Date:	Mon, 12 Jan 2015 17:28:18 +0800
From:	"Li, ZhenHua" <zhen-hual@...com>
To:	Baoquan He <bhe@...hat.com>
CC:	dwmw2@...radead.org, indou.takao@...fujitsu.com, joro@...tes.org,
	vgoyal@...hat.com, dyoung@...hat.com,
	iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, kexec@...ts.infradead.org,
	alex.williamson@...hat.com, ddutile@...hat.com,
	ishii.hironobu@...fujitsu.com, bhelgaas@...gle.com,
	doug.hatch@...com, jerry.hoemann@...com, tom.vaden@...com,
	li.zhang6@...com, lisa.mitchell@...com, billsumnerlinux@...il.com,
	rwright@...com, "Li, ZhenHua" <zhen-hual@...com>
Subject: Re: [PATCH v8 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

On 01/12/2015 05:07 PM, Baoquan He wrote:
> On 01/12/15 at 04:00pm, Li, ZhenHua wrote:
>> Comparing to v7, this version adds only a few lines code:
>>
>> In function copy_page_table,
>>
>> +		__iommu_flush_cache(iommu, phys_to_virt(dma_pte_next),
>> +				VTD_PAGE_SIZE);
>
> So this adding fixs the reported dmar fault on Takao's system, right?
I am not sure whether it can fix the dmar fault on Takao's system, but
I hope it can fix.

>
>>
>>
>> On 01/12/2015 03:06 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
>>>      https://lkml.org/lkml/2015/1/6/1166
>>>
>>> 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@...hat.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@...hat.com> helps testing this patchset.
>>> Takao Indoh <indou.takao@...fujitsu.com> gives valuable suggestions.
>>>
>>>    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@...il.com>
>>> Signed-off-by: Li, Zhen-Hua <zhen-hual@...com>
>>> Signed-off-by: Takao Indoh <indou.takao@...fujitsu.com>
>>> Tested-by: Baoquan He <bhe@...hat.com>
>>> ---
>>>   drivers/iommu/intel-iommu.c         | 1054 +++++++++++++++++++++++++++++++++--
>>>   drivers/iommu/intel_irq_remapping.c |  104 +++-
>>>   include/linux/intel-iommu.h         |   18 +
>>>   3 files changed, 1134 insertions(+), 42 deletions(-)
>>>
>>

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