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Subject: Re: [PATCH v2] KVM: const-ify all relevant uses of struct
 kvm_memory_slot
To:     Hamza Mahfooz <someguy@effective-light.com>,
        linux-kernel@vger.kernel.org
Cc:     Peter Xu <peterx@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
        kvm@vger.kernel.org
References: <20210730222704.61672-1-someguy@effective-light.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <fcab24b9-0573-9165-20e9-683586e86bdf@redhat.com>
Date:   Mon, 2 Aug 2021 15:40:08 +0200
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On 31/07/21 00:27, Hamza Mahfooz wrote:
> @@ -1440,7 +1440,7 @@ static bool kvm_set_pte_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
>   
>   struct slot_rmap_walk_iterator {
>   	/* input fields. */
> -	struct kvm_memory_slot *slot;
> +	const struct kvm_memory_slot *slot;
>   	gfn_t start_gfn;
>   	gfn_t end_gfn;
>   	int start_level;
> @@ -1467,16 +1467,20 @@ rmap_walk_init_level(struct slot_rmap_walk_iterator *iterator, int level)
>   
>   static void
>   slot_rmap_walk_init(struct slot_rmap_walk_iterator *iterator,
> -		    struct kvm_memory_slot *slot, int start_level,
> +		    const struct kvm_memory_slot *slot, int start_level,
>   		    int end_level, gfn_t start_gfn, gfn_t end_gfn)
>   {
> -	iterator->slot = slot;
> -	iterator->start_level = start_level;
> -	iterator->end_level = end_level;
> -	iterator->start_gfn = start_gfn;
> -	iterator->end_gfn = end_gfn;
> +	struct slot_rmap_walk_iterator iter = {
> +		.slot = slot,
> +		.start_gfn = start_gfn,
> +		.end_gfn = end_gfn,
> +		.start_level = start_level,
> +		.end_level = end_level
> +	};
> +
> +	rmap_walk_init_level(&iter, start_level);
>   
> -	rmap_walk_init_level(iterator, iterator->start_level);
> +	memcpy(iterator, &iter, sizeof(struct slot_rmap_walk_iterator));
>   }
>   
>   static bool slot_rmap_walk_okay(struct slot_rmap_walk_iterator *iterator)

I don't understand, just changing the argument works.  There is no need 
to change the body of the function.

Paolo