We are pleased to announce that the Toolchain Microconference has been accepted into the 2020 Linux Plumbers Conference!

The GNU toolchain has direct impact on the development of the Linux kernel and it is imperative that the developers of both ecosystems have an understanding of each other’s needs. Linux Plumbers is the perfect venue for the two communities to interact, and the GNU Toolchain microconference’s purpose is to facilitate that happening.

Last year’s meetup at Linux Plumbers proved that it is critical that the two communities communicate with each other. As a result of last year’s microconference, the GNU toolchain has completed adding support for BPF, in a more flexible and usable way and system call wrappers in glibc were improved. There have been security features derived from the discussions, such as zeroing of registers when entering a function and implicit initialization of atomics.

This year’s topics to be discussed include:

• How to improve the continual communication between GNU toolchain developers and kernel developers.
• Creating a standardization on how to compile the kernel that is suitable for all Live kernel patching frameworks.
• Now that BPF support is in the GNU toolchain, including a new BPF instruction simulator, we’d like some feedback from kernel developers regarding its usability and whether more features are needed.
• Compact C Type Format (CTF) has been added to the GNU toolchain, and there is work underway to also add BTF support. However some useful features are still missing (like backtraces) and their design needs to be discussed and agreed upon among toolchain and kernel developers.

Come and join us in the discussion about innovating the most efficient and functional toolchain for building the Linux kernel.

We hope to see you there!

We are pleased to announce that the Power Management and Thermal Control Microconference has been accepted into the 2020 Linux Plumbers Conference!

Power management and thermal control is an important area in the Linux ecosystem to help with the global environment. Optimizing the amount of work that is achieved while having long battery life and keeping the box from overheating is critical in today’s world. This meeting will focus on continuing to have Linux be an efficient operating system while still lowering the cost of running a data center.

Last year’s meetup at Linux Plumbers resulted in the introduction of thermal pressure support into the CPU scheduler as well as several improvements to the thermal framework, such as a netlink implementation of thermal notification and improvements to CPU cooling. Discussions from last year also helped to improve systems-wide suspend testing tools.

This year’s topics to be discussed include:

• Power capping based on the Energy Model
• Energy Model evolution possibilities
• Regression and performance testing of system-wide suspend
• Warming support in the thermal framework
• Use of running average of temperature for thermal thresholds
• Hardware Feedback Interface support and CPU offline
• CPU power management improvements
• Device power management (runtime PM and system-wide PM) improvements
• Consumer-producer workloads, power distribution

Come and join us in the discussion about extending the battery life of your laptop and keeping it cool.

We hope to see you there!

We are pleased to announce that the RISC-V Microconference has been accepted into the 2020 Linux Plumbers Conference!

The RISC-V ecosystem is gaining momentum at such an astounding speed that it wouldn’t be unfair to compare it to the early days of the Linux ecosystem’s growth. There are a plethora of Linux kernel features that have been added to RISC-V and many more are waiting to be reviewed in the mailing list. Some of them resulted from direct discussions during last year’s RISC-V microconference. For example, RISC-V has a standard boot process along with a well-defined supervisor binary specification (SBI) and cpu hotplug feature. KVM support is very close to being merged and just waiting for official ratification of the H extension. NoMMU support for Linux kernel has already been merged.

Here are a few of the expected topics and current problems in RISC-V Linux land that we would like to cover.

• RISC-V Platform Specification Progress: Unix platform specification added the improved SBI v0.2 specification this year. We will discuss the next set of specifications that should be added to standardize the requirements for RISC-V Linux.
• Making RISC-V Embedded Base Boot Requirement (EBBR) compatible: There are ongoing efforts to add UEFI support for RISC-V Linux kernel. As a result, RISC-V can be fully EBBR compatible. We will discuss the current progress and what’s the best approach to make that happen.
• RISC-V 32-bit glibc port: This will include details about the 64-bit time_t problem and how RISC-V 32 is going to be the first 32-bit architecture with a 64-bit time_t. What still needs to be done for 32-bit support? How do we get this merged? We will also like to discuss the plan to test and maintain it once it is merged.
• Developing and improving BPF JITs using formal verification.: This discussion will review our ongoing efforts of applying the Serval automated formal verification framework to BPF JITs in the Linux kernel. Serval has been used to find new bugs, verify new optimizations, and to develop a new BPF JIT for 32-bit RISC-V. We will discuss possible future roles of formal verification in the JIT development process, and how formal verification can enable future optimizations that would otherwise be difficult to test.
• RISC-V hypervisor extension : The hypervisor extension v0.5 is already available in the latest Qemu and v0.6.1 patches are already in the mailing list. The kvm patchset has been on the mailing list and waiting to be merged. We will discuss the ongoing designs for nested hypervisor implementation.
• An introduction of vector ISA support in RISCV Linux: We will discuss the implementation of vector support in Linux kernel, how user space can get its layout or size and the future work for Linux kernel and glibc.
• RISC-V Linux Tracing Status: The single-step trap exception is an ancient technology that has been supported by many CPU architectures, but RISC-V ISA does not support this feature. By examining the pain points in RISC-V linux kprobe/uprobe development, we want to explore introducing a new single-step hardware mechanism to help the Linux tracing infrastructure.

Come join us and participate in the discussion on how we can improve the support for RISC-V in the Linux kernel.

We hope to see you there!

We are pleased to announce that the LLVM Microconference has been accepted into the 2020 Linux Plumbers Conference!

The LLVM toolchain has made significant progress over the years and many kernel developers are now using it to build their kernels. It is still the one toolchain that can natively compile C into BPF byte code. Clang (the C frontend to LLVM) is used to build Android and ChromeOS kernels and others are in the process of testing to use Clang to build their kernels.

Many topics still need to be resolved, and are planned to be discussed here.
These include (but not limited to):

• Barriers to in-tree Rust support?
• Memory ordering and compiler verification
• Kernel LTO with clang and optimizing using profiling information (PGO and AutoFDO)
• Clang related Continuous Integration topics:
• Improving KernelCI clang integration
• Improving 0day bot clang integration
• Using clang with tuxbuild
• Setting up CI on the LLVM side for Linux kernel builds
• Cross LLVM/binutils testing
• Measuring and improving kernel compile times with Clang
• Builds of LLVM for kernel.org
• Using clang-tidy and clang-format with kernel code
• Coordination between clang and GCC developers on GNU C extensions used in the kernel code
• asm goto w/ outputs (CONFIG_CC_HAS_ASM_GOTO_OUTPUT)
• Parsing issues with genksyms
• clang feedback session; what’s working, what can be improved.

Come and join us in the discussion of improving this new toolchain to make it the most useable
for everyone!

We hope to see you there!