Date:	Wed, 7 Jan 2015 13:02:47 +0800
From:	Baoquan He <bhe@...hat.com>
To:	"Li, ZhenHua" <zhen-hual@...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
Subject: Re: [PATCH v7 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

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@...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.
> >
> >   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         | 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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