[PATCH v2 13/26] KVM: arm64: Restructure FGT register switching

[Miguel Luis]

Hi Marc,

> On 28 Jul 2023, at 08:29, Marc Zyngier <maz at kernel.org> wrote:
> 
> As we're about to majorly extend the handling of FGT registers,
> restructure the code to actually save/restore the registers
> as required. This is made easy thanks to the previous addition
> of the EL2 registers, allowing us to use the host context for
> this purpose.
> 
> Signed-off-by: Marc Zyngier <maz at kernel.org>
> ---
> arch/arm64/include/asm/kvm_arm.h        | 21 ++++++++++
> arch/arm64/kvm/hyp/include/hyp/switch.h | 56 +++++++++++++------------
> 2 files changed, 50 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 028049b147df..85908aa18908 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -333,6 +333,27 @@
> BIT(18) | \
> GENMASK(16, 15))
> 
> +/*
> + * FGT register definitions
> + *
> + * RES0 and polarity masks as of DDI0487J.a, to be updated as needed.
> + * We're not using the generated masks as they are usually ahead of
> + * the published ARM ARM, which we use as a reference.
> + *
> + * Once we get to a point where the two describe the same thing, we'll
> + * merge the definitions. One day.
> + */
> +#define __HFGRTR_EL2_RES0 (GENMASK(63, 56) | GENMASK(53, 51))
> +#define __HFGRTR_EL2_MASK GENMASK(49, 0)
> +#define __HFGRTR_EL2_nMASK (GENMASK(55, 54) | BIT(50))
> +
> +#define __HFGWTR_EL2_RES0 (GENMASK(63, 56) | GENMASK(53, 51) | \
> + BIT(46) | BIT(42) | BIT(40) | BIT(28) | \
> + GENMASK(26, 25) | BIT(21) | BIT(18) | \
> + GENMASK(15, 14) | GENMASK(10, 9) | BIT(2))
> +#define __HFGWTR_EL2_MASK GENMASK(49, 0)
> +#define __HFGWTR_EL2_nMASK (GENMASK(55, 54) | BIT(50))
> +
> /* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
> #define HPFAR_MASK (~UL(0xf))
> /*
> diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
> index 4bddb8541bec..966295178aee 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/switch.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
> @@ -70,20 +70,19 @@ static inline void __activate_traps_fpsimd32(struct kvm_vcpu *vcpu)
> }
> }
> 
> -static inline bool __hfgxtr_traps_required(void)
> -{
> - if (cpus_have_final_cap(ARM64_SME))
> - return true;
> -
> - if (cpus_have_final_cap(ARM64_WORKAROUND_AMPERE_AC03_CPU_38))
> - return true;
> 
> - return false;
> -}
> 
> -static inline void __activate_traps_hfgxtr(void)
> +static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
> {
> + struct kvm_cpu_context *hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> u64 r_clr = 0, w_clr = 0, r_set = 0, w_set = 0, tmp;
> + u64 r_val, w_val;
> +
> + if (!cpus_have_final_cap(ARM64_HAS_FGT))
> + return;
> +
> + ctxt_sys_reg(hctxt, HFGRTR_EL2) = read_sysreg_s(SYS_HFGRTR_EL2);
> + ctxt_sys_reg(hctxt, HFGWTR_EL2) = read_sysreg_s(SYS_HFGWTR_EL2);
> 
> if (cpus_have_final_cap(ARM64_SME)) {
> tmp = HFGxTR_EL2_nSMPRI_EL1_MASK | HFGxTR_EL2_nTPIDR2_EL0_MASK;
> @@ -98,26 +97,31 @@ static inline void __activate_traps_hfgxtr(void)
> if (cpus_have_final_cap(ARM64_WORKAROUND_AMPERE_AC03_CPU_38))
> w_set |= HFGxTR_EL2_TCR_EL1_MASK;
> 
> - sysreg_clear_set_s(SYS_HFGRTR_EL2, r_clr, r_set);
> - sysreg_clear_set_s(SYS_HFGWTR_EL2, w_clr, w_set);
> +
> + /* The default is not to trap amything but ACCDATA_EL1 */
> + r_val = __HFGRTR_EL2_nMASK & ~HFGxTR_EL2_nACCDATA_EL1;
> + r_val |= r_set;
> + r_val &= ~r_clr;
> +
> + w_val = __HFGWTR_EL2_nMASK & ~HFGxTR_EL2_nACCDATA_EL1;
> + w_val |= w_set;
> + w_val &= ~w_clr;
> +
> + write_sysreg_s(r_val, SYS_HFGRTR_EL2);
> + write_sysreg_s(w_val, SYS_HFGWTR_EL2);
> }
> 
> -static inline void __deactivate_traps_hfgxtr(void)
> +static inline void __deactivate_traps_hfgxtr(struct kvm_vcpu *vcpu)
> {
> - u64 r_clr = 0, w_clr = 0, r_set = 0, w_set = 0, tmp;
> + struct kvm_cpu_context *hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> 
> - if (cpus_have_final_cap(ARM64_SME)) {
> - tmp = HFGxTR_EL2_nSMPRI_EL1_MASK | HFGxTR_EL2_nTPIDR2_EL0_MASK;
> + if (!cpus_have_final_cap(ARM64_HAS_FGT))
> + return;
> 
> - r_set |= tmp;
> - w_set |= tmp;
> - }
> + write_sysreg_s(ctxt_sys_reg(hctxt, HFGRTR_EL2), SYS_HFGRTR_EL2);
> + write_sysreg_s(ctxt_sys_reg(hctxt, HFGWTR_EL2), SYS_HFGWTR_EL2);
> 
> - if (cpus_have_final_cap(ARM64_WORKAROUND_AMPERE_AC03_CPU_38))
> - w_clr |= HFGxTR_EL2_TCR_EL1_MASK;
> 
> - sysreg_clear_set_s(SYS_HFGRTR_EL2, r_clr, r_set);
> - sysreg_clear_set_s(SYS_HFGWTR_EL2, w_clr, w_set);
> }
> 
> static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
> @@ -145,8 +149,7 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
> vcpu->arch.mdcr_el2_host = read_sysreg(mdcr_el2);
> write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
> 
> - if (__hfgxtr_traps_required())
> - __activate_traps_hfgxtr();
> + __activate_traps_hfgxtr(vcpu);
> }
> 
> static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
> @@ -162,8 +165,7 @@ static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
> vcpu_clear_flag(vcpu, PMUSERENR_ON_CPU);
> }
> 
> - if (__hfgxtr_traps_required())
> - __deactivate_traps_hfgxtr();
> + __deactivate_traps_hfgxtr(vcpu);

Reviewed-by: Miguel Luis <miguel.luis at oracle.com>

Thanks

Miguel

> }
> 
> static inline void ___activate_traps(struct kvm_vcpu *vcpu)
> -- 
> 2.34.1
>