Hi Andrea, On Mon, Mar 16, 2020 at 02:09:07PM +0000, Mark Rutland wrote: > AFAICT, this series relies on: > > * An ISB completing prior page table walks when updating TTBR. I don't > believe this is necessarily the case, given how things work for an > EL1->EL2 transition where there can be ongoing EL1 walks. I've had confirmation that a DSB is necessary (after the MSR and ISB) to complete any ongoing translation table walks for the stale context. Without a DSB, those walks can observe subsequent stores and encounter the usual set of CONSTRAINED UNPREDICTABLE behaviours (e.g. walking into MMIO with side-effects, continuing from amalgamted entries, etc). Those issues are purely to do with the walk, and apply regardless of whether the resulting translations are architecturally consumed. > * Walks never being initiated for `inactive` contexts within the current > translation regime. e.g. while ASID x is installed, never starting a > walk for ASID y. I can imagine that the architecture may permit a form > of this starting with intermediate walk entries in the TLBs. I'm still chasing this point. Thanks, Mark.
