linux-kernel - Re: [PATCH v2 11/17] kvm: arm64: Configure VTCR per VM

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Date:   Thu, 3 May 2018 15:39:18 +0100
From:   James Morse <james.morse@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        cdall@...nel.org, marc.zyngier@....com, punit.agrawal@....com,
        will.deacon@....com, catalin.marinas@....com, pbonzini@...hat.com,
        rkrcmar@...hat.com, ard.biesheuvel@...aro.org,
        peter.maydell@...aro.org, kristina.martsenko@....com,
        mark.rutland@....com
Subject: Re: [PATCH v2 11/17] kvm: arm64: Configure VTCR per VM

Hi Suzuki,

On 27/03/18 14:15, Suzuki K Poulose wrote:
> We set VTCR_EL2 very early during the stage2 init and don't
> touch it ever. This is fine as we had a fixed IPA size. This
> patch changes the behavior to set the VTCR for a given VM,
> depending on its stage2 table. The common configuration for
> VTCR is still performed during the early init as we have to
> retain the hardware access flag update bits (VTCR_EL2_HA)
> per CPU (as they are only set for the CPUs which are capabile).
> The bits defining the number of levels in the page table (SL0)
> and and the size of the Input address to the translation (T0SZ)
> are programmed for each VM upon entry to the guest.


> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 596f8e4..9f3c8b8 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -392,10 +392,12 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
>  
>  static inline void __cpu_init_stage2(void)
>  {
> -	u32 parange = kvm_call_hyp(__init_stage2_translation);
> +	u32 ps;
>  
> -	WARN_ONCE(parange < 40,
> -		  "PARange is %d bits, unsupported configuration!", parange);
> +	kvm_call_hyp(__init_stage2_translation);
> +	ps = id_aa64mmfr0_parange_to_phys_shift(read_sysreg(id_aa64mmfr0_el1));

Doesn't id_aa64mmfr0_parange_to_phys_shift() expect you do to the mask and shift
for it? This will always hit the default case.


> +	WARN_ONCE(ps < 40,
> +		  "PARange is %d bits, unsupported configuration!", ps);
>  }



Thanks,

James