Re: [PATCH v7 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

[Baoquan He]

On 01/07/15 at 01:25pm, Li, ZhenHua wrote:
> It is same as the last one I send to you yesterday.
> 
> The continuous memory that needed for data in this patchset:
> RE: PAGE_SIZE, 4096 Bytes;
> IRTE: 65536 * 16 ; 1M Bytes;
> 
> It should use same memory as the old versions of this patchset. The
> changes for the last version do not need more memory.

Hi Zhenhua,

It was my mistake because I didn't strip the debug info of modules, then
initramfs is bloated very big. Just now I tested the latest version, it
works well and dump is successful. No dmar fault and intr-remap fault
seen any more, good job!

Thanks
Baoquan


> 
> Regards
> Zhenhua
> 
> On 01/07/2015 01:02 PM, Baoquan He wrote:
> >On 01/07/15 at 12:11pm, Li, ZhenHua wrote:
> >>Many thanks to Takao Indoh and Baoquan He, for your testing on more
> >>different systems.
> >>
> >>The calling of flush functions are added to this version.
> >>
> >>The usage of __iommu_flush_cache function :
> >>1. Fixes a dump on Takao's system.
> >>2. Reduces the count of faults on Baoquan's system.
> >
> >I am testing the version you sent to me yesterday afternoon. Is that
> >different with this patchset? I found your patchset man reserve a big
> >contiguous memory region under 896M, this will cause the crashkernel
> >reservation failed when I set crashkernel=320M. The reason I increase
> >the crashkerenl reservation to 320M is 256M is not enough and cause OOM
> >when that patchset is tested.
> >
> >I am checking what happened.
> >
> >
> >Thanks
> >Baoquan
> >
> >>
> >>Regards
> >>Zhenhua
> >>
> >>On 01/07/2015 12:04 PM, 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 and page table, copy data from the
> >>>    old ones that used by the old kernel.
> >>>5. to use different portions of the iova address ranges for the device drivers
> >>>    in the crashdump kernel than the iova ranges that were in-use at the time
> >>>    of the panic.
> >>>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 page 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
> >>>
> >>>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@xxxxxxxxxx]
> >>>           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@xxxxxxxxxx> helps testing this patchset.
> >>>
> >>>   iommu/vt-d: Update iommu_attach_domain() and its callers
> >>>   iommu/vt-d: Items required for kdump
> >>>   iommu/vt-d: Add domain-id functions
> >>>   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
> >>>
> >>>Signed-off-by: Bill Sumner <billsumnerlinux@xxxxxxxxx>
> >>>Signed-off-by: Li, Zhen-Hua <zhen-hual@xxxxxx>
> >>>Signed-off-by: Takao Indoh <indou.takao@xxxxxxxxxxxxxx>
> >>>Tested-by: Baoquan He <bhe@xxxxxxxxxx>
> >>>---
> >>>  drivers/iommu/intel-iommu.c         | 1050 +++++++++++++++++++++++++++++++++--
> >>>  drivers/iommu/intel_irq_remapping.c |  104 +++-
> >>>  include/linux/intel-iommu.h         |   18 +
> >>>  3 files changed, 1130 insertions(+), 42 deletions(-)
> >>>
> >>
> 
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