linux-kernel - Re: [PATCH V2] KVM: arm64: Implement vq

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Date:   Mon, 10 Jun 2019 10:56:00 +0100
From:   Dave Martin <Dave.Martin@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V2] KVM: arm64: Implement vq_present() as a macro

On Mon, Jun 10, 2019 at 03:20:30PM +0530, Viresh Kumar wrote:
> On 10-06-19, 10:09, Dave Martin wrote:
> > You could drop the extra level of indirection on vqs now.  The only
> > thing it achieves is to enforce the size of the array via type-
> > checkout, but the macro can't easily do that (unless you can think
> > of another way to do it).
> > 
> > Otherwise, looks good.
> 
> Below is what I wrote initially this morning and then moved to the
> current version as I wasn't sure if you would want that :)
> 
> -- 
> viresh
> 
> -------------------------8<-------------------------
> 
> From be823e68faffc82a6f621c16ce1bd45990d92791 Mon Sep 17 00:00:00 2001
> Message-Id: <be823e68faffc82a6f621c16ce1bd45990d92791.1560160165.git.viresh.kumar@...aro.org>
> From: Viresh Kumar <viresh.kumar@...aro.org>
> Date: Mon, 10 Jun 2019 11:15:17 +0530
> Subject: [PATCH] KVM: arm64: Implement vq_present() as a macro
> 
> This routine is a one-liner and doesn't really need to be function and
> can be implemented as a macro.
> 
> Suggested-by: Dave Martin <Dave.Martin@....com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  arch/arm64/kvm/guest.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 3ae2f82fca46..ae734fcfd4ea 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -207,13 +207,7 @@ static int set_core_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  
>  #define vq_word(vq) (((vq) - SVE_VQ_MIN) / 64)
>  #define vq_mask(vq) ((u64)1 << ((vq) - SVE_VQ_MIN) % 64)
> -
> -static bool vq_present(
> -	const u64 (*const vqs)[KVM_ARM64_SVE_VLS_WORDS],
> -	unsigned int vq)
> -{
> -	return (*vqs)[vq_word(vq)] & vq_mask(vq);
> -}
> +#define vq_present(vqs, vq) ((vqs)[vq_word(vq)] & vq_mask(vq))
>  
>  static int get_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  {
> @@ -258,7 +252,7 @@ static int set_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  
>  	max_vq = 0;
>  	for (vq = SVE_VQ_MIN; vq <= SVE_VQ_MAX; ++vq)
> -		if (vq_present(&vqs, vq))
> +		if (vq_present(vqs, vq))
>  			max_vq = vq;
>  
>  	if (max_vq > sve_vq_from_vl(kvm_sve_max_vl))
> @@ -272,7 +266,7 @@ static int set_sve_vls(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
>  	 * maximum:
>  	 */
>  	for (vq = SVE_VQ_MIN; vq <= max_vq; ++vq)
> -		if (vq_present(&vqs, vq) != sve_vq_available(vq))
> +		if (vq_present(vqs, vq) != sve_vq_available(vq))
>  			return -EINVAL;

I think I prefer this version:

Reviewed-by: Dave Martin <Dave.Martin@....com>

Cheers
---Dave