linux-kernel - Re: [PATCH v3 07/15] KVM: Refactor error handling for setting memory region

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Message-ID: <3b6cd050-2551-d262-aded-051e25044519@amsat.org>
Date:   Thu, 5 Dec 2019 10:49:50 +0100
From:   Philippe Mathieu-Daudé <f4bug@...at.org>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        James Hogan <jhogan@...nel.org>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Marc Zyngier <maz@...nel.org>
Cc:     David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-mips@...r.kernel.org, kvm-ppc@...r.kernel.org,
        kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        Christoffer Dall <christoffer.dall@....com>
Subject: Re: [PATCH v3 07/15] KVM: Refactor error handling for setting memory
 region

On 10/25/19 1:07 AM, Sean Christopherson wrote:
> Replace a big pile o' gotos with returns to make it more obvious what
> error code is being returned, and to prepare for refactoring the
> functional, i.e. post-checks, portion of __kvm_set_memory_region().
> 
> Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>   virt/kvm/kvm_main.c | 40 ++++++++++++++++++----------------------
>   1 file changed, 18 insertions(+), 22 deletions(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index a43902d9036d..e2f47d60f696 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -942,34 +942,33 @@ int __kvm_set_memory_region(struct kvm *kvm,
>   
>   	r = check_memory_region_flags(mem);
>   	if (r)
> -		goto out;
> +		return r;
>   
> -	r = -EINVAL;
>   	as_id = mem->slot >> 16;
>   	id = (u16)mem->slot;
>   
>   	/* General sanity checks */
>   	if (mem->memory_size & (PAGE_SIZE - 1))
> -		goto out;
> +		return -EINVAL;
>   	if (mem->guest_phys_addr & (PAGE_SIZE - 1))
> -		goto out;
> +		return -EINVAL;
>   	/* We can read the guest memory with __xxx_user() later on. */
>   	if ((id < KVM_USER_MEM_SLOTS) &&
>   	    ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
>   	     !access_ok((void __user *)(unsigned long)mem->userspace_addr,
>   			mem->memory_size)))
> -		goto out;
> +		return -EINVAL;
>   	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_MEM_SLOTS_NUM)
> -		goto out;
> +		return -EINVAL;
>   	if (mem->guest_phys_addr + mem->memory_size < mem->guest_phys_addr)
> -		goto out;
> +		return -EINVAL;
>   
>   	slot = id_to_memslot(__kvm_memslots(kvm, as_id), id);
>   	base_gfn = mem->guest_phys_addr >> PAGE_SHIFT;
>   	npages = mem->memory_size >> PAGE_SHIFT;
>   
>   	if (npages > KVM_MEM_MAX_NR_PAGES)
> -		goto out;
> +		return -EINVAL;
>   
>   	new = old = *slot;
>   
> @@ -986,20 +985,18 @@ int __kvm_set_memory_region(struct kvm *kvm,
>   			if ((new.userspace_addr != old.userspace_addr) ||
>   			    (npages != old.npages) ||
>   			    ((new.flags ^ old.flags) & KVM_MEM_READONLY))
> -				goto out;
> +				return -EINVAL;
>   
>   			if (base_gfn != old.base_gfn)
>   				change = KVM_MR_MOVE;
>   			else if (new.flags != old.flags)
>   				change = KVM_MR_FLAGS_ONLY;
> -			else { /* Nothing to change. */
> -				r = 0;
> -				goto out;
> -			}
> +			else /* Nothing to change. */
> +				return 0;
>   		}
>   	} else {
>   		if (!old.npages)
> -			goto out;
> +			return -EINVAL;
>   
>   		change = KVM_MR_DELETE;
>   		new.base_gfn = 0;
> @@ -1008,29 +1005,29 @@ int __kvm_set_memory_region(struct kvm *kvm,
>   
>   	if ((change == KVM_MR_CREATE) || (change == KVM_MR_MOVE)) {
>   		/* Check for overlaps */
> -		r = -EEXIST;
>   		kvm_for_each_memslot(slot, __kvm_memslots(kvm, as_id)) {
>   			if (slot->id == id)
>   				continue;
>   			if (!((base_gfn + npages <= slot->base_gfn) ||
>   			      (base_gfn >= slot->base_gfn + slot->npages)))
> -				goto out;
> +				return -EEXIST;
>   		}
>   	}
>   
> -	r = -ENOMEM;
> -
>   	/* Allocate/free page dirty bitmap as needed */
>   	if (!(new.flags & KVM_MEM_LOG_DIRTY_PAGES))
>   		new.dirty_bitmap = NULL;
>   	else if (!new.dirty_bitmap) {
> -		if (kvm_create_dirty_bitmap(&new) < 0)
> -			goto out;
> +		r = kvm_create_dirty_bitmap(&new);
> +		if (r)
> +			return r;

Reviewed-by: Philippe Mathieu-Daudé <f4bug@...at.org>

>   	}
>   
>   	slots = kvzalloc(sizeof(struct kvm_memslots), GFP_KERNEL_ACCOUNT);
> -	if (!slots)
> +	if (!slots) {
> +		r = -ENOMEM;
>   		goto out_bitmap;
> +	}
>   	memcpy(slots, __kvm_memslots(kvm, as_id), sizeof(struct kvm_memslots));
>   
>   	if ((change == KVM_MR_DELETE) || (change == KVM_MR_MOVE)) {
> @@ -1081,7 +1078,6 @@ int __kvm_set_memory_region(struct kvm *kvm,
>   out_bitmap:
>   	if (new.dirty_bitmap && !old.dirty_bitmap)
>   		kvm_destroy_dirty_bitmap(&new);
> -out:
>   	return r;
>   }
>   EXPORT_SYMBOL_GPL(__kvm_set_memory_region);
>