Re: xTVAL Compliance restriction proposal
Greg Favor
On Tue, Jun 30, 2020 at 4:19 PM Allen Baum <allen.baum@...> wrote:
One could view the effect of MPRV as changing the mode that is in effect for a memory access. For *tval purposes that end result is all that matters. Ditto for the new-ish HLV/HLVX/HSV instructions. I don't think the new/added hypervisor VS/VU modes change much - since they are supposed to behave like S/U modes. For two-stage translations what matters is the stage that is causing an exception and what that stage's translation mode is. So I believe my admittedly terse statement is correct (albeit without all the extra verbiage describing these various cases). It is the relevant and final/effective privilege/translation modes that matter.
I agree that if VA>PA, then always sign-extending from the implemented address msb works. My statement was addressing the case of PA>VA - in which sign-extending is not always correct. Greg
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