linux-kernel - Re: [PATCH] LoongArch: KVM: Remove redundant assignment in kvm_map_page

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Message-ID: <286be0a6-dac3-b2cd-e88a-e6feb5a240de@loongson.cn>
Date: Fri, 26 Jul 2024 10:13:19 +0800
From: maobibo <maobibo@...ngson.cn>
To: tangbin <tangbin@...s.chinamobile.com>, zhaotianrui@...ngson.cn,
 chenhuacai@...nel.org, kernel@...0n.name
Cc: kvm@...r.kernel.org, loongarch@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] LoongArch: KVM: Remove redundant assignment in
 kvm_map_page_fast

Hi Tangbin,

There is only return value with -EFAULT or 0 in function 
kvm_map_page_fast(), if there is better error code or different error 
for new code, the situation will be different :)

I would like to keep existing code unchanged, however thanks for your patch.

Regards
Bibo Mao

On 2024/7/13 下午11:59, tangbin wrote:
> In the function kvm_map_page_fast, the assignment of 'ret' is
> redundant, so remove it.
> 
> Signed-off-by: tangbin <tangbin@...s.chinamobile.com>
> ---
>   arch/loongarch/kvm/mmu.c | 17 +++++------------
>   1 file changed, 5 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/loongarch/kvm/mmu.c b/arch/loongarch/kvm/mmu.c
> index 2634a9e8d..d6c922a4a 100644
> --- a/arch/loongarch/kvm/mmu.c
> +++ b/arch/loongarch/kvm/mmu.c
> @@ -551,7 +551,6 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
>    */
>   static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool write)
>   {
> -	int ret = 0;
>   	kvm_pfn_t pfn = 0;
>   	kvm_pte_t *ptep, changed, new;
>   	gfn_t gfn = gpa >> PAGE_SHIFT;
> @@ -563,20 +562,16 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
>   
>   	/* Fast path - just check GPA page table for an existing entry */
>   	ptep = kvm_populate_gpa(kvm, NULL, gpa, 0);
> -	if (!ptep || !kvm_pte_present(NULL, ptep)) {
> -		ret = -EFAULT;
> +	if (!ptep || !kvm_pte_present(NULL, ptep))
>   		goto out;
> -	}
>   
>   	/* Track access to pages marked old */
>   	new = kvm_pte_mkyoung(*ptep);
>   	/* call kvm_set_pfn_accessed() after unlock */
>   
>   	if (write && !kvm_pte_dirty(new)) {
> -		if (!kvm_pte_write(new)) {
> -			ret = -EFAULT;
> +		if (!kvm_pte_write(new))
>   			goto out;
> -		}
>   
>   		if (kvm_pte_huge(new)) {
>   			/*
> @@ -584,10 +579,8 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
>   			 * enabled for HugePages
>   			 */
>   			slot = gfn_to_memslot(kvm, gfn);
> -			if (kvm_slot_dirty_track_enabled(slot)) {
> -				ret = -EFAULT;
> +			if (kvm_slot_dirty_track_enabled(slot))
>   				goto out;
> -			}
>   		}
>   
>   		/* Track dirtying of writeable pages */
> @@ -615,10 +608,10 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
>   		if (page)
>   			put_page(page);
>   	}
> -	return ret;
> +	return 0;
>   out:
>   	spin_unlock(&kvm->mmu_lock);
> -	return ret;
> +	return -EFAULT;
>   }
>   
>   static bool fault_supports_huge_mapping(struct kvm_memory_slot *memslot,
>