From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Krowiak Subject: Re: [PATCH v6 3/7] s390: ap: setup relation betwen KVM and mediated device Date: Fri, 29 Mar 2019 09:06:00 -0400 Message-ID: References: <1553265828-27823-1-git-send-email-pmorel@linux.ibm.com> <1553265828-27823-4-git-send-email-pmorel@linux.ibm.com> <1ea236d1-ca0b-03c0-3699-0c0deb435785@linux.ibm.com> <3cd496d0-3eec-78e8-9ea5-4d62fe0cff1c@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: pmorel@linux.ibm.com, borntraeger@de.ibm.com Cc: alex.williamson@redhat.com, cohuck@redhat.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org, frankja@linux.ibm.com, pasic@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, freude@linux.ibm.com, mimu@linux.ibm.com List-ID: On 3/29/19 4:58 AM, Pierre Morel wrote: > On 28/03/2019 18:25, Tony Krowiak wrote: >> On 3/28/19 12:27 PM, Pierre Morel wrote: >>> On 28/03/2019 17:12, Tony Krowiak wrote: >>>> On 3/22/19 10:43 AM, Pierre Morel wrote: >>>>> When the mediated device is open we setup the relation with KVM >>>>> unset it >>>>> when the mediated device is released. >>>> >>>> s/open we setup/open, we set up/ >>>> s/with KVM unset/with KVM and unset/ >>>> >>>>> >>>>> We lock the matrix mediated device to avoid any change until the >>>>> open is done. >>>>> We make sure that KVM is present when opening the mediated device >>>>> otherwise we return an error. >>>> >>>> s/mediated device/mediated device,/ >>>> >>>>> >>>>> Increase kvm's refcount to ensure the KVM structures are still >>>>> available >>>>> during the use of the mediated device by the guest. >>>>> >>>>> Signed-off-by: Pierre Morel >>>>> --- >>>>>   drivers/s390/crypto/vfio_ap_ops.c | 143 >>>>> +++++++++++++++++++++----------------- >>>>>   1 file changed, 79 insertions(+), 64 deletions(-) >>>>> >>>>> diff --git a/drivers/s390/crypto/vfio_ap_ops.c >>>>> b/drivers/s390/crypto/vfio_ap_ops.c >>>>> index 77f7bac..bdb36e0 100644 >>>>> --- a/drivers/s390/crypto/vfio_ap_ops.c >>>>> +++ b/drivers/s390/crypto/vfio_ap_ops.c >>>>> @@ -787,74 +787,24 @@ static const struct attribute_group >>>>> *vfio_ap_mdev_attr_groups[] = { >>>>>       NULL >>>>>   }; >>>>> -/** >>>>> - * vfio_ap_mdev_set_kvm >>>>> - * >>>>> - * @matrix_mdev: a mediated matrix device >>>>> - * @kvm: reference to KVM instance >>>>> - * >>>>> - * Verifies no other mediated matrix device has @kvm and sets a >>>>> reference to >>>>> - * it in @matrix_mdev->kvm. >>>>> - * >>>>> - * Return 0 if no other mediated matrix device has a reference to >>>>> @kvm; >>>>> - * otherwise, returns an -EPERM. >>>>> - */ >>>>> -static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev, >>>>> -                struct kvm *kvm) >>>>> -{ >>>>> -    struct ap_matrix_mdev *m; >>>>> - >>>>> -    mutex_lock(&matrix_dev->lock); >>>>> - >>>>> -    list_for_each_entry(m, &matrix_dev->mdev_list, node) { >>>>> -        if ((m != matrix_mdev) && (m->kvm == kvm)) { >>>>> -            mutex_unlock(&matrix_dev->lock); >>>>> -            return -EPERM; >>>>> -        } >>>>> -    } >>>>> - >>>>> -    matrix_mdev->kvm = kvm; >>>>> -    mutex_unlock(&matrix_dev->lock); >>>>> - >>>>> -    return 0; >>>>> -} >>>>> - >>>>>   static int vfio_ap_mdev_group_notifier(struct notifier_block *nb, >>>>>                          unsigned long action, void *data) >>>>>   { >>>>> -    int ret; >>>>>       struct ap_matrix_mdev *matrix_mdev; >>>>>       if (action != VFIO_GROUP_NOTIFY_SET_KVM) >>>>>           return NOTIFY_OK; >>>>>       matrix_mdev = container_of(nb, struct ap_matrix_mdev, >>>>> group_notifier); >>>>> - >>>>> -    if (!data) { >>>>> -        matrix_mdev->kvm = NULL; >>>>> -        return NOTIFY_OK; >>>>> -    } >>>>> - >>>>> -    ret = vfio_ap_mdev_set_kvm(matrix_mdev, data); >>>>> -    if (ret) >>>>> -        return NOTIFY_DONE; >>>>> - >>>>> -    /* If there is no CRYCB pointer, then we can't copy the masks */ >>>>> -    if (!matrix_mdev->kvm->arch.crypto.crycbd) >>>>> -        return NOTIFY_DONE; >>>>> - >>>>> -    kvm_arch_crypto_set_masks(matrix_mdev->kvm, >>>>> matrix_mdev->matrix.apm, >>>>> -                  matrix_mdev->matrix.aqm, >>>>> -                  matrix_mdev->matrix.adm); >>>>> +    matrix_mdev->kvm = data; >>>>>       return NOTIFY_OK; >>>>>   } >>>>> -static int vfio_ap_mdev_reset_queues(struct mdev_device *mdev) >>>>> +static int vfio_ap_mdev_reset_queues(struct ap_matrix_mdev >>>>> *matrix_mdev) >>>>>   { >>>>>       int ret; >>>>>       int rc = 0; >>>>> -    struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev); >>>>>       struct vfio_ap_queue *q; >>>>>       list_for_each_entry(q, &matrix_mdev->qlist, list) { >>>>> @@ -871,41 +821,106 @@ static int vfio_ap_mdev_reset_queues(struct >>>>> mdev_device *mdev) >>>>>       return rc; >>>>>   } >>>>> +/** >>>>> + * vfio_ap_mdev_set_kvm >>>>> + * >>>>> + * @matrix_mdev: a mediated matrix device >>>>> + * >>>>> + * - Verifies that the hook is free and install the PQAP hook >>>>> + * - Copy the matrix masks inside the CRYCB >>>>> + * - Increment the KVM rerference count >>>>> + * >>>>> + * Return 0 if no other mediated matrix device has a reference to >>>>> @kvm; >>>>> + * otherwise, returns an -EPERM. >>>>> + */ >>>>> +static int vfio_ap_mdev_set_kvm(struct ap_matrix_mdev *matrix_mdev) >>>>> +{ >>>>> +    if (matrix_mdev->kvm->arch.crypto.pqap_hook) >>>>> +        return -EPERM; >>>> >>>> How would this happen; in other words, why are we checking this? >>> >>> I check this to verify that no other AP mediated device is already in >>> use by this VM. >> >> Maybe you should insert a comment to that effect. > > Please notice that there is already a comment on this in the description > of the function. True, but that comment merely states that the function verifies the hook is free, not the reason why that particular check is done. When I reviewed the code and saw this check, I wondered why it was necessary. The comment you have would not have helped in this regard, so maybe you need to update your comment. > > Regards, > Pierre > > >