Re: [PATCH v5 18/37] KVM: arm64: Add AT fast-path support for S1PIE

[Joey Gouly <joey.gouly@arm.com>]

On Wed, Oct 23, 2024 at 03:53:26PM +0100, Marc Zyngier wrote:
> Emulating AT using AT instructions requires that the live state
> matches the translation regime the AT instruction targets.
> 
> If targeting the EL1&0 translation regime and that S1PIE is
> supported, we also need to restore that state (covering TCR2_EL1,
> PIR_EL1, and PIRE0_EL1).
> 
> Add the required system register switcheroo.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>

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

> ---
>  arch/arm64/kvm/at.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
> index f04677127fbc0..b9d0992e91972 100644
> --- a/arch/arm64/kvm/at.c
> +++ b/arch/arm64/kvm/at.c
> @@ -412,6 +412,9 @@ struct mmu_config {
>  	u64	ttbr1;
>  	u64	tcr;
>  	u64	mair;
> +	u64	tcr2;
> +	u64	pir;
> +	u64	pire0;
>  	u64	sctlr;
>  	u64	vttbr;
>  	u64	vtcr;
> @@ -424,6 +427,13 @@ static void __mmu_config_save(struct mmu_config *config)
>  	config->ttbr1	= read_sysreg_el1(SYS_TTBR1);
>  	config->tcr	= read_sysreg_el1(SYS_TCR);
>  	config->mair	= read_sysreg_el1(SYS_MAIR);
> +	if (cpus_have_final_cap(ARM64_HAS_TCR2)) {
> +		config->tcr2	= read_sysreg_el1(SYS_TCR2);
> +		if (cpus_have_final_cap(ARM64_HAS_S1PIE)) {
> +			config->pir	= read_sysreg_el1(SYS_PIR);
> +			config->pire0	= read_sysreg_el1(SYS_PIRE0);
> +		}
> +	}
>  	config->sctlr	= read_sysreg_el1(SYS_SCTLR);
>  	config->vttbr	= read_sysreg(vttbr_el2);
>  	config->vtcr	= read_sysreg(vtcr_el2);
> @@ -444,6 +454,13 @@ static void __mmu_config_restore(struct mmu_config *config)
>  	write_sysreg_el1(config->ttbr1,	SYS_TTBR1);
>  	write_sysreg_el1(config->tcr,	SYS_TCR);
>  	write_sysreg_el1(config->mair,	SYS_MAIR);
> +	if (cpus_have_final_cap(ARM64_HAS_TCR2)) {
> +		write_sysreg_el1(config->tcr2, SYS_TCR2);
> +		if (cpus_have_final_cap(ARM64_HAS_S1PIE)) {
> +			write_sysreg_el1(config->pir, SYS_PIR);
> +			write_sysreg_el1(config->pire0, SYS_PIRE0);
> +		}
> +	}
>  	write_sysreg_el1(config->sctlr,	SYS_SCTLR);
>  	write_sysreg(config->vttbr,	vttbr_el2);
>  	write_sysreg(config->vtcr,	vtcr_el2);
> @@ -914,6 +931,13 @@ static u64 __kvm_at_s1e01_fast(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
>  	write_sysreg_el1(vcpu_read_sys_reg(vcpu, TTBR1_EL1),	SYS_TTBR1);
>  	write_sysreg_el1(vcpu_read_sys_reg(vcpu, TCR_EL1),	SYS_TCR);
>  	write_sysreg_el1(vcpu_read_sys_reg(vcpu, MAIR_EL1),	SYS_MAIR);
> +	if (kvm_has_feat(vcpu->kvm, ID_AA64MMFR3_EL1, TCRX, IMP)) {
> +		write_sysreg_el1(vcpu_read_sys_reg(vcpu, TCR2_EL1), SYS_TCR2);
> +		if (kvm_has_feat(vcpu->kvm, ID_AA64MMFR3_EL1, S1PIE, IMP)) {
> +			write_sysreg_el1(vcpu_read_sys_reg(vcpu, PIR_EL1), SYS_PIR);
> +			write_sysreg_el1(vcpu_read_sys_reg(vcpu, PIRE0_EL1), SYS_PIRE0);
> +		}
> +	}
>  	write_sysreg_el1(vcpu_read_sys_reg(vcpu, SCTLR_EL1),	SYS_SCTLR);
>  	__load_stage2(mmu, mmu->arch);
>