Re: [PATCH v4 7/9] riscv: vector: adjust minimum Vector requirement to ZVE32X

On Thu, Apr 18, 2024 at 11:41:29AM -0700, Eric Biggers wrote:

If the RISC-V kernel ever disables V, then it should also disable everything that depends on V.

This would be similar to how on x86, if the kernel decides to disable AVX to mitigate the Gather Data Sampling vulnerability, it also disables AVX2, AVX512, VAES, VPCLMULQDQ, etc. See cpuid_deps[] in arch/x86/kernel/cpu/cpuid-deps.c.

Sometimes CPU features depend on other ones. That's just the way things work.

🤨

Whenever possible that should be handled centrally, not pushed down to every user both in-kernel and userspace.

FWIW, anything detected but rejected while probing the DT or ACPI tables will cause riscv_isa_extension_available() (or other APIs) to return false.