Re: [PATCH 20/59] KVM: arm64: nv: Trap CPACR_EL1 access in virtual EL2

From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org
Cc: Andre Przywara <andre.przywara@arm.com>,
	Dave Martin <Dave.Martin@arm.com>
Subject: Re: [PATCH 20/59] KVM: arm64: nv: Trap CPACR_EL1 access in virtual EL2
Date: Mon, 1 Jul 2019 17:40:13 +0100	[thread overview]
Message-ID: <a7b309a6-83c1-27cc-f587-17389ccfd857@arm.com> (raw)
In-Reply-To: <20190621093843.220980-21-marc.zyngier@arm.com>


On 6/21/19 10:38 AM, Marc Zyngier wrote:
> From: Jintack Lim <jintack.lim@linaro.org>
>
> For the same reason we trap virtual memory register accesses in virtual
> EL2, we trap CPACR_EL1 access too; We allow the virtual EL2 mode to
> access EL1 system register state instead of the virtual EL2 one.
>
> Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  arch/arm64/include/asm/kvm_arm.h | 3 ++-
>  arch/arm64/kvm/hyp/switch.c      | 2 ++
>  arch/arm64/kvm/sys_regs.c        | 2 +-
>  3 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index b2e363ac624d..48e15af2bece 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -278,12 +278,13 @@
>  #define CPTR_EL2_TFP_SHIFT 10
>  
>  /* Hyp Coprocessor Trap Register */
> -#define CPTR_EL2_TCPAC	(1 << 31)
> +#define CPTR_EL2_TCPAC	(1U << 31)
>  #define CPTR_EL2_TTA	(1 << 20)
>  #define CPTR_EL2_TFP	(1 << CPTR_EL2_TFP_SHIFT)
>  #define CPTR_EL2_TZ	(1 << 8)
>  #define CPTR_EL2_RES1	0x000032ff /* known RES1 bits in CPTR_EL2 */
>  #define CPTR_EL2_DEFAULT	CPTR_EL2_RES1
> +#define CPTR_EL2_E2H_TCPAC	(1U << 31)
I'm not sure why CPTR_EL2_TCPAC is being renamed to CPTR_EL2_E2H_TCPAC.
CPTR_EL2.TCPAC is always bit 31, regardless of the value of HCR_EL2.E2H. I also
did a grep and it's only used in the one place added by this patch.
>  
>  /* Hyp Debug Configuration Register bits */
>  #define MDCR_EL2_TPMS		(1 << 14)
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 791b26570347..62359c7c3d6b 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -108,6 +108,8 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
>  		val &= ~CPACR_EL1_FPEN;
>  		__activate_traps_fpsimd32(vcpu);
>  	}
> +	if (vcpu_mode_el2(vcpu) && !vcpu_el2_e2h_is_set(vcpu))
> +		val |= CPTR_EL2_E2H_TCPAC;
>  
>  	write_sysreg(val, cpacr_el1);
>  
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 7fc87657382d..1d1312425cf2 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1773,7 +1773,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	ID_UNALLOCATED(7,7),
>  
>  	{ SYS_DESC(SYS_SCTLR_EL1), access_vm_reg, reset_val, SCTLR_EL1, 0x00C50078 },
> -	{ SYS_DESC(SYS_CPACR_EL1), NULL, reset_val, CPACR_EL1, 0 },
> +	{ SYS_DESC(SYS_CPACR_EL1), access_rw, reset_val, CPACR_EL1, 0 },
>  	{ SYS_DESC(SYS_ZCR_EL1), NULL, reset_val, ZCR_EL1, 0, .visibility = sve_visibility },
>  	{ SYS_DESC(SYS_TTBR0_EL1), access_vm_reg, reset_unknown, TTBR0_EL1 },
>  	{ SYS_DESC(SYS_TTBR1_EL1), access_vm_reg, reset_unknown, TTBR1_EL1 },
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