On Fri, 19 Mar 2021 12:01:28 +0000, Andre Przywara wrote:
> The "First Fault Register" (FFR) is an SVE register that mimics a
> predicate register, but clears bits when a load or store fails to handle
> an element of a vector. The supposed usage scenario is to initialise
> this register (using SETFFR), then *read* it later on to learn about
> elements that failed to load or store. Explicit writes to this register
> using the WRFFR instruction are only supposed to *restore* values
> previously read from the register (for context-switching only).
> As the manual describes, this register holds only certain values, it:
> "... contains a monotonic predicate value, in which starting from bit 0
> there are zero or more 1 bits, followed only by 0 bits in any remaining
> bit positions."
> Any other value is UNPREDICTABLE and is not supposed to be "restored"
> into the register.
>
> [...]
Applied to arm64 (for-next/fixes), thanks!
[1/1] kselftest/arm64: sve: Do not use non-canonical FFR register value
https://git.kernel.org/arm64/c/7011d72588d1
Cheers,
--
Will
https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev
