linux-kernel - Re: [RFC PATCH 5/9] kvm_main.c: split __kvm_set_memory_region logic in kvm_check_mem and kvm_prepare

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Date:   Tue, 13 Sep 2022 10:56:13 +0800
From:   "Yang, Weijiang" <weijiang.yang@...el.com>
To:     Emanuele Giuseppe Esposito <eesposit@...hat.com>
CC:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        "Maxim Levitsky" <mlevitsk@...hat.com>, <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>, <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [RFC PATCH 5/9] kvm_main.c: split __kvm_set_memory_region logic
 in kvm_check_mem and kvm_prepare_batch


On 9/9/2022 6:45 PM, Emanuele Giuseppe Esposito wrote:
> Just a function split. No functional change intended,
> except for the fact that kvm_prepare_batch() does not
> immediately call kvm_set_memslot() if batch->change is
> KVM_MR_DELETE, but delegates the caller (__kvm_set_memory_region).
>
>
> +static int kvm_check_memory_region(struct kvm *kvm,
> +				const struct kvm_userspace_memory_region *mem,
> +				struct kvm_internal_memory_region_list *batch)
> +{
> +	int r;
> +
> +	r = check_memory_region_flags(mem);
> +	if (r)
> +		return r;
>   
> -	r = kvm_set_memslot(kvm, batch);
> +	r = kvm_check_mem(mem);
>   	if (r)
> -		kfree(new);
> +		return r;
> +
> +	r = kvm_prepare_batch(kvm, mem, batch);
> +	if (r && batch->new)
> +		kfree(batch->new);
 From the patch, r !=0 and batch->new !=NULL are exclusive, so free() 
here is not reachable.
> +
>   	return r;
>   }
[...]
>