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The [ms]envcfg CSR was added in version 1.12 of the RISC-V privileged ISA (aka S[ms]1p12). However, bits in this CSR are defined by several other extensions which may be implemented separately from any particular version of the privileged ISA (for example, some unrelated errata may prevent an implementation from claiming conformance with Ss1p12). As a result, Linux cannot simply use the privileged ISA version to determine if the CSR is present. It must also check if any of these other extensions are implemented. It also cannot probe the existence of the CSR at runtime, because Linux does not require Sstrict, so (in the absence of additional information) it cannot know if a CSR at that address is [ms]envcfg or part of some non-conforming vendor extension. Since there are several standard extensions that imply the existence of the [ms]envcfg CSR, it becomes unwieldy to check for all of them wherever the CSR is accessed. Instead, define a custom Xlinuxenvcfg ISA extension bit that is implied by the other extensions and denotes that the CSR exists as defined in the privileged ISA, containing at least one of the fields common between menvcfg and senvcfg. This extension does not need to be parsed from the devicetree or ISA string because it can only be implemented as a subset of some other standard extension. Cc: <stable@vger.kernel.org> # v6.7+ Signed-off-by: Samuel Holland <samuel.holland@sifive.com> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Link: https://lore.kernel.org/r/20240228065559.3434837-3-samuel.holland@sifive.com Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.