linux-kernel - Re: [PATCH V5 5/5] KVM: Small Refactoring to kvm_free

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Message-ID: <20181029165109.GB27144@linux.intel.com>
Date:   Mon, 29 Oct 2018 09:51:09 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Ahmed Abd El Mawgood <ahmedsoliman0x666@...il.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, rkrcmar@...hat.com,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        hpa@...or.com, x86@...nel.org, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        ovich00@...il.com, kernel-hardening@...ts.openwall.com,
        nigel.edwards@....com, Boris Lukashev <blukashev@...pervictus.com>,
        Hossam Hassan <7ossam9063@...il.com>,
        Ahmed Lotfy <A7med.lotfey@...il.com>
Subject: Re: [PATCH V5 5/5] KVM: Small Refactoring to kvm_free_memslot

On Fri, Oct 26, 2018 at 05:12:23PM +0200, Ahmed Abd El Mawgood wrote:
> This should be a little bit more readable and prone to memory leaks

Describe what is being, both in the subject line and continuing on in
the full changelog, e.g. "Small Refactoring to kvm_free_memslot" doesn't
provide any clue as to what is being done.  And this is not what I would
describe as refactoring, e.g. verifying the new behavior means tracing
through its impact on __kvm_set_memory_region().

Lastly, this should be sent as a separate patch.  There is no dependency
on the ROE code and if it actually addresses a potential memory leak (I
haven't actually reviewed the code itself) it should go in sooner rather
than later.

> 
> Signed-off-by: Ahmed Abd El Mawgood <ahmedsoliman0x666@...il.com>
> ---
>  virt/kvm/kvm_main.c | 15 +++++++--------
>  1 file changed, 7 insertions(+), 8 deletions(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 2d3011e8490e..79c98db03c84 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -550,11 +550,11 @@ static void kvm_destroy_dirty_bitmap(struct kvm_memory_slot *memslot)
>   * Free any memory in @free but not in @dont.
>   */
>  static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
> -			      struct kvm_memory_slot *dont)
> +			      struct kvm_memory_slot *dont,
> +			      enum kvm_mr_change change)
>  {
> +	if (change == KVM_MR_DELETE) {
>  #ifdef CONFIG_KVM_ROE
> -	if (!dont) {
> -		//TODO still this might leak
>  		struct protected_chunk *pos, *n;
>  		struct list_head *head = free->prot_list;
>  		kvfree(free->roe_bitmap);
> @@ -564,10 +564,9 @@ static void kvm_free_memslot(struct kvm *kvm, struct kvm_memory_slot *free,
>  			kvfree(pos);
>  		}
>  		kvfree(free->prot_list);
> -	}
>  #endif
> -	if (!dont || free->dirty_bitmap != dont->dirty_bitmap)
>  		kvm_destroy_dirty_bitmap(free);
> +	}
>  
>  	kvm_arch_free_memslot(kvm, free, dont);
>  
> @@ -582,7 +581,7 @@ static void kvm_free_memslots(struct kvm *kvm, struct kvm_memslots *slots)
>  		return;
>  
>  	kvm_for_each_memslot(memslot, slots)
> -		kvm_free_memslot(kvm, memslot, NULL);
> +		kvm_free_memslot(kvm, memslot, NULL, KVM_MR_DELETE);
>  
>  	kvfree(slots);
>  }
> @@ -1100,14 +1099,14 @@ int __kvm_set_memory_region(struct kvm *kvm,
>  
>  	kvm_arch_commit_memory_region(kvm, mem, &old, &new, change);
>  
> -	kvm_free_memslot(kvm, &old, &new);
> +	kvm_free_memslot(kvm, &old, &new, change);
>  	kvfree(old_memslots);
>  	return 0;
>  
>  out_slots:
>  	kvfree(slots);
>  out_free:
> -	kvm_free_memslot(kvm, &new, &old);
> +	kvm_free_memslot(kvm, &new, &old, change);
>  out:
>  	return r;
>  }
> -- 
> 2.18.1
>