lkml.org 
[lkml]   [2015]   [Apr]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v10 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel
    On 04/10/15 at 04:42pm, Li, Zhen-Hua wrote:
    > This patchset is an update of Bill Sumner's patchset, implements a fix for:
    > If a kernel boots with intel_iommu=on on a system that supports intel vt-d,
    > when a panic happens, the kdump kernel will boot with these faults:
    >
    > dmar: DRHD: handling fault status reg 102
    > dmar: DMAR:[DMA Read] Request device [01:00.0] fault addr fff80000
    > DMAR:[fault reason 01] Present bit in root entry is clear
    >
    > dmar: DRHD: handling fault status reg 2
    > dmar: INTR-REMAP: Request device [[61:00.0] fault index 42
    > INTR-REMAP:[fault reason 34] Present field in the IRTE entry is clear
    >
    > On some system, the interrupt remapping fault will also happen even if the
    > intel_iommu is not set to on, because the interrupt remapping will be enabled
    > when x2apic is needed by the system.
    >
    > The cause of the DMA fault is described in Bill's original version, and the
    > INTR-Remap fault is caused by a similar reason. In short, the initialization
    > of vt-d drivers causes the in-flight DMA and interrupt requests get wrong
    > response.
    >
    > To fix this problem, we modifies the behaviors of the intel vt-d in the
    > crashdump kernel:
    >
    > For DMA Remapping:
    > 1. To accept the vt-d hardware in an active state,
    > 2. Do not disable and re-enable the translation, keep it enabled.
    > 3. Use the old root entry table, do not rewrite the RTA register.
    > 4. Malloc and use new context entry table, copy data from the old ones that
    > used by the old kernel.
    > 5. Keep using the old page tables before driver is loaded.
    > 6. After device driver is loaded, when it issues the first dma_map command,
    > free the dmar_domain structure for this device, and generate a new one, so
    > that the device can be assigned a new and empty page table.
    > 7. When a new context entry table is generated, we also save its address to
    > the old root entry table.
    >
    > For Interrupt Remapping:
    > 1. To accept the vt-d hardware in an active state,
    > 2. Do not disable and re-enable the interrupt remapping, keep it enabled.
    > 3. Use the old interrupt remapping table, do not rewrite the IRTA register.
    > 4. When ioapic entry is setup, the interrupt remapping table is changed, and
    > the updated data will be stored to the old interrupt remapping table.
    >
    > Advantages of this approach:
    > 1. All manipulation of the IO-device is done by the Linux device-driver
    > for that device.
    > 2. This approach behaves in a manner very similar to operation without an
    > active iommu.
    > 3. Any activity between the IO-device and its RMRR areas is handled by the
    > device-driver in the same manner as during a non-kdump boot.
    > 4. If an IO-device has no driver in the kdump kernel, it is simply left alone.
    > This supports the practice of creating a special kdump kernel without
    > drivers for any devices that are not required for taking a crashdump.
    > 5. Minimal code-changes among the existing mainline intel vt-d code.
    >
    > Summary of changes in this patch set:
    > 1. Added some useful function for root entry table in code intel-iommu.c
    > 2. Added new members to struct root_entry and struct irte;
    > 3. Functions to load old root entry table to iommu->root_entry from the memory
    > of old kernel.
    > 4. Functions to malloc new context entry table and copy the data from the old
    > ones to the malloced new ones.
    > 5. Functions to enable support for DMA remapping in kdump kernel.
    > 6. Functions to load old irte data from the old kernel to the kdump kernel.
    > 7. Some code changes that support other behaviours that have been listed.
    > 8. In the new functions, use physical address as "unsigned long" type, not
    > pointers.
    >
    > Original version by Bill Sumner:
    > https://lkml.org/lkml/2014/1/10/518
    > https://lkml.org/lkml/2014/4/15/716
    > https://lkml.org/lkml/2014/4/24/836
    >
    > Zhenhua's updates:
    > https://lkml.org/lkml/2014/10/21/134
    > https://lkml.org/lkml/2014/12/15/121
    > https://lkml.org/lkml/2014/12/22/53
    > https://lkml.org/lkml/2015/1/6/1166
    > https://lkml.org/lkml/2015/1/12/35
    > https://lkml.org/lkml/2015/3/19/33
    >
    > Changelog[v10]:
    > 1. Do not use CONFIG_CRASH_DUMP and is_kdump_kernel().
    > Use one flag which stores the te and ir status in last kernel:
    > iommu->pre_enabled_trans
    > iommu->pre_enabled_ir
    >
    > Changelog[v9]:
    > 1. Add new function iommu_attach_domain_with_id.
    > 2. Do not copy old page tables, keep using the old ones.
    > 3. Remove functions:
    > intel_iommu_did_to_domain_values_entry
    > intel_iommu_get_dids_from_old_kernel
    > device_to_domain_id
    > copy_page_addr
    > copy_page_table
    > copy_context_entry
    > copy_context_entry_table
    > 4. Add new function device_to_existing_context_entry.
    >
    > Changelog[v8]:
    > 1. Add a missing __iommu_flush_cache in function copy_page_table.
    >
    > Changelog[v7]:
    > 1. Use __iommu_flush_cache to flush the data to hardware.
    >
    > Changelog[v6]:
    > 1. Use "unsigned long" as type of physical address.
    > 2. Use new function unmap_device_dma to unmap the old dma.
    > 3. Some small incorrect bits order for aw shift.
    >
    > Changelog[v5]:
    > 1. Do not disable and re-enable traslation and interrupt remapping.
    > 2. Use old root entry table.
    > 3. Use old interrupt remapping table.
    > 4. New functions to copy data from old kernel, and save to old kernel mem.
    > 5. New functions to save updated root entry table and irte table.
    > 6. Use intel_unmap to unmap the old dma;
    > 7. Allocate new pages while driver is being loaded.
    >
    > Changelog[v4]:
    > 1. Cut off the patches that move some defines and functions to new files.
    > 2. Reduce the numbers of patches to five, make it more easier to read.
    > 3. Changed the name of functions, make them consistent with current context
    > get/set functions.
    > 4. Add change to function __iommu_attach_domain.
    >
    > Changelog[v3]:
    > 1. Commented-out "#define DEBUG 1" to eliminate debug messages.
    > 2. Updated the comments about changes in each version.
    > 3. Fixed: one-line added to Copy-Translations patch to initialize the iovad
    > struct as recommended by Baoquan He [bhe@redhat.com]
    > init_iova_domain(&domain->iovad, DMA_32BIT_PFN);
    >
    > Changelog[v2]:
    > The following series implements a fix for:
    > A kdump problem about DMA that has been discussed for a long time. That is,
    > when a kernel panics and boots into the kdump kernel, DMA started by the
    > panicked kernel is not stopped before the kdump kernel is booted and the
    > kdump kernel disables the IOMMU while this DMA continues. This causes the
    > IOMMU to stop translating the DMA addresses as IOVAs and begin to treat
    > them as physical memory addresses -- which causes the DMA to either:
    > (1) generate DMAR errors or
    > (2) generate PCI SERR errors or
    > (3) transfer data to or from incorrect areas of memory. Often this
    > causes the dump to fail.
    >
    > Changelog[v1]:
    > The original version.
    >
    > Changed in this version:
    > 1. Do not disable and re-enable traslation and interrupt remapping.
    > 2. Use old root entry table.
    > 3. Use old interrupt remapping table.
    > 4. Use "unsigned long" as physical address.
    > 5. Use intel_unmap to unmap the old dma;
    >
    > Baoquan He <bhe@redhat.com> helps testing this patchset.
    > Takao Indoh <indou.takao@jp.fujitsu.com> gives valuable suggestions.
    >
    > Li, Zhen-Hua (10):
    > iommu/vt-d: New function to attach domain with id
    > iommu/vt-d: Items required for kdump
    > iommu/vt-d: Function to get old context entry
    > iommu/vt-d: functions to copy data from old mem
    > iommu/vt-d: Add functions to load and save old re
    > iommu/vt-d: datatypes and functions used for kdump
    > iommu/vt-d: enable kdump support in iommu module
    > iommu/vt-d: assign new page table for dma_map
    > iommu/vt-d: Copy functions for irte
    > iommu/vt-d: Use old irte in kdump kernel
    >
    > drivers/iommu/intel-iommu.c | 518 ++++++++++++++++++++++++++++++++++--
    > drivers/iommu/intel_irq_remapping.c | 96 ++++++-
    > include/linux/intel-iommu.h | 16 ++
    > 3 files changed, 605 insertions(+), 25 deletions(-)
    >
    > --
    > 2.0.0-rc0


    Again, I think it is bad to use old page table, below issues need consider:
    1) make sure old page table are reliable across crash
    2) do not allow writing oldmem after crash

    Please correct me if I'm wrong, or if above is not doable I think I will vote for
    resetting pci bus.

    Thanks
    Dave


    \
     
     \ /
      Last update: 2015-04-15 03:21    [W:2.366 / U:0.012 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site