On 06/11/18 08:06, Christoffer Dall wrote: > On Mon, Nov 05, 2018 at 02:36:15PM +0000, Marc Zyngier wrote: >> It is a bit odd that we only install stage-2 translation after having >> cleared HCR_EL2.TGE, which means that there is a window during which >> AT requests could fail as stage-2 is not configured yet. >> >> Let's move stage-2 configuration before we clear TGE, making the >> guest entry sequence clearer: we first configure all the guest stuff, >> then only switch to the guest translation regime. >> >> Non-VHE doesn't have that kind of behaviour, and is left alone. > > I'm a bit confused about this statement. You can still issue a S12E1x > AT instruction after activating traps (setting HCR_EL2.VM) on non-VHE > and get at the same behavior, right? > > Is the point here that we are not aware of any non-VHE implementations > that speculate AT instructions in this window, or am I missing some > architectural nugget that prevents problems on non-VHE systems? You're right. This is not an issue on non-VHE so far because we don't know of any such system that is broken in such a way (speculative AT instruction leading to inconsistent TLBs). > In any case, why not change the non-VHE code as well to preserve > symmetry for both types of systems? Happy to change that too. Thanks, M. -- Jazz is not dead. It just smells funny...
