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SubjectRe: [PATCH 6/7] KVM: arm64: Change return type of kvm_vm_ioctl_mte_copy_tags() to "int"
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Hi Thomas,

On 2/3/23 8:42 PM, Thomas Huth wrote:
> This function only returns normal integer values, so there is
> no need to declare its return value as "long".
>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
> arch/arm64/include/asm/kvm_host.h | 4 ++--
> arch/arm64/kvm/guest.c | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 35a159d131b5..b1a16343767f 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -963,8 +963,8 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,
> int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
> struct kvm_device_attr *attr);
>
> -long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> - struct kvm_arm_copy_mte_tags *copy_tags);
> +int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> + struct kvm_arm_copy_mte_tags *copy_tags);
>
> /* Guest/host FPSIMD coordination helpers */
> int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index cf4c495a4321..80e530549c34 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -1013,8 +1013,8 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
> return ret;
> }
>
> -long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> - struct kvm_arm_copy_mte_tags *copy_tags)
> +int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> + struct kvm_arm_copy_mte_tags *copy_tags)
> {
> gpa_t guest_ipa = copy_tags->guest_ipa;
> size_t length = copy_tags->length;
>

It's possible for the function to return number of bytes have been copied.
Its type is 'size_t', same to 'unsigned long'. So 'int' doesn't have sufficient
space for it if I'm correct.

long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
struct kvm_arm_copy_mte_tags *copy_tags)
{
gpa_t guest_ipa = copy_tags->guest_ipa;
size_t length = copy_tags->length;
:
:
out:
mutex_unlock(&kvm->slots_lock);
/* If some data has been copied report the number of bytes copied */
if (length != copy_tags->length)
return copy_tags->length - length;
return ret;
}

Thanks,
Gavin

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