Re: [PATCH] arm64: kvm: 4.6-rc1: Fix VTCR_EL2 VS setting

[Christoffer Dall <christoffer.dall@linaro.org>]

On Wed, Mar 30, 2016 at 02:33:59PM +0100, Suzuki K Poulose wrote:
> When we detect support for 16bit VMID in ID_AA64MMFR1, we set the
> VTCR_EL2_VS field to 1 to make use of 16bit vmids. But, with
> commit 3a3604bc5eb4 ("arm64: KVM: Switch to C-based stage2 init")
> this is broken and we corrupt VTCR_EL2:T0SZ instead of updating the VS
> field. VTCR_EL2_VS was actually defined to the field shift (19) and
> not the real value for VS. This patch fixes the issue.
> 
> Fixes: commit 3a3604bc5eb4 ("arm64: KVM: Switch to C-based stage2 init")
> Cc: Christoffer Dall <christoffer.dall@linaro.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>

Acked-by: Christoffer Dall <christoffer.dall@linaro.org>

> ---
>  arch/arm64/include/asm/kvm_arm.h |    4 +++-
>  arch/arm64/include/asm/sysreg.h  |    3 +++
>  arch/arm64/kvm/hyp/s2-setup.c    |    6 ++++--
>  3 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 0e391db..4150fd8 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -124,7 +124,9 @@
>  #define VTCR_EL2_SL0_LVL1	(1 << 6)
>  #define VTCR_EL2_T0SZ_MASK	0x3f
>  #define VTCR_EL2_T0SZ_40B	24
> -#define VTCR_EL2_VS		19
> +#define VTCR_EL2_VS_SHIFT	19
> +#define VTCR_EL2_VS_8BIT	(0 << VTCR_EL2_VS_SHIFT)
> +#define VTCR_EL2_VS_16BIT	(1 << VTCR_EL2_VS_SHIFT)
>  
>  /*
>   * We configure the Stage-2 page tables to always restrict the IPA space to be
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 1a78d6e..1287416 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -141,6 +141,9 @@
>  #define ID_AA64MMFR1_VMIDBITS_SHIFT	4
>  #define ID_AA64MMFR1_HADBS_SHIFT	0
>  
> +#define ID_AA64MMFR1_VMIDBITS_8		0
> +#define ID_AA64MMFR1_VMIDBITS_16	2
> +
>  /* id_aa64mmfr2 */
>  #define ID_AA64MMFR2_UAO_SHIFT		4
>  
> diff --git a/arch/arm64/kvm/hyp/s2-setup.c b/arch/arm64/kvm/hyp/s2-setup.c
> index bfc54fd..5a9f3bf 100644
> --- a/arch/arm64/kvm/hyp/s2-setup.c
> +++ b/arch/arm64/kvm/hyp/s2-setup.c
> @@ -36,8 +36,10 @@ void __hyp_text __init_stage2_translation(void)
>  	 * Read the VMIDBits bits from ID_AA64MMFR1_EL1 and set the VS
>  	 * bit in VTCR_EL2.
>  	 */
> -	tmp = (read_sysreg(id_aa64mmfr1_el1) >> 4) & 0xf;
> -	val |= (tmp == 2) ? VTCR_EL2_VS : 0;
> +	tmp = (read_sysreg(id_aa64mmfr1_el1) >> ID_AA64MMFR1_VMIDBITS_SHIFT) & 0xf;
> +	val |= (tmp == ID_AA64MMFR1_VMIDBITS_16) ?
> +			VTCR_EL2_VS_16BIT :
> +			VTCR_EL2_VS_8BIT;
>  
>  	write_sysreg(val, vtcr_el2);
>  }
> -- 
> 1.7.9.5
>