linux-kernel - Re: [PATCH] KVM: arm64: Use the bitmap API to allocate bitmaps

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Message-ID: <33aafc05-daa1-50e0-00ab-dab97bb8a879@arm.com>
Date:   Wed, 6 Jul 2022 10:20:05 +0100
From:   Vladimir Murzin <vladimir.murzin@....com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu
Subject: Re: [PATCH] KVM: arm64: Use the bitmap API to allocate bitmaps

On 7/4/22 20:10, Christophe JAILLET wrote:
> Use bitmap_zalloc()/bitmap_free() instead of hand-writing them.
> 
> It is less verbose and it improves the semantic.
> 
> While at it, turn a bitmap_clear() into an equivalent bitmap_zero(). It is
> also less verbose.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
>  arch/arm64/kvm/vmid.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/kvm/vmid.c b/arch/arm64/kvm/vmid.c
> index d78ae63d7c15..f4612cdb60ff 100644
> --- a/arch/arm64/kvm/vmid.c
> +++ b/arch/arm64/kvm/vmid.c
> @@ -47,7 +47,7 @@ static void flush_context(void)
>  	int cpu;
>  	u64 vmid;
>  
> -	bitmap_clear(vmid_map, 0, NUM_USER_VMIDS);
> +	bitmap_zero(vmid_map, NUM_USER_VMIDS);
>  
>  	for_each_possible_cpu(cpu) {
>  		vmid = atomic64_xchg_relaxed(&per_cpu(active_vmids, cpu), 0);
> @@ -182,8 +182,7 @@ int kvm_arm_vmid_alloc_init(void)
>  	 */
>  	WARN_ON(NUM_USER_VMIDS - 1 <= num_possible_cpus());
>  	atomic64_set(&vmid_generation, VMID_FIRST_VERSION);
> -	vmid_map = kcalloc(BITS_TO_LONGS(NUM_USER_VMIDS),
> -			   sizeof(*vmid_map), GFP_KERNEL);
> +	vmid_map = bitmap_zalloc(NUM_USER_VMIDS, GFP_KERNEL);
>  	if (!vmid_map)
>  		return -ENOMEM;
>  
> @@ -192,5 +191,5 @@ int kvm_arm_vmid_alloc_init(void)
>  
>  void kvm_arm_vmid_alloc_free(void)
>  {
> -	kfree(vmid_map);
> +	bitmap_free(vmid_map);
>  }

FWIW

Reviewed-by: Vladimir Murzin <vladimir.murzin@....com>

Cheers
Vladimir