Messages in this thread | | | Date | Thu, 5 Jan 2023 22:22:02 +0000 | From | Oliver Upton <> | Subject | Re: [PATCH v5 6/7] KVM: arm64: Mask FEAT_CCIDX |
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On Fri, Dec 30, 2022 at 06:54:51PM +0900, Akihiko Odaki wrote: > The CCSIDR access handler masks the associativity bits according to the > bit layout for processors without FEAT_CCIDX. KVM also assumes CCSIDR is > 32-bit where it will be 64-bit if FEAT_CCIDX is enabled. Mask FEAT_CCIDX > so that these assumptions hold. > > Suggested-by: Marc Zyngier <maz@kernel.org> > Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
FYI, I'm an idiot and replied to v4 of this patch... Forwarding comments below:
> --- > arch/arm64/kvm/sys_regs.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index f4a7c5abcbca..aeabf1f3370b 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1124,6 +1124,12 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc const *r > ID_DFR0_PERFMON_SHIFT, > kvm_vcpu_has_pmu(vcpu) ? ID_DFR0_PERFMON_8_4 : 0); > break; > + case SYS_ID_AA64MMFR2_EL1: > + val &= ~ID_AA64MMFR2_EL1_CCIDX_MASK; > + break; > + case SYS_ID_MMFR4_EL1: > + val &= ~ARM64_FEATURE_MASK(ID_MMFR4_CCIDX); > + break;
Not that it is necessarily worth addressing, but I wanted to point something out.
This change breaks migration from older kernels on implementations w/ FEAT_CCIDX. There is most likely exactly 0 of those in the wild, but we need to be careful changing user-visible stuff like this.
-- Thanks, Oliver
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