linux-kernel - Re: [PATCHv3 02/11] arm64/kvm: consistently handle host HCR

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Message-ID: <20180427095139.GH13249@C02W217FHV2R.local>
Date:   Fri, 27 Apr 2018 11:51:39 +0200
From:   Christoffer Dall <christoffer.dall@....com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-arch@...r.kernel.org,
        drjones@...hat.com, arnd@...db.de, suzuki.poulose@....com,
        marc.zyngier@....com, catalin.marinas@....com,
        awallis@...eaurora.org, kernel-hardening@...ts.openwall.com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        ramana.radhakrishnan@....com, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCHv3 02/11] arm64/kvm: consistently handle host HCR_EL2 flags

On Tue, Apr 17, 2018 at 07:37:26PM +0100, Mark Rutland wrote:
> In KVM we define the configuration of HCR_EL2 for a VHE HOST in
> HCR_HOST_VHE_FLAGS, but we don't ahve a similar definition for the

nit: have

> non-VHE host flags, and open-code HCR_RW. Further, in head.S we
> open-code the flags for VHE and non-VHE configurations.
> 
> In future, we're going to want to configure more flags for the host, so
> lets add a HCR_HOST_NVHE_FLAGS defintion, adn consistently use both

nit: and

> HCR_HOST_VHE_FLAGS and HCR_HOST_NVHE_FLAGS in the kvm code and head.S.
> 
> We now use mov_q to generate the HCR_EL2 value, as we use when
> configuring other registers in head.S.
> 
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Christoffer Dall <cdall@...nel.org>
> Cc: Marc Zyngier <marc.zyngier@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: kvmarm@...ts.cs.columbia.edu
> ---
>  arch/arm64/include/asm/kvm_arm.h | 1 +
>  arch/arm64/kernel/head.S         | 5 ++---
>  arch/arm64/kvm/hyp/switch.c      | 2 +-
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 6dd285e979c9..89b3dda7e3cb 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -86,6 +86,7 @@
>  			 HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW | HCR_TLOR | \
>  			 HCR_FMO | HCR_IMO)
>  #define HCR_VIRT_EXCP_MASK (HCR_VSE | HCR_VI | HCR_VF)
> +#define HCR_HOST_NVHE_FLAGS (HCR_RW)
>  #define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H)
>  
>  /* TCR_EL2 Registers bits */
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index b0853069702f..651a06b1980f 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -494,10 +494,9 @@ ENTRY(el2_setup)
>  #endif
>  
>  	/* Hyp configuration. */
> -	mov	x0, #HCR_RW			// 64-bit EL1
> +	mov_q	x0, HCR_HOST_NVHE_FLAGS
>  	cbz	x2, set_hcr
> -	orr	x0, x0, #HCR_TGE		// Enable Host Extensions
> -	orr	x0, x0, #HCR_E2H
> +	mov_q	x0, HCR_HOST_VHE_FLAGS
>  set_hcr:
>  	msr	hcr_el2, x0
>  	isb
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index d9645236e474..cdae330e15e9 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -143,7 +143,7 @@ static void __hyp_text __deactivate_traps_nvhe(void)
>  	mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT;
>  
>  	write_sysreg(mdcr_el2, mdcr_el2);
> -	write_sysreg(HCR_RW, hcr_el2);
> +	write_sysreg(HCR_HOST_NVHE_FLAGS, hcr_el2);
>  	write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
>  }
>  
> -- 
> 2.11.0
> 
> 
Reviewed-by: Christoffer Dall <christoffer.dall@....com>