On 2021/2/4 5:38, Will Deacon wrote: > On Wed, Feb 03, 2021 at 11:15:18AM +0800, Zhou Wang wrote: >> On 2021/1/29 17:06, Zhou Wang wrote: >>> This RFC series is the followed patch of this discussion: >>> https://www.spinics.net/lists/arm-kernel/msg866187.html. >>> >>> Currently there is no debug interface about SMMUv3 driver, which makes it >>> not convenient when we want to dump some information, like the value of >>> CD/STE, S1/S2 page table, SMMU registers or cmd/event/pri queues. >>> >>> This series tries to add support of dumping CD/STE and page table. The >>> interface design is that user sets device/pasid firstly by sysfs files >>> and then read related sysfs file to get information: >>> >>> (currently only support PCI device) >>> echo <domain>:<bus>:<dev>.<fun> > /sys/kernel/debug/iommu/smmuv3/pci_dev >>> echo <pasid> > /sys/kernel/debug/iommu/smmuv3/pasid >>> >>> Then value in CD and STE can be got by: >>> cat /sys/kernel/debug/iommu/smmuv3/ste >>> cat /sys/kernel/debug/iommu/smmuv3/cd >>> >>> S1 and S2 page tables can be got by: >>> cat /sys/kernel/debug/iommu/smmuv3/pt_dump_s1 >>> cat /sys/kernel/debug/iommu/smmuv3/pt_dump_s2 >>> >>> For STE, CD and page table, related device and pasid are set in pci_dev >>> and pasid files as above. >>> >>> First and second patch export some help functions or macros in arm-smmu-v3 >>> and io-pgtable-arm codes, so we can reuse them in debugfs.c. As a RFC, this >>> series does not go further to dump SMMU registers and cmd/event/pri queues. >>> I am not sure this series is in the right way, so let's post it out and >>> have a >>> discussion. Looking forward to any feedback. >>> >>> Zhou Wang (3): >>> iommu/arm-smmu-v3: Export cd/ste get functions >>> iommu/io-pgtable: Export page table walk needed functions and macros >>> iommu/arm-smmu-v3: Add debug interfaces for SMMUv3 >>> >>> drivers/iommu/Kconfig | 11 + >>> drivers/iommu/arm/arm-smmu-v3/Makefile | 1 + >>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 10 +- >>> drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 10 + >>> drivers/iommu/arm/arm-smmu-v3/debugfs.c | 398 >>> ++++++++++++++++++++++++++++ >>> drivers/iommu/io-pgtable-arm.c | 47 +--- >>> drivers/iommu/io-pgtable-arm.h | 43 +++ >>> 7 files changed, 475 insertions(+), 45 deletions(-) >>> create mode 100644 drivers/iommu/arm/arm-smmu-v3/debugfs.c >>> >> >> Any comments about this series? > > Truthfully, I don't really see the use in dumping the state of the SMMU > data structures. They're not especially dynamic, and there are higher level > ways to determine how devices map to groups etc.
Here the aim is not to find the device/groups maps, but to dump CD/STE value. Of cause, we can know them from reading codes, however, we expect to dump hardware configures quickly and directly when debugging hardware related problem. It is a real pain when your hardware guy ask you to do this :) > > However, I can see some utility in dumping the page-tables. We have that > functionality for the CPU side via /sys/kernel/debug/kernel_page_tables, > so something similar in the io-pgtable code could be quite neat. In > particular, the logic to expose things in debugfs and drive the dumping > could be agnostic of the page-table format, while the formats themselves Do you mean different page-table format, like 64_s1, 64_s2, 32_s1, 32_s2? Seems in io-pgtable code, we only tell them in arm_lpae_prot_to_pte, and currently in this RFC patch, we do not print attributes. Thanks, Zhou > coule implement optional callback(s) to return the data. > > Will > > . > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
