From: Marc Zyngier <maz@xxxxxxxxxx> commit 66e94d5cafd4decd4f92d16a022ea587d7f4094f upstream. It looks like we have tolerated creating mixed-width VMs since... forever. However, that was never the intention, and we'd rather not have to support that pointless complexity. Forbid such a setup by making sure all the vcpus have the same register width. Reported-by: Steven Price <steven.price@xxxxxxx> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Acked-by: Mark Rutland <mark.rutland@xxxxxxx> Link: https://lore.kernel.org/r/20210524170752.1549797-1-maz@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/arm64/include/asm/kvm_emulate.h | 5 +++++ arch/arm64/kvm/reset.c | 28 ++++++++++++++++++++++++---- 2 files changed, 29 insertions(+), 4 deletions(-) --- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h @@ -505,4 +505,9 @@ static __always_inline void __kvm_skip_i write_sysreg_el2(*vcpu_pc(vcpu), SYS_ELR); } +static inline bool vcpu_has_feature(struct kvm_vcpu *vcpu, int feature) +{ + return test_bit(feature, vcpu->arch.features); +} + #endif /* __ARM64_KVM_EMULATE_H__ */ --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -223,6 +223,25 @@ static int kvm_vcpu_enable_ptrauth(struc return 0; } +static bool vcpu_allowed_register_width(struct kvm_vcpu *vcpu) +{ + struct kvm_vcpu *tmp; + bool is32bit; + int i; + + is32bit = vcpu_has_feature(vcpu, KVM_ARM_VCPU_EL1_32BIT); + if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1) && is32bit) + return false; + + /* Check that the vcpus are either all 32bit or all 64bit */ + kvm_for_each_vcpu(i, tmp, vcpu->kvm) { + if (vcpu_has_feature(tmp, KVM_ARM_VCPU_EL1_32BIT) != is32bit) + return false; + } + + return true; +} + /** * kvm_reset_vcpu - sets core registers and sys_regs to reset value * @vcpu: The VCPU pointer @@ -274,13 +293,14 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu } } + if (!vcpu_allowed_register_width(vcpu)) { + ret = -EINVAL; + goto out; + } + switch (vcpu->arch.target) { default: if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) { - if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1)) { - ret = -EINVAL; - goto out; - } pstate = VCPU_RESET_PSTATE_SVC; } else { pstate = VCPU_RESET_PSTATE_EL1;
