Re: [PATCH v1 3/3] KVM: arm64: Convert TCR_EL2 to config-driven sanitisation

[Marc Zyngier]

On Wed, 09 Sep 2026 23:20:15 +0100,
Wei-Lin Chang <weilin.chang@xxxxxxx> wrote:
> 
> Feature dependencies of the fields in TCR_EL2 are extracted from
> Registers.json of the BSD licenced AARCHMRS
> (AARCHMRS_OPENSOURCE_A_profile_FAT-2026-06).
> 
> Places where we slightly deviate from the above:
> 
>  - Stick to the ARM ARM M.c requirement for TCR_EL2.TCMA*, which only
>    depends on FEAT_MTE2. This avoids updating ID_AA64PFR2_EL1 with new
>    VMTE* definitions that we don't know the meaning of, as they aren't
>    present in the ARM ARM yet.
> 
>  - Ignore TCR_EL2.DS's requirement of needing the effective value of
>    TCR2_EL2.D128 be 0. This requires runtime detection of TCR2_EL2.D128
>    and we don't have D128 support yet.

The runtime stuff is never something we can do as part of the static
initialisation. I think the way this is captured in the JSON is a bit
hackish, and it should probably say:

IsFeatureImplemented(FEAT_LPA2) && (EffectiveValue(TCR2_EL2.D128) == '0')

which would naturally work.

> 
>  - TCR_EL2.AS is dependent on FEAT_ASID16, this information is missing
>    from the json.
> 
> Signed-off-by: Wei-Lin Chang <weilin.chang@xxxxxxx>
> ---
>  arch/arm64/include/asm/kvm_host.h |   2 +-
>  arch/arm64/kvm/config.c           | 113 ++++++++++++++++++++++++++++++
>  arch/arm64/kvm/nested.c           |   4 ++
>  3 files changed, 118 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 27fe0cd5b2d7..6a5e22ca3430 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -516,7 +516,6 @@ enum vcpu_sysreg {
>  	HACR_EL2,	/* Hypervisor Auxiliary Control Register */
>  	TTBR0_EL2,	/* Translation Table Base Register 0 (EL2) */
>  	TTBR1_EL2,	/* Translation Table Base Register 1 (EL2) */
> -	TCR_EL2,	/* Translation Control Register (EL2) */
>  	PIRE0_EL2,	/* Permission Indirection Register 0 (EL2) */
>  	PIR_EL2,	/* Permission Indirection Register 1 (EL2) */
>  	POR_EL2,	/* Permission Overlay Register 2 (EL2) */
> @@ -541,6 +540,7 @@ enum vcpu_sysreg {
>  	/* Anything from this can be RES0/RES1 sanitised */
>  	MARKER(__SANITISED_REG_START__),
>  	SCTLR_EL2,	/* System Control Register (EL2) */
> +	TCR_EL2,	/* Translation Control Register (EL2) */
>  	TCR2_EL2,	/* Extended Translation Control Register (EL2) */
>  	SCTLR2_EL2,	/* System Control Register 2 (EL2) */
>  	MDCR_EL2,	/* Monitor Debug Configuration Register (EL2) */
> diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
> index 1053676551af..3ccf5359a373 100644
> --- a/arch/arm64/kvm/config.c
> +++ b/arch/arm64/kvm/config.c
> @@ -203,8 +203,11 @@ struct reg_feat_map_desc {
>  #define FEAT_CPA2		ID_AA64ISAR3_EL1, CPA, CPA2
>  #define FEAT_ASID2		ID_AA64MMFR4_EL1, ASID2, IMP
>  #define FEAT_MEC		ID_AA64MMFR3_EL1, MEC, IMP
> +#define FEAT_HAF		ID_AA64MMFR1_EL1, HAFDBS, AF
>  #define FEAT_HAFT		ID_AA64MMFR1_EL1, HAFDBS, HAFT
> +#define FEAT_HAFDBS		ID_AA64MMFR1_EL1, HAFDBS, DBM
>  #define FEAT_HDBSS		ID_AA64MMFR1_EL1, HAFDBS, HDBSS
> +#define FEAT_HPDS		ID_AA64MMFR1_EL1, HPDS, IMP
>  #define FEAT_HPDS2		ID_AA64MMFR1_EL1, HPDS, HPDS2
>  #define FEAT_BTI		ID_AA64PFR1_EL1, BT, IMP
>  #define FEAT_ExS		ID_AA64MMFR0_EL1, EXS, IMP
> @@ -215,6 +218,10 @@ struct reg_feat_map_desc {
>  #define FEAT_MixedEndEL0	ID_AA64MMFR0_EL1, BIGENDEL0, IMP
>  #define FEAT_MTE_ASYNC		ID_AA64PFR1_EL1, MTE_frac, ASYNC
>  #define FEAT_MTE_STORE_ONLY	ID_AA64PFR2_EL1, MTESTOREONLY, IMP
> +#define FEAT_MTE_CANONICAL_TAGS	ID_AA64PFR1_EL1, MTEX, MTE4
> +#define FEAT_MTE_NO_ADDRESS_TAGS	ID_AA64PFR1_EL1, MTEX, MTE4
> +#define FEAT_E0PD		ID_AA64MMFR2_EL1, E0PD, IMP
> +#define FEAT_SVE		ID_AA64PFR0_EL1, SVE, IMP
>  #define FEAT_PAN		ID_AA64MMFR1_EL1, PAN, IMP
>  #define FEAT_PAN3		ID_AA64MMFR1_EL1, PAN, PAN3
>  #define FEAT_SSBS		ID_AA64PFR1_EL1, SSBS, IMP
> @@ -227,6 +234,19 @@ struct reg_feat_map_desc {
>  #define FEAT_GCIE		ID_AA64PFR2_EL1, GCIE, IMP
>  #define FEAT_NV3		ID_AA64MMFR4_EL1, NV_frac, NV3
>  
> +static bool feat_asid16(struct kvm *kvm)
> +{
> +	return kvm_has_feat_enum(kvm, ID_AA64MMFR0_EL1, ASIDBITS, 16);
> +}
> +
> +static bool feat_mte_no_addr_tags_or_canonical_tags(struct kvm *kvm)
> +{
> +	bool no_addr_tags = kvm_has_feat(kvm, FEAT_MTE_NO_ADDRESS_TAGS);
> +	bool canonical_tags = kvm_has_feat(kvm, FEAT_MTE_CANONICAL_TAGS);
> +
> +	return no_addr_tags || canonical_tags;
> +}
> +
>  static bool not_feat_aa64el3(struct kvm *kvm)
>  {
>  	return !kvm_has_feat(kvm, FEAT_AA64EL3);
> @@ -1044,6 +1064,91 @@ static const struct reg_bits_to_feat_map sctlr2_feat_map[] = {
>  static const DECLARE_FEAT_MAP(sctlr2_desc, SCTLR2_EL1,
>  			      sctlr2_feat_map, FEAT_SCTLR2);
>  
> +static const struct reg_bits_to_feat_map tcr_el2_vhe_feat_map[] = {

Maybe be consistent with the generated field names and call the array
'vhe_tcr_el2_feat_map'. Similarly for all the other names.

> +	NEEDS_FEAT(VHE_TCR_EL2_MTX1	|
> +		   VHE_TCR_EL2_MTX0,
> +		   feat_mte_no_addr_tags_or_canonical_tags),
> +	NEEDS_FEAT(VHE_TCR_EL2_DS, feat_lpa2),
> +	NEEDS_FEAT(VHE_TCR_EL2_TCMA1	|
> +		   VHE_TCR_EL2_TCMA0,
> +		   FEAT_MTE2),
> +	NEEDS_FEAT(VHE_TCR_EL2_E0PD1	|
> +		   VHE_TCR_EL2_E0PD0,
> +		   FEAT_E0PD),
> +	NEEDS_FEAT(VHE_TCR_EL2_NFD1	|
> +		   VHE_TCR_EL2_NFD0,
> +		   FEAT_SVE),
> +	NEEDS_FEAT(VHE_TCR_EL2_TBID1	|
> +		   VHE_TCR_EL2_TBID0,
> +		   feat_pauth),
> +	NEEDS_FEAT(VHE_TCR_EL2_HWU162	|
> +		   VHE_TCR_EL2_HWU161	|
> +		   VHE_TCR_EL2_HWU160	|
> +		   VHE_TCR_EL2_HWU159	|
> +		   VHE_TCR_EL2_HWU062	|
> +		   VHE_TCR_EL2_HWU061	|
> +		   VHE_TCR_EL2_HWU060	|
> +		   VHE_TCR_EL2_HWU059,
> +		   FEAT_HPDS2),
> +	NEEDS_FEAT(VHE_TCR_EL2_HPD1	|
> +		   VHE_TCR_EL2_HPD0,
> +		   FEAT_HPDS),
> +	NEEDS_FEAT(VHE_TCR_EL2_HD, FEAT_HAFDBS),
> +	NEEDS_FEAT(VHE_TCR_EL2_HA, FEAT_HAF),
> +	NEEDS_FEAT(VHE_TCR_EL2_AS, feat_asid16),
> +	NEEDS_FEAT(VHE_TCR_EL2_TBI1		|
> +		   VHE_TCR_EL2_TBI0		|
> +		   VHE_TCR_EL2_IPS		|
> +		   VHE_TCR_EL2_TG1		|
> +		   VHE_TCR_EL2_SH1		|
> +		   VHE_TCR_EL2_ORGN1		|
> +		   VHE_TCR_EL2_IRGN1		|
> +		   VHE_TCR_EL2_EPD1		|
> +		   VHE_TCR_EL2_A1		|
> +		   VHE_TCR_EL2_T1SZ		|
> +		   VHE_TCR_EL2_TG0		|
> +		   VHE_TCR_EL2_SH0		|
> +		   VHE_TCR_EL2_ORGN0		|
> +		   VHE_TCR_EL2_IRGN0		|
> +		   VHE_TCR_EL2_EPD0		|
> +		   VHE_TCR_EL2_T0SZ,
> +		   FEAT_AA64EL2),
> +	FORCE_RES0(VHE_TCR_EL2_RES0),
> +	FORCE_RES1(VHE_TCR_EL2_RES1),
> +};
> +
> +static const DECLARE_FEAT_MAP(tcr_el2_vhe_desc, VHE_TCR_EL2,
> +			      tcr_el2_vhe_feat_map, FEAT_AA64EL2);
> +
> +static const struct reg_bits_to_feat_map tcr_el2_nvhe_feat_map[] = {

and drop the nvhe here.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.