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-h...@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
>
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