[PATCH 24/25] KVM: arm64: Make FEAT_MOPS UNDEF if not advertised to the guest

[Joey Gouly]

On Mon, Jan 22, 2024 at 08:18:51PM +0000, Marc Zyngier wrote:
> We unconditionally enable FEAT_MOPS, which is obviously wrong.
> 
> So let's only do that when it is advertised to the guest.
> Which means we need to rely on a per-vcpu HCRX_EL2 shadow register.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
>  arch/arm64/include/asm/kvm_arm.h        | 4 +---
>  arch/arm64/include/asm/kvm_host.h       | 1 +
>  arch/arm64/kvm/hyp/include/hyp/switch.h | 2 +-
>  arch/arm64/kvm/sys_regs.c               | 8 ++++++++
>  4 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 3c6f8ba1e479..a1769e415d72 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -102,9 +102,7 @@
>  #define HCR_HOST_NVHE_PROTECTED_FLAGS (HCR_HOST_NVHE_FLAGS | HCR_TSC)
>  #define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H)
>  
> -#define HCRX_GUEST_FLAGS \
> -	(HCRX_EL2_SMPME | HCRX_EL2_TCR2En | \
> -	 (cpus_have_final_cap(ARM64_HAS_MOPS) ? (HCRX_EL2_MSCEn | HCRX_EL2_MCE2) : 0))
> +#define HCRX_GUEST_FLAGS (HCRX_EL2_SMPME | HCRX_EL2_TCR2En)
>  #define HCRX_HOST_FLAGS (HCRX_EL2_MSCEn | HCRX_EL2_TCR2En)
>  
>  /* TCR_EL2 Registers bits */
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index fe5ed4bcded0..22343354db3e 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -584,6 +584,7 @@ struct kvm_vcpu_arch {
>  
>  	/* Values of trap registers for the guest. */
>  	u64 hcr_el2;
> +	u64 hcrx_el2;
>  	u64 mdcr_el2;
>  	u64 cptr_el2;
>  
> diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
> index 2d5891518006..e3fcf8c4d5b4 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/switch.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
> @@ -236,7 +236,7 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
>  	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
>  
>  	if (cpus_have_final_cap(ARM64_HAS_HCX)) {
> -		u64 hcrx = HCRX_GUEST_FLAGS;
> +		u64 hcrx = vcpu->arch.hcrx_el2;
>  		if (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)) {
>  			u64 clr = 0, set = 0;
>  
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index afe6975fcf5c..b7977e08e4ef 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -3952,6 +3952,14 @@ void kvm_init_sysreg(struct kvm_vcpu *vcpu)
>  	if (!kvm_has_feat(kvm, ID_AA64ISAR0_EL1, TLB, OS))
>  		vcpu->arch.hcr_el2 |= HCR_TTLBOS;
>  
> +	if (cpus_have_final_cap(ARM64_HAS_HCX)) {
> +		vcpu->arch.hcrx_el2 = HCRX_GUEST_FLAGS;
> +
> +		if (kvm_has_feat(kern_hyp_va(vcpu->kvm),

Not sure if the use of kern_hyp_va is intentional, seems out of place since we
use the bare `kvm` variable everyone else.

> +				 ID_AA64ISAR2_EL1, MOPS, IMP))
> +			vcpu->arch.hcrx_el2 |= (HCRX_EL2_MSCEn | HCRX_EL2_MCE2);
> +	}
> +
>  	if (test_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags))
>  		goto out;
>  

Thanks,
Joey