[PATCH v2 21/25] KVM: arm64: Make TLBI OS/Range UNDEF if not advertised to the guest

[Joey Gouly]

On Tue, Jan 30, 2024 at 08:45:28PM +0000, Marc Zyngier wrote:
> Outer Shareable and Range TLBI instructions shouldn't be made available
> to the guest if they are not advertised. Use FGU to disable those,
> and set HCR_EL2.TLBIOS in the case the host doesn't have FGT. Note
> that in that later case, we cannot efficiently disable TLBI Range
> instructions, as this would require to trap all TLBIs.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kvm/sys_regs.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 39e7c7f74717..f07ee7c89822 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -3948,6 +3948,14 @@ void kvm_init_sysreg(struct kvm_vcpu *vcpu)
>  
>  	mutex_lock(&kvm->arch.config_lock);
>  
> +	/*
> +	 * In the absence of FGT, we cannot independently trap TLBI
> +	 * Range instructions. This isn't great, but trapping all
> +	 * TLBIs would be far worse. Live with it...
> +	 */
> +	if (!kvm_has_feat(kvm, ID_AA64ISAR0_EL1, TLB, OS))
> +		vcpu->arch.hcr_el2 |= HCR_TTLBOS;
> +
>  	if (test_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags))
>  		goto out;
>  
> @@ -3960,6 +3968,32 @@ void kvm_init_sysreg(struct kvm_vcpu *vcpu)
>  				       HFGxTR_EL2_nSMPRI_EL1_MASK	|
>  				       HFGxTR_EL2_nTPIDR2_EL0_MASK);
>  
> +	if (!kvm_has_feat(kvm, ID_AA64ISAR0_EL1, TLB, OS))
> +		kvm->arch.fgu[HFGITR_GROUP] |= (HFGITR_EL2_TLBIRVAALE1OS|
> +						HFGITR_EL2_TLBIRVALE1OS	|
> +						HFGITR_EL2_TLBIRVAAE1OS	|
> +						HFGITR_EL2_TLBIRVAE1OS	|
> +						HFGITR_EL2_TLBIVAALE1OS	|
> +						HFGITR_EL2_TLBIVALE1OS	|
> +						HFGITR_EL2_TLBIVAAE1OS	|
> +						HFGITR_EL2_TLBIASIDE1OS	|
> +						HFGITR_EL2_TLBIVAE1OS	|
> +						HFGITR_EL2_TLBIVMALLE1OS);
> +
> +	if (!kvm_has_feat(kvm, ID_AA64ISAR0_EL1, TLB, RANGE))
> +		kvm->arch.fgu[HFGITR_GROUP] |= (HFGITR_EL2_TLBIRVAALE1	|
> +						HFGITR_EL2_TLBIRVALE1	|
> +						HFGITR_EL2_TLBIRVAAE1	|
> +						HFGITR_EL2_TLBIRVAE1	|
> +						HFGITR_EL2_TLBIRVAALE1IS|
> +						HFGITR_EL2_TLBIRVALE1IS	|
> +						HFGITR_EL2_TLBIRVAAE1IS	|
> +						HFGITR_EL2_TLBIRVAE1IS	|
> +						HFGITR_EL2_TLBIRVAALE1OS|
> +						HFGITR_EL2_TLBIRVALE1OS	|
> +						HFGITR_EL2_TLBIRVAAE1OS	|
> +						HFGITR_EL2_TLBIRVAE1OS);
> +
>  	set_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags);
>  out:
>  	mutex_unlock(&kvm->arch.config_lock);

Commit message update *and* a comment, generous!

Reviewed-by: Joey Gouly <joey.gouly at arm.com>

Thanks,
Joey