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SubjectRe: [PATCH] s390/vfio-ap: do not use open locks during VFIO_GROUP_NOTIFY_SET_KVM notification
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On 6/28/21 2:22 PM, Jason Gunthorpe wrote:
> On Mon, Jun 28, 2021 at 02:20:55PM -0400, Tony Krowiak wrote:
>>
>> On 6/28/21 1:34 PM, Jason Gunthorpe wrote:
>>> On Fri, Jun 25, 2021 at 06:07:58PM -0400, Tony Krowiak wrote:
>>>> static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
>>>> {
>>>> + mutex_lock(&matrix_dev->lock);
>>>> + if ((matrix_mdev->kvm) && (matrix_mdev->kvm->arch.crypto.crycbd)) {
>>>> mutex_unlock(&matrix_dev->lock);
>>>> + down_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem);
>>>> + matrix_mdev->kvm->arch.crypto.pqap_hook = NULL;
>>>> + up_write(&matrix_mdev->kvm->arch.crypto.pqap_hook_rwsem);
>>>> + kvm_arch_crypto_clear_masks(matrix_mdev->kvm);
>>>> mutex_lock(&matrix_dev->lock);
>>>> vfio_ap_mdev_reset_queues(matrix_mdev->mdev);
>>>> kvm_put_kvm(matrix_mdev->kvm);
>>>> matrix_mdev->kvm = NULL;
>>>> + mutex_unlock(&matrix_dev->lock);
>>>> }
>>> Doesn't a flow exit the function with matrix_dev->lock held he

Yes, you are correct. Stupid mistake.

>> How can that happen? What flow?
> When the if isn't taken
>
>>> Write it with 'success oriented flow'
>> I'm not sure what you mean, can you clarify this statement?
> Basically, don't write the bulk of the function under an if statement
>
> mutex_lock(&matrix_dev->lock);
> if (!matrix_mdev->kvm || !matrix_mdev->kvm->arch.crypto.crycbd) {
> mutex_unlock(&matrix_dev->lock);
> return;
> }

Sure.

>
> Jason
>

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