On Mon, May 24, 2021 at 06:07:52PM +0100, Marc Zyngier wrote:
> 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.pr...@arm.com>
> Signed-off-by: Marc Zyngier <m...@kernel.org>
> Cc: sta...@vger.kernel.org
Looks good to me!
Acked-by: Mark Rutland <mark.rutl...@arm.com>
Mark.
> ---
>
> Notes:
> v2: Fix missing check against ARM64_HAS_32BIT_EL1 (Mark)
>
> arch/arm64/include/asm/kvm_emulate.h | 5 +++++
> arch/arm64/kvm/reset.c | 28 ++++++++++++++++++++++++----
> 2 files changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_emulate.h
> b/arch/arm64/include/asm/kvm_emulate.h
> index f612c090f2e4..01b9857757f2 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -463,4 +463,9 @@ static __always_inline void kvm_incr_pc(struct kvm_vcpu
> *vcpu)
> vcpu->arch.flags |= KVM_ARM64_INCREMENT_PC;
> }
>
> +static inline bool vcpu_has_feature(struct kvm_vcpu *vcpu, int feature)
> +{
> + return test_bit(feature, vcpu->arch.features);
> +}
> +
> #endif /* __ARM64_KVM_EMULATE_H__ */
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 956cdc240148..d37ebee085cf 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -166,6 +166,25 @@ static int kvm_vcpu_enable_ptrauth(struct kvm_vcpu *vcpu)
> 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
> @@ -217,13 +236,14 @@ 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;
> --
> 2.30.2
>
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