register * then this workaround will
> + * not work.
> + */
> +static void quirk_intel_flr_cap_dis(struct pci_dev *dev)
> +{
> + int pos = pci_find_capability(dev, PCI_CAP_ID_AF);
> + if (pos) {
> + u8 cap;
> + pci_read_config_byte(dev, pos + PCI_AF_CAP, &cap);
> + cap = cap & (~PCI_AF_CAP_FLR);
> + pci_write_config_byte(dev, pos + PCI_AF_CAP, cap);
> + }
> +}
> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x1502, quirk_intel_flr_cap_dis);
> +DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x1503, quirk_intel_flr_cap_dis);
This seems like a pretty fragile quirk since we're just hoping that the
BIOS hasn't already written this byte. Should we at least re-read and
warn if the write didn't take? What about using dev_flags or a device
specific reset to make this less fragile? A device specific reset
could pick the best reset mechanism for the device, ignoring AF FLR.
Thanks,
Alex
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