Many RISC-V Improvements Ready For Linux 5.5: M-Mode, SECCOMP, Other Features
Written by Michael Larabel in Hardware on 27 November 2019 at 04:22 AM EST. 3 Comments
HARDWARE --
The RISC-V kernel code has some interesting changes ready for Linux 5.5.

Among the RISC-V changes for the in-development Linux 5.5 kernel include:

- M-Mode support, which is the highest privilege mode for RISC-V and typically reserved for the system firmware. The M-Mode has access to all resource and interrupts while normally RISC-V kernels run in the lower S-Mode privilege level. The motivation for the M-Mode kernel support appears to be CPU-level interrupt controller functionality.

- SECCOMP secure computing mode support now works on RISC-V.

- "nommu" support to run without MMU-based memory management support enabled/working.

- Support for running with SBI (Supervisor Binary Interface) mode disabled due to those calls being expensive.

- TLB flush optimizations by doing local TLB flushes when possible rather than SBI-based flushes that are more expensive.

- The kernel now passes the complete RISC-V ISA string to user-space rather than redacting parts of it.

- The kernel Makefile for RISC-V now supports BZ2 / LZ4 / LZMA / LZO kernel image compression formats similar to what is supported for other CPU architectures.

The complete list of RISC-V architecture changes via this pull request.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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