Hey Marc, On Fri, Oct 29, 2021 at 4:31 AM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > On Fri, 29 Oct 2021 01:32:02 +0100, > Oliver Upton <oupton@xxxxxxxxxx> wrote: [...] > > case SYS_ID_AA64DFR0_EL1: > > - /* Limit debug to ARMv8.0 */ > > + /* Limit debug to ARMv8.2 */ > > val &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_DEBUGVER); > > - val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_DEBUGVER), 6); > > + val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_DEBUGVER), 8); > > + > > + /* Hide DoubleLock from guests */ > > + val &= ~ARM64_FEATURE_MASK(ID_AA64DFR0_DOUBLELOCK); > > + val |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64DFR0_DOUBLELOCK), 0CF); > > + > > One issue with that is that this will break migration from an older > kernel (DFR0 will be different between source and destination). > > You'll need a set_user handler and deal with it in a similar way to > CSV2/CSV3. Yeah, definitely so. In that case, unless we're strongly motivated to expose these changes soon, I'll just punt the ID register changes until Reiji's series [1] lands, as anything I add for a writable DFR0 will invariably be scrapped in favor of his work. I'll post v2 of this series folding in your feedback (thx for quick review, btw), less this patch. [1] https://patchwork.kernel.org/project/kvm/cover/20211012043535.500493-1-reijiw@xxxxxxxxxx/ -- Thanks, Oliver
