On Fri, Jun 04, 2021 at 03:01:17PM +0100, Mark Rutland wrote: > On Thu, Jun 03, 2021 at 07:33:44PM +0100, Will Deacon wrote: > > Ignore 'kvm-arm.mode=protected' when using VHE so that kvm_get_mode() > > only returns KVM_MODE_PROTECTED on systems where the feature is available. > > IIUC, since the introduction of the idreg-override code, and the > mutate_to_vhe stuff, passing 'kvm-arm.mode=protected' should make the > kernel stick to EL1, right? So this should only affect M1 (or other HW > with a similar impediment).
It's not just about the M1, unfortunately. You can boot with: "kvm-arm.mode=protected id_aa64mmfr1.vh=1" which will force VHE mode, so we should fail protected mode in that case. > One minor comment below; otherwise: > > Acked-by: Mark Rutland <mark.rutl...@arm.com> Thanks, I'll keep the tag but please yell if you want me to drop it. > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > > index efed2830d141..dc1f2e747828 100644 > > --- a/arch/arm64/kernel/cpufeature.c > > +++ b/arch/arm64/kernel/cpufeature.c > > @@ -1773,15 +1773,7 @@ static void cpu_enable_mte(struct > > arm64_cpu_capabilities const *cap) > > #ifdef CONFIG_KVM > > static bool is_kvm_protected_mode(const struct arm64_cpu_capabilities > > *entry, int __unused) > > { > > - if (kvm_get_mode() != KVM_MODE_PROTECTED) > > - return false; > > - > > - if (is_kernel_in_hyp_mode()) { > > - pr_warn("Protected KVM not available with VHE\n"); > > - return false; > > - } > > - > > - return true; > > + return kvm_get_mode() == KVM_MODE_PROTECTED; > > } > > #endif /* CONFIG_KVM */ > > > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > > index 1cb39c0803a4..8d5e23198dfd 100644 > > --- a/arch/arm64/kvm/arm.c > > +++ b/arch/arm64/kvm/arm.c > > @@ -2121,7 +2121,11 @@ static int __init early_kvm_mode_cfg(char *arg) > > return -EINVAL; > > > > if (strcmp(arg, "protected") == 0) { > > - kvm_mode = KVM_MODE_PROTECTED; > > + if (!is_kernel_in_hyp_mode()) > > + kvm_mode = KVM_MODE_PROTECTED; > > + else > > + pr_warn_once("Protected KVM not available with VHE\n"); > > ... assuming this is only for M1, it might be better to say: > > Protected KVM not available on this hardware > > ... since that doesn't suggest that other VHE-capable HW is also not > PKVM-capable. I'm just moving the existing string here, but as above, it's not M1 specific. Will _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm