Re: [PATCH 1/1] pci/quirks: fix a dmar fault for intel 82599 card

["Li, ZhenHua" <zhen-hual@hp.com>]

Add Joerg to CC list. For it is also related to iommu module.

Joerg,
There was a try for this dmar fault,
	https://lkml.org/lkml/2014/8/18/118

This patch is trying to fix the same thing.


Zhenhua
On 09/30/2014 02:09 PM, Li, Zhen-Hua wrote:
> On a HP system with Intel Corporation 82599 ethernet adapter, when kernel
> crashed and the kdump kernel boots with intel_iommu=on, there may be some
> unexpected DMA requests on this adapter, which will cause DMA Remapping
> faults like:
>      dmar: DRHD: handling fault status reg 102
>      dmar: DMAR:[DMA Read] Request device [41:00.0] fault addr fff81000
>      DMAR:[fault reason 01] Present bit in root entry is clear
>
> Analysis for this bug:
>
> The present bit is set in this function:
>
> static struct context_entry * device_to_context_entry(
> 		struct intel_iommu *iommu, u8 bus, u8 devfn)
> {
>      ......
>                  set_root_present(root);
>      ......
> }
>
> Calling tree:
> ixgbe_open
>      ixgbe_setup_tx_resources
>          intel_alloc_coherent
>              __intel_map_single
>                  domain_context_mapping
>                      domain_context_mapping_one
>                          device_to_context_entry
>
> This means, the present bit in root entry will not be set until the device
>   driver is loaded.
>
> But in the kdump kernel, some hardware device does not know the OS is the
>   second kernel and the drivers should be loaded again, this causes there are
>   some unexpected DMA requsts on this device when it has not been initialized,
>   and then the DMA Remapping errors come.
>
> To fix this DMAR fault, we need to reset the bus that this device on. Reset
>   the device itself does not work.
>
> There also was a discussion:
> https://lkml.org/lkml/2013/5/14/9
>
> Signed-off-by: Li, Zhen-Hua <zhen-hual@hp.com>
> ---
>   drivers/pci/quirks.c | 11 +++++++++++
>   1 file changed, 11 insertions(+)
>
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index 80c2d01..5198af3 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -25,6 +25,7 @@
>   #include <linux/sched.h>
>   #include <linux/ktime.h>
>   #include <asm/dma.h>	/* isa_dma_bridge_buggy */
> +#include <linux/crash_dump.h>
>   #include "pci.h"
>
>   /*
> @@ -3832,3 +3833,13 @@ void pci_dev_specific_enable_acs(struct pci_dev *dev)
>   		}
>   	}
>   }
> +
> +#ifdef CONFIG_CRASH_DUMP
> +void quirk_reset_buggy_devices(struct pci_dev *dev)
> +{
> +	if (unlikely(is_kdump_kernel()))
> +		pci_try_reset_bus(dev->bus);
> +}
> +DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_VENDOR_ID_INTEL, 0x10f8,
> +		PCI_CLASS_NETWORK_ETHERNET, 8, quirk_reset_buggy_devices);
> +#endif
>