Re: [PATCH v2 7/7] KVM: arm64: Consolidate initializing the host data's fpsimd_state/sve in pKVM

From: Marc Zyngier <maz@kernel.org>
To: Fuad Tabba <tabba@google.com>
Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	will@kernel.org, qperret@google.com, seanjc@google.com,
	alexandru.elisei@arm.com, catalin.marinas@arm.com,
	philmd@linaro.org, james.morse@arm.com, suzuki.poulose@arm.com,
	oliver.upton@linux.dev, mark.rutland@arm.com, broonie@kernel.org,
	joey.gouly@arm.com, rananta@google.com, yuzenghui@huawei.com
Subject: Re: [PATCH v2 7/7] KVM: arm64: Consolidate initializing the host data's fpsimd_state/sve in pKVM
Date: Tue, 21 May 2024 23:55:55 +0100	[thread overview]
Message-ID: <86msoin5ac.wl-maz@kernel.org> (raw)
In-Reply-To: <20240521163720.3812851-8-tabba@google.com>

On Tue, 21 May 2024 17:37:20 +0100,
Fuad Tabba <tabba@google.com> wrote:
> 
> Now that we have introduced finalize_init_hyp_mode(), lets
> consolidate the initializing of the host_data fpsimd_state and
> sve state.
> 
> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---
>  arch/arm64/include/asm/kvm_host.h      | 10 ++++++++--
>  arch/arm64/kvm/arm.c                   | 18 ++++++++++++------
>  arch/arm64/kvm/hyp/include/nvhe/pkvm.h |  1 -
>  arch/arm64/kvm/hyp/nvhe/pkvm.c         | 11 -----------
>  arch/arm64/kvm/hyp/nvhe/setup.c        |  1 -
>  5 files changed, 20 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 7b3745ef1d73..8a170f314498 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -536,8 +536,14 @@ struct kvm_cpu_context {
>  struct kvm_host_data {
>  	struct kvm_cpu_context host_ctxt;
>  
> -	struct user_fpsimd_state *fpsimd_state;	/* hyp VA */
> -	struct user_sve_state *sve_state;	/* hyp VA */
> +	/*
> +	 * All pointers in this union are hyp VA.
> +	 * sve_state is only used in pKVM and if system_supports_sve().
> +	 */
> +	union {
> +		struct user_fpsimd_state *fpsimd_state;
> +		struct user_sve_state *sve_state;
> +	};
>  
>  	/* Ownership of the FP regs */
>  	enum {
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index a9b1b0e9c319..a1c7e0ad6951 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -2445,14 +2445,20 @@ static void finalize_init_hyp_mode(void)
>  {
>  	int cpu;
>  
> -	if (!is_protected_kvm_enabled() || !system_supports_sve())
> -		return;
> -
>  	for_each_possible_cpu(cpu) {
> -		struct user_sve_state *sve_state;
> +		if (system_supports_sve() && is_protected_kvm_enabled()) {
> +			struct user_sve_state *sve_state;
>  
> -		sve_state = per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->sve_state;
> -		per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->sve_state = kern_hyp_va(sve_state);
> +			sve_state = per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->sve_state;
> +			per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->sve_state =
> +				kern_hyp_va(sve_state);
> +		} else {
> +			struct user_fpsimd_state *fpsimd_state;
> +
> +			fpsimd_state = &per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->host_ctxt.fp_regs;
> +			per_cpu_ptr_nvhe_sym(kvm_host_data, cpu)->fpsimd_state =
> +				kern_hyp_va(fpsimd_state);
> +		}

nit: SVE support and protected state do not change on a per CPU basis,
so checking for these inside the loop is pretty counter intuitive.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.