On Tue, 2013-12-03 at 12:41 -0700, Bill Sumner wrote: > 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. I didn't review the content, but please add commit logs per patch. You have a very thorough description here in the cover letter, but the cover letter doesn't get stored in the code base. Thanks, Alex > > This patch set modifies the behavior of the iommu in the (new) crashdump kernel: > 1. to accept the iommu hardware in an active state, > 2. to leave the current translations in-place so that legacy DMA will continue > using its current buffers until the device drivers in the crashdump kernel > initialize and initialize their devices, > 3. 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. > > 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. > > Changes since the RFC version of this patch: > 1. Consolidated all of the operational code into the "copy..." functions. > The "process..." functions were primarily used for diagnostics and > exploration; however, there was a small amount of operational code that > used the "process..." functions. > This operational code has been moved into the "copy..." functions. > > 2. Removed the "Process ..." functions and the diagnostic code that ran > on that function set. This removed about 1/4 of the code -- which this > operational patch set no longer needs. These portions of the RFC patch > could be formatted as a separate patch and submitted independently > at a later date. > > 3. Re-formatted the code to the Linux Coding Standards. > The checkpatch script still finds some lines to complain about; > however most of these lines are either (1) lines that I did not change, > or (2) lines that only changed by adding a level of indent which pushed > them over 80-characters, or (3) new lines whose intent is far clearer when > longer than 80-characters. > > 4. Updated the remaining debug print to be significantly more flexible. > This allows control over the amount of debug print to the console -- > which can vary widely. > > 5. Fixed a couple of minor bugs found by testing on a machine with a > very large IO configuration. > > At a high level, this code operates primarily during iommu initialization > and device-driver initialization > > During intel-iommu hardware initialization: > In intel_iommu_init(void) > * If (This is the crash kernel) > . Set flag: crashdump_accepting_active_iommu (all changes below check this) > . Skip disabling the iommu hardware translations > > In init_dmars() > * Duplicate the intel iommu translation tables from the old kernel > in the new kernel > . The root-entry table, all context-entry tables, > and all page-translation-entry tables > . The duplicate tables contain updated physical addresses to link them together. > . The duplicate tables are mapped into kernel virtual addresses > in the new kernel which allows most of the existing iommu code > to operate without change. > . Do some minimal sanity-checks during the copy > . Place the address of the new root-entry structure into "struct intel_iommu" > > * Skip setting-up new domains for 'si', 'rmrr', 'isa' > . Translations for 'rmrr' and 'isa' ranges have been copied from the old kernel > . This patch has not yet been tested with iommu pass-through enabled > > * Existing (unchanged) code near the end of dmar_init: > . Loads the address of the (now new) root-entry structure from > "struct intel_iommu" into the iommu hardware and does the hardware flushes. > This changes the active translation tables from the ones in the old kernel > to the copies in the new kernel. > . This is legal because the translations in the two sets of tables are > currently identical: > Virtualization Technology for Directed I/O. Architecture Specification, > February 2011, Rev. 1.3 (section 11.2, paragraph 2) > > In iommu_init_domains() > * Mark as in-use all domain-id's from the old kernel > . In case the new kernel contains a device that was not in the old kernel > and a new, unused domain-id is actually needed, the bitmap will give us one. > > When a new domain is created for a device: > * If (this device has a context in the old kernel) > . Get domain-id, address-width, and IOVA ranges from the old kernel context; > . Get address(page-entry-tables) from the copy in the new kernel; > . And apply all of the above values to the new domain structure. > * Else > . Create a new domain as normal > > --- > Signed-off-by: Bill Sumner <bill.sumner at hp.com> > > Bill Sumner (6): > Crashdump-Accepting-Active-IOMMU-Flags-and-Prototypes > Crashdump-Accepting-Active-IOMMU-Utility-functions > Crashdump-Accepting-Active-IOMMU-Domain-Interfaces > Crashdump-Accepting-Active-IOMMU-Copy-Translations > Crashdump-Accepting-Active-IOMMU-Debug-Print-IOMMU > Crashdump-Accepting-Active-IOMMU-Call-From-Mainline > > drivers/iommu/intel-iommu.c | 1292 ++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 1224 insertions(+), 68 deletions(-) >
