Hi Julien, On Sun, 2024-02-18 at 18:30 +0000, Julien Grall wrote: > Hi Oleksii, > > Title: Typo s/introdure/introduce/ > > On 05/02/2024 15:32, Oleksii Kurochko wrote: > > The <asm/nospec.h> header is similar between Arm, PPC, and RISC-V, > > so it has been moved to asm-generic. > > I am not 100% convinced that moving this header to asm-generic is a > good > idea. At least for Arm, those helpers ought to be non-empty, what > about > RISC-V? For Arm, they are not taking any action, are they? There are no specific fences or other mechanisms inside evaluate_nospec()/block_speculation() to address speculation.
For RISC-V, it can be implemented in a similar manner, at least for now. Since these functions are only used in the grant tables code ( for Arm and so for RISC-V ), which is not supported by RISC-V. > > If the answer is they should be non-empty. Then I would consider to > keep > the duplication to make clear that each architecture should take > their > own decision in term of security. > > The alternative, is to have a generic implementation that is safe by > default (if that's even possible). I am not certain that we can have a generic implementation, as each architecture may have specific speculation issues. ~ Oleksii
