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Ampere Altra™ Linux Kernel Porting Guide
Introduction
This guide provides information regarding Linux kernel features and patches that apply to the Ampere Altra™ SoC. It provides a guideline regarding accepted, posted, and pending but not yet posted kernel patches that may assist developers in porting their kernels to support SoC features.
This document assumes a stock Linux kernel version 4.18 base, which can be found here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/ .
For any question, please contact the Ampere support team: support@amperecomputing.com
Note: the eMag kernel wiki has been moved here: https://github.com/AmpereComputing/ampere-centos-kernel/wiki/Ampere-CentOS-7.5-Kernel-wiki
Linux Kernel Features
The Linux 4.18 kernel contains many SoC features already; there is no high-level feature missing. Note that there is, however, platform functionality (i.e USB, etc.) that requires backporting to 4.18 listed below.
SoC Kernel Repositories
The table below shows the repositories for the Ampere Altra kernel, which are based on the stock CentOS Linux kernel.
| Repositories | Comment |
| https://github.com/AmpereComputing/ampere-altra-kernel |
Ampere Altra kernel GIT repository- Branch amp-altra-8.0-kernel: kernel 4.18 for Ampere Altra |
| https://github.com/AmpereComputing/ampere-altra-build | Ampere Altra kernel RPM compiling GIT repository- Branch ampere-altra-8.0-build: kernel 4.18 RPM’s for Ampere Altra |
Kernel Configuration
There is no Ampere Altra kernel specific configuration file, it relies on the default configuration. In general, the default will include all that is needed. You can confirm that all required drivers are included by cross checking with the table below.
| Kernel Configuration | Comment |
| CONFIG_SENSORS_XGENE | SoC temperature/power sensors driver |
| CONFIG_I2C_XGENE_SLIMPRO | I2C interface driver to boot processor |
| CONFIG_I2C_DESIGNWARE_PLATFORM | I2C driver for bus directly expose to the OS |
| CONFIG_I2C_DESIGNWARE_CORE | I2C driver for bus directly expose to the OS |
| CONFIG_SERIAL_AMBA_PL011 | Serial console driver |
| CONFIG_SERIAL_AMBA_PL011_CONSOLE | Serial console driver |
| CONFIG_ACPI_BUTTON | Require for power off support |
| CONFIG_ACPI_XXXX | General ACPI support configuration |
| CONFIG_ARM64 | General ARM64 support |
| CONFIG_PCI | General PCIe support |
Ampere Altra Patches
This section describes all patches related to Altra. In general, all patches are targeted for upstream. The only exception is patch marked with “NOUPSTREAM" [MM1]. These patches - with no intention to upstream - may have one or more of the following reasons:
● Back ported patch and not applicable for upstream
● Patch will never be accepted upstream as there is another solution in-flight
● Patch applicable to a specific individual and have no overall benefit to all or to the maintainer
● Patch will never be accepted upstream but may be beneficial to a specific version of the kernel
Patches are separate into three categories – required, optional, and obsolete. Required patches are minimum patch required to have a bootable, working, and with reasonable system performance. Optional patches are patches that provide extra features but not required to have a basic working system. Obsolete patches are patches that are no longer relevant.
Linux Kernel 4.18 Required Patches
USB
These patches are required to properly support USB on Altra platforms. Without this patch set, pre-5.3 kernels will crash on boot:
| Accepted Kernel | Hash Tag | Subject |
| 5.3 | 2daaefd [MM2] | BACKPORT: lib/genalloc: add gen_pool_dma_zalloc() for zeroed DMA allocations |
| 5.3 | 56ae2a91 | BACKPORT: USB: use genalloc for USB HCs with local memory |
| 5.3 | 920eeec8 | BACKPORT: USB: drop HCD_LOCAL_MEM flag |
| 5.3 | 391bde5 | BACKPORT: usb: don't create dma pools for HCDs with a localmem_pool |
| 5.3 | cea1f46 | BACKPORT: usb: add a hcd_uses_dma helper |
PMU
These driver patches are required to support DMC-/b65054597872ce3aefbc6a666385eabdf9e288da, CMN-600, ARM DSU, SPE PMU:
| Accepted Kernel | Hash Tag | Subject |
| CMN-600 | ||
| 5.14 | 5384c1c | perf/arm-cmn: Fix invalid pointer when access dtc object sharing the same IRQ number |
| 5.10 | eea0670 | BACKPORT: perf: Add Arm CMN-600 DT binding |
| 5.10 | 4ccd6fc | BACKPORT: perf: Add Arm CMN-600 PMU driver |
| 5.10 | 8db02c8 | BACKPORT: perf/arm-cmn: Add ACPI support |
| N/A | 55e935b | NOUPSTREAM [MM3] : centos: defconfig: Add CMN-600 PMU support |
| TBD | 19a1b38 | Perf: arm-cmn: Allow irq to be shared. |
| TBD | c6f079f | perf: arm_cmn: improve and make it work on 2P. |
| ARM SPE | ||
| 5.0 | 2f798e1 | BACKPORT: crypto: authenc - fix parsing key with misaligned rta_len |
| 5.3 | 44e81d2 | BACKPORT: ACPI/PPTT: Modify node flag detection to find last IDENTICAL |
| 5.3 | 2c70ac1 | BACKPORT: ACPI/PPTT: Add function to return ACPI 6.3 Identical tokens |
| 5.3 | fb577aa | BACKPORT: arm_pmu: acpi: spe: Add initial MADT/SPE probing |
| 5.3 | 068ff4a | BACKPORT: perf: arm_spe: Enable ACPI/Platform automatic module loading |
| 5.1 | 51df9ae | BACKPORT: ACPICA: ACPI 6.3: PPTT add additional fields in Processor S… |
| 5.1 | 537f45c | BACKPORT: ACPICA: ACPI 6.3: MADT: add support for statistical profili… |
| N/A | 44fb326 | NOUPSTREAM: [MM4] centos: defconfig: Add ARM SPE PMU support |
| ARM DSU | ||
| TBD | c015bb2 | perf: arm_dsu: Allow IRQ to be shared among devices. |
| 5.10 | d5b4ea2 | perf: arm_dsu: Support DSU ACPI devices (perf: arm_dsu: Support ACPI mode.) |
| N/A | 63fbb8b | NOUPSTREAM: centos: defconfig: Enable ARM_DSU_PMU support |
| ARM DMC-620 | ||
| 5.11 | e287be8 | perf: Add ARM DMC-620 PMU driver. |
| N/A | 2f21c8a | NOUPSTREAM: centos: defconfig: Add DMC-620 PMU support |
| N/A | 871759d | NOUPSTREAM: perf: arm_dmc620: Update ACPI ID. (DMC-620 Driver will include this) |
| ARM SMMUv3 PMU (PMCG) | ||
| 5.1 | 0a24ea6 | perf/core: Add function to test for event exclusion flags. |
| 5.1 | 23353f8 | BACKPORT: perf/core: Add PERF_PMU_CAP_NO_EXCLUDE for exclusion incapable PMUs. |
| 5.2 | 90314cd | BACKPORT: ACPI/IORT: Add support for PMCG. |
| 5.2 | 1fa69b2 | BACKPORT: perf/smmuv3: Add arm64 smmuv3 pmu driver. |
| 5.2 | 6f3efbe | BACKPORT: perf/smmuv3: Add MSI irq support. |
| 5.4 | 236a28b | BACKPORT: perf/smmuv3: Validate group size. |
| 5.4 | 9482e6e | BACKPORT: perf/smmuv3: Validate groups for global filtering. |
| 5.5 | 43046fc | BACKPORT: perf/smmuv3: Remove the leftover put_cpu() in error path In… |
| 5.8 | 1164351 | Allow sharing MMIO registers with the SMMU driver. |
| 5.8 | 4964038 | ACPI/IORT: Fix PMCG node always look for a single ID mapping. |
| N/A | 283833f | NOUPSTREAM: perf: arm_cmn: add new code drop off from ARM. |
| N/A | cb4b1ac | NOUPSTREAM: centos: defconfig: Enable ARM_SMMU_V3_PMU config |
| KVM | ||
| 5.2 | 7b8a53c | BACKPORT: arm64: KVM: Enable VHE support for :G/:H perf event modifiers |
| 5.2 | 4a447c5 | BACKPORT: arm64: KVM: Add accessors to track guest/host only counters |
| 5.2 | cd9edc4 | BACKPORT: arm64: KVM: Encapsulate kvm_cpu_context in kvm_host_data |
| 5.2 | 095370f | BACKPORT: arm/arm64: KVM: Statically configure the host's view of MPIDR |
NUMA
These patches provide multi-socket optimization:
| Accepted Kernel | Hash Tag | Subject |
| 5.8 or see below | N/A | [PATCH v2 00/20] mm: rework free_area_init*() funcitons |
| 5.10 | 2a13c13 | arm64: NUMA: Kconfig: Increase NODES_SHIFT to 4 |
| N/A | 9db4e45 | NOUPSTREAM: arm64: Kconfig: Enable NODES_SPAN_OTHER_NODES config for NUMA |
COMPILER
These patches are required for compilation with the Ampere compiler (based on GCC: https://www.gnu.org/software/gcc/ ): https://developer.amperecomputing.com/resources/ :
| Accepted Kernel | Hash Tag | Subject |
| N/A | f9311e4 | NOUPSTREAM: scripts: Fix compilation error when using Ampere native toolchain |
| N/A | 0b31158 | NOUPSTREAM: Workaround Ampere gcc issue with loop-optimization when building perf |
ARM64
This patch is required to fix a kernel crash:
| Accepted Kernel | Hash Tag | Subject |
| 5.0 | 5db43ff | BACKPORT: efi/arm: Revert "Defer persistent reservations until after paging_init()" |
These patches are required to expose side channel vulnerability mitigation visibility to sysfs:
| Accepted Kernel | Hash Tag | Subject |
| 5.2 | b6f5d5c | BACKPORT: arm64: add sysfs vulnerability show for meltdown |
| 5.2 | be1dbd0 | BACKPORT: arm64: Add sysfs vulnerability show for spectre-v1 |
| N/A (5.2) | 9d345e4 | NOUPSTREAM: VARIANT 2: arm64: add vulnerability show for retpoline spectre-v2 [MM5] |
This patch is required to fix PCI ECAM reading:
| Accepted Kernel | Hash Tag | Subject |
| 5.10 | 0d8dd94 | drivers/pci: Add ecam quirk for Ampere Altra SOC. |
This patch is required to fix soft lockup during heavy stress test:
| Accepted Kernel | Hash Tag | Subject |
| 5.8 | d6f5dfc | BACKPORT: Split the old READ_IMPLIES_EXEC workaround from executable. |
Crypto[MM6]
These patches are required to fix kernel crashes during LTP testing:
| Accepted Kernel | Hash Tag | Subject |
| 5.0 | 2f798e1 | BACKPORT: crypto: authenc - fix parsing key with misaligned rta_len |
| 5.2 | a9b2432 | BACKPORT: crypto: user - prevent operating on larval algorithms |
APEI
These patches are required to support APEI/RAS features:
| Accepted Kernel | Hash Tag | Subject |
| 5.1 | d2e5e81 | BACKPORT: ACPI / APEI: Don't wait to serialise with oops messages when panic()ing |
| 5.1 | 460f959 | BACKPORT: ACPI / APEI: Remove silent flag from ghes_read_estatus() |
| 5.1 | a33b383 | BACKPORT: ACPI / APEI: Switch estatus pool to use vmalloc memory |
| 5.1 | 9778f65 | BACKPORT: ACPI / APEI: Make hest.c manage the estatus memory pool |
| 5.1 | 2888525 | BACKPORT: ACPI / APEI: Make estatus pool allocation a static size |
| 5.1 | 9ae38f2 | BACKPORT: ACPI / APEI: Don't store CPER records physical address in struct ghes |
| 5.1 | ab202ee | BACKPORT: ACPI / APEI: Remove spurious GHES_TO_CLEAR check |
| 5.1 | f36998d | BACKPORT: ACPI / APEI: Don't update struct ghes' flags in read/clear estatus |
| 5.1 | fb2bfdc | BACKPORT: ACPI / APEI: Generalise the estatus queue's notify code |
| 5.1 | 6c070ab | BACKPORT: ACPI / APEI: Don't allow ghes_ack_error() to mask earlier errors |
| 5.1 | 2dae32f | BACKPORT: ACPI / APEI: Move NOTIFY_SEA between the estatus-queue and NOTIFY_NMI |
| 5.1 | 7e0c9ae | BACKPORT: ACPI / APEI: Switch NOTIFY_SEA to use the estatus queue |
| 5.1 | f78e808 | BACKPORT: KVM: arm/arm64: Add kvm_ras.h to collect kvm specific RAS plumbing |
| 5.1 | ab77d4b | BACKPORT: arm64: KVM/mm: Move SEA handling behind a single 'claim' interface |
| 5.1 | 2ff3da1 | BACKPORT: ACPI / APEI: Move locking to the notification helper |
| 5.1 | 71b03af | BACKPORT: ACPI / APEI: Let the notification helper specify the fixmap slot |
| 5.1 | 15304bd | BACKPORT: ACPI / APEI: Pass ghes and estatus separately to avoid a later copy |
| 5.1 | 4c66fd1 | BACKPORT: ACPI / APEI: Make GHES estatus header validation more user friendly |
| 5.1 | a90df19 | BACKPORT: ACPI / APEI: Split ghes_read_estatus() to allow a peek at the CPER length |
| 5.1 | de8192e | BACKPORT: ACPI / APEI: Only use queued estatus entry during in_nmi_queue_one_entry() |
| 5.1 | 073712f | BACKPORT: ACPI / APEI: Use separate fixmap pages for arm64 NMI-like notifications |
| 5.8 | f845034 | BACKPORT: mm/memory-failure: Add memory_failure_queue_kick() |
| 5.8 | ac5d13a | BACKPORT: ACPI / APEI: Kick the memory_failure() queue for synchronous err |
| 5.8 | 76f72cb | BACKPORT: arm64: acpi: Make apei_claim_sea() synchronise with APEI's irq work |
| 5.1 | 535e7eb | BACKPORT: firmware: arm_sdei: Add ACPI GHES registration helper |
| 5.1 | e2b0f47 | BACKPORT: ACPI / APEI: Add support for the SDEI GHES Notification type |
HW Monitor
These patches are required to support HW monitor:
| Accepted Kernel | Hash Tag | Subject |
| TBD | f2e6dee | hwmon: Add Ampere Altra HW monitor driver |