linux-kernel - Re: [PATCH v3 04/20] kvm: arm64: Clean up VTCR

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Date:   Fri, 29 Jun 2018 16:50:48 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     cdall@...nel.org, kvm@...r.kernel.org, marc.zyngier@....com,
        catalin.marinas@....com, punit.agrawal@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        qemu-devel@...gnu.org, julien.grall@....com, james.morse@....com,
        kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH v3 04/20] kvm: arm64: Clean up VTCR_EL2 initialisation

Hi Suzuki,

On 06/29/2018 01:15 PM, Suzuki K Poulose wrote:
> Use the new helper for converting the parange to the physical shift.
> Also, add the missing definitions for the VTCR_EL2 register fields
> and use them instead of hard coding numbers.
> 
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Christoffer Dall <cdall@...nel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> Changes since V2
>  - Part 2 of the split from original patch.
>  - Also add missing VTCR field helpers and use them.
> ---
>  arch/arm64/include/asm/kvm_arm.h |  3 +++
>  arch/arm64/kvm/hyp/s2-setup.c    | 30 ++++++------------------------
>  2 files changed, 9 insertions(+), 24 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 6dd285e..3dffd38 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -106,6 +106,7 @@
>  #define VTCR_EL2_RES1		(1 << 31)
>  #define VTCR_EL2_HD		(1 << 22)
>  #define VTCR_EL2_HA		(1 << 21)
> +#define VTCR_EL2_PS_SHIFT	TCR_EL2_PS_SHIFT
>  #define VTCR_EL2_PS_MASK	TCR_EL2_PS_MASK
>  #define VTCR_EL2_TG0_MASK	TCR_TG0_MASK
>  #define VTCR_EL2_TG0_4K		TCR_TG0_4K
> @@ -126,6 +127,8 @@
>  #define VTCR_EL2_VS_8BIT	(0 << VTCR_EL2_VS_SHIFT)
>  #define VTCR_EL2_VS_16BIT	(1 << VTCR_EL2_VS_SHIFT)
>  
> +#define VTCR_EL2_T0SZ(x)	TCR_T0SZ(x)
> +
>  /*
>   * We configure the Stage-2 page tables to always restrict the IPA space to be
>   * 40 bits wide (T0SZ = 24).  Systems with a PARange smaller than 40 bits are
> diff --git a/arch/arm64/kvm/hyp/s2-setup.c b/arch/arm64/kvm/hyp/s2-setup.c
> index 603e1ee..81094f1 100644
> --- a/arch/arm64/kvm/hyp/s2-setup.c
> +++ b/arch/arm64/kvm/hyp/s2-setup.c
> @@ -19,11 +19,13 @@
>  #include <asm/kvm_arm.h>
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_hyp.h>
> +#include <asm/cpufeature.h>
>  
>  u32 __hyp_text __init_stage2_translation(void)
>  {
>  	u64 val = VTCR_EL2_FLAGS;
>  	u64 parange;
> +	u32 phys_shift;
>  	u64 tmp;

Not related to this patch but the comment reporting that bit 19 of
VTCR_EL2 is RES0 is not fully valid anymore as it now corresponds to
VMID size in ARM ARM >= 8.1.
>  
>  	/*
> @@ -34,30 +36,10 @@ u32 __hyp_text __init_stage2_translation(void)
>  	parange = read_sysreg(id_aa64mmfr0_el1) & 7;
>  	if (parange > ID_AA64MMFR0_PARANGE_MAX)
>  		parange = ID_AA64MMFR0_PARANGE_MAX;
> -	val |= parange << 16;
> +	val |= parange << VTCR_EL2_PS_SHIFT;
>  
>  	/* Compute the actual PARange... */
> -	switch (parange) {
> -	case 0:
> -		parange = 32;
> -		break;
> -	case 1:
> -		parange = 36;
> -		break;
> -	case 2:
> -		parange = 40;
> -		break;
> -	case 3:
> -		parange = 42;
> -		break;
> -	case 4:
> -		parange = 44;
> -		break;
> -	case 5:
> -	default:
> -		parange = 48;
> -		break;
> -	}
> +	phys_shift = id_aa64mmfr0_parange_to_phys_shift(parange);
>  
>  	/*
>  	 * ... and clamp it to 40 bits, unless we have some braindead
> @@ -65,7 +47,7 @@ u32 __hyp_text __init_stage2_translation(void)
>  	 * return that value for the rest of the kernel to decide what
>  	 * to do.
>  	 */
> -	val |= 64 - (parange > 40 ? 40 : parange);
> +	val |= VTCR_EL2_T0SZ(phys_shift > 40 ? 40 : phys_shift);
>  
>  	/*
>  	 * Check the availability of Hardware Access Flag / Dirty Bit
> @@ -86,5 +68,5 @@ u32 __hyp_text __init_stage2_translation(void)
>  
>  	write_sysreg(val, vtcr_el2);
>  
> -	return parange;
> +	return phys_shift;
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric

>  }
>