Re: [PATCH 3/4] KVM: arm64: Convert the host S2 over to __load_guest_stage2()

From: Quentin Perret <qperret@google.com>
To: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org, kernel-team@android.com,
	Catalin Marinas <catalin.marinas@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Jade Alglave <jade.alglave@arm.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
	kvmarm@lists.cs.columbia.edu, linux-arch@vger.kernel.org
Subject: Re: [PATCH 3/4] KVM: arm64: Convert the host S2 over to __load_guest_stage2()
Date: Fri, 6 Aug 2021 14:40:00 +0100	[thread overview]
Message-ID: <YQ07sPoa4ACizYrp@google.com> (raw)
In-Reply-To: <20210806113109.2475-5-will@kernel.org>

On Friday 06 Aug 2021 at 12:31:07 (+0100), Will Deacon wrote:
> From: Marc Zyngier <maz@kernel.org>
> 
> The protected mode relies on a separate helper to load the
> S2 context. Move over to the __load_guest_stage2() helper
> instead.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Jade Alglave <jade.alglave@arm.com>
> Cc: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/include/asm/kvm_mmu.h              | 11 +++--------
>  arch/arm64/kvm/hyp/include/nvhe/mem_protect.h |  2 +-
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c         |  2 +-
>  3 files changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 05e089653a1a..934ef0deff9f 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -267,9 +267,10 @@ static __always_inline u64 kvm_get_vttbr(struct kvm_s2_mmu *mmu)
>   * Must be called from hyp code running at EL2 with an updated VTTBR
>   * and interrupts disabled.
>   */
> -static __always_inline void __load_stage2(struct kvm_s2_mmu *mmu, unsigned long vtcr)
> +static __always_inline void __load_guest_stage2(struct kvm_s2_mmu *mmu,
> +						struct kvm_arch *arch)
>  {
> -	write_sysreg(vtcr, vtcr_el2);
> +	write_sysreg(arch->vtcr, vtcr_el2);
>  	write_sysreg(kvm_get_vttbr(mmu), vttbr_el2);
>  
>  	/*
> @@ -280,12 +281,6 @@ static __always_inline void __load_stage2(struct kvm_s2_mmu *mmu, unsigned long
>  	asm(ALTERNATIVE("nop", "isb", ARM64_WORKAROUND_SPECULATIVE_AT));
>  }
>  
> -static __always_inline void __load_guest_stage2(struct kvm_s2_mmu *mmu,
> -						struct kvm_arch *arch)
> -{
> -	__load_stage2(mmu, arch->vtcr);
> -}
> -
>  static inline struct kvm *kvm_s2_mmu_to_kvm(struct kvm_s2_mmu *mmu)
>  {
>  	return container_of(mmu->arch, struct kvm, arch);
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> index 9c227d87c36d..a910648bc71b 100644
> --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
> @@ -29,7 +29,7 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt);
>  static __always_inline void __load_host_stage2(void)
>  {
>  	if (static_branch_likely(&kvm_protected_mode_initialized))
> -		__load_stage2(&host_kvm.arch.mmu, host_kvm.arch.vtcr);
> +		__load_guest_stage2(&host_kvm.arch.mmu, &host_kvm.arch);
>  	else
>  		write_sysreg(0, vttbr_el2);
>  }
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index d938ce95d3bd..d4e74ca7f876 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -126,7 +126,7 @@ int __pkvm_prot_finalize(void)
>  	kvm_flush_dcache_to_poc(params, sizeof(*params));
>  
>  	write_sysreg(params->hcr_el2, hcr_el2);
> -	__load_stage2(&host_kvm.arch.mmu, host_kvm.arch.vtcr);
> +	__load_guest_stage2(&host_kvm.arch.mmu, &host_kvm.arch);

Nit: clearly we're not loading a guest stage-2 here, so maybe the
function should take a more generic name?

Thanks,
Quentin