On Mon, Nov 05, 2018 at 09:52:52AM +0100, Arnd Bergmann wrote: > > I fundamentally disagree with this… and think it should be the contrary. > > > > 1. The kernel shall support no vendor specific instructions whatsoever, > > period. > > I think what was meant above is > > 1. If a vendor extension requires kernel support, that support > must be able to be built into a kernel image without breaking support > for CPUs that do not have that extension, to allow building a single > kernel image that works on all CPUs.
No. This literally means no vendor extensions involving instructions or CSRs in the kernel. They are fine for userspace, or for the M-mode code including impementation of the SBI, but not for the kernel.
