On Fri, May 15, 2020 at 01:04:33PM +0100, Szabolcs Nagy wrote: > The 05/15/2020 12:27, Catalin Marinas wrote: > > Thanks Szabolcs. While we are at this, no-one so far asked for the > > GCR_EL1.RRND to be exposed to user (and this implies RGSR_EL1.SEED). > > Since RRND=1 guarantees a distribution "no worse" than that of RRND=0, I > > thought there isn't much point in exposing this configuration to the > > user. The only advantage of RRND=0 I see is that the kernel can change > > it seems RRND=1 is the impl specific algorithm. Yes, that's the implementation specific algorithm which shouldn't be worse than the standard one. > > the seed randomly but, with only 4 bits per tag, it really doesn't > > matter much. > > > > Anyway, mentioning it here in case anyone is surprised later about the > > lack of RRND configurability. > > i'm not familiar with how irg works. It generates a random tag based on some algorithm. > is the seed per process state that's set up at process startup in some > way? or shared (and thus effectively irg is non-deterministic in > userspace)? The seed is only relevant if the standard algorithm is used (RRND=0). -- Catalin
