linux-kernel - Re: [PATCH v2 10/10] kvm: arm64: Remove unnecessary hyp mappings

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Date:   Thu, 10 Sep 2020 15:07:38 +0100
From:   Andrew Scull <ascull@...gle.com>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     Marc Zyngier <maz@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Dennis Zhou <dennis@...nel.org>,
        Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
        Arnd Bergmann <arnd@...db.de>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, linux-arch@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [PATCH v2 10/10] kvm: arm64: Remove unnecessary hyp mappings

On Thu, Sep 03, 2020 at 11:17:12AM +0200, 'David Brazdil' via kernel-team wrote:
> With all nVHE per-CPU variables being part of the hyp per-CPU region,
> mapping them individual is not necessary any longer. They are mapped to hyp
> as part of the overall per-CPU region.
> 
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>

Acked-by: Andrew Scull<ascull@...gle.com>

> ---
>  arch/arm64/include/asm/kvm_mmu.h | 25 +++++++------------------
>  arch/arm64/kvm/arm.c             | 17 +----------------
>  2 files changed, 8 insertions(+), 34 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index 9db93da35606..bbe9df76ff42 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -531,28 +531,17 @@ static inline int kvm_map_vectors(void)
>  DECLARE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
>  DECLARE_KVM_NVHE_PER_CPU(u64, arm64_ssbd_callback_required);
>  
> -static inline int hyp_init_aux_data(void)
> +static inline void hyp_init_aux_data(void)
>  {
> -	int cpu, err;
> +	int cpu;
>  
> -	for_each_possible_cpu(cpu) {
> -		u64 *ptr;
> -
> -		ptr = per_cpu_ptr_nvhe(arm64_ssbd_callback_required, cpu);
> -		err = create_hyp_mappings(ptr, ptr + 1, PAGE_HYP);
> -		if (err)
> -			return err;
> -
> -		/* Copy value from kernel to hyp. */
> -		*ptr = per_cpu(arm64_ssbd_callback_required, cpu);
> -	}
> -	return 0;
> +	/* Copy arm64_ssbd_callback_required values from kernel to hyp. */
> +	for_each_possible_cpu(cpu)
> +		*(per_cpu_ptr_nvhe(arm64_ssbd_callback_required, cpu)) =
> +			per_cpu(arm64_ssbd_callback_required, cpu);

Careful with breaking allocations across lines, that seems to be taboo
in this subsystem.

>  }
>  #else
> -static inline int hyp_init_aux_data(void)
> -{
> -	return 0;
> -}
> +static inline void hyp_init_aux_data(void) {}
>  #endif
>  
>  #define kvm_phys_to_vttbr(addr)		phys_to_ttbr(addr)
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index df7d133056ce..dfe1baa5bbb7 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1631,22 +1631,7 @@ static int init_hyp_mode(void)
>  		}
>  	}
>  
> -	for_each_possible_cpu(cpu) {
> -		kvm_host_data_t *cpu_data;
> -
> -		cpu_data = per_cpu_ptr_hyp(kvm_host_data, cpu);
> -		err = create_hyp_mappings(cpu_data, cpu_data + 1, PAGE_HYP);
> -
> -		if (err) {
> -			kvm_err("Cannot map host CPU state: %d\n", err);
> -			goto out_err;
> -		}
> -	}
> -
> -	err = hyp_init_aux_data();
> -	if (err)
> -		kvm_err("Cannot map host auxiliary data: %d\n", err);
> -
> +	hyp_init_aux_data();
>  	return 0;
>  
>  out_err:
> -- 
> 2.28.0.402.g5ffc5be6b7-goog
> 
> -- 
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>