[PATCH 2/5] KVM: arm64: Force trap of GMID_EL1 when the guest doesn't have MTE

[Joey Gouly]

On Thu, Nov 20, 2025 at 01:31:59PM +0000, Marc Zyngier wrote:
> If our host has MTE, but the guest doesn't, make sure we set HCR_EL2.TID5
> to force GMID_EL1 being trapped.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/kvm/sys_regs.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 84e6f04220589..40f32b017f107 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -5558,6 +5558,8 @@ static void vcpu_set_hcr(struct kvm_vcpu *vcpu)
>  
>  	if (kvm_has_mte(vcpu->kvm))
>  		vcpu->arch.hcr_el2 |= HCR_ATA;
> +	else if (id_aa64pfr1_mte(read_sanitised_ftr_reg(SYS_ID_AA64PFR1_EL1)))
> +		vcpu->arch.hcr_el2 |= HCR_TID5;

This is because we want to enable the trapping regardless of CONFIG_ARM64_MTE
(so we can't use system_supports_mte()).

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

>  
>  	/*
>  	 * In the absence of FGT, we cannot independently trap TLBI
> -- 
> 2.47.3
>