On Fri, 29 Oct 2021 01:32:02 +0100, Oliver Upton <oupton@xxxxxxxxxx> wrote: > > The additions made to the Debug architecture between v8.0 and v8.2 are > only applicable to external debug. KVM does not (and likely will never) > support external debug, so KVM can proudly report support for v8.2 to > its guests. > > Raise the reported Debug architecture to v8.2. Additionally, v8.2 makes > FEAT_DoubleLock optional. Even though KVM never supported it in the > first place, report DoubleLock as not implemented now as the > architecture permits it for v8.2. > > Cc: Reiji Watanabe <reijiw@xxxxxxxxxx> > Cc: Ricardo Koller <ricarkol@xxxxxxxxxx> > Suggested-by: Marc Zyngier <maz@xxxxxxxxxx> > Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx> > --- > arch/arm64/kvm/sys_regs.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 0840ae081290..f56ee5830d18 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1109,9 +1109,14 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, > ARM64_FEATURE_MASK(ID_AA64ISAR1_GPI)); > break; > 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. Thanks, M. -- Without deviation from the norm, progress is not possible.
