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@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. > Takao Indoh <indou.takao@xxxxxxxxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
