From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [PATCH v8 17/22] s390: vfio-ap: zeroize the AP queues. Date: Fri, 10 Aug 2018 13:16:48 +0200 Message-ID: <20180810131648.4fab1d7a.cohuck@redhat.com> References: <1533739472-7172-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1533739472-7172-18-git-send-email-akrowiak@linux.vnet.ibm.com> <20180810111445.015fcf2a.cohuck@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, borntraeger@de.ibm.com, kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com, alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com, alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com, thuth@redhat.com, pasic@linux.vnet.ibm.com, berrange@redhat.com, fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com, frankja@linux.ibm.com, Tony Krowiak To: Pierre Morel Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, 10 Aug 2018 12:49:08 +0200 Pierre Morel wrote: > On 10/08/2018 11:14, Cornelia Huck wrote: > > On Wed, 8 Aug 2018 10:44:27 -0400 > > Tony Krowiak wrote: > > > >> From: Tony Krowiak > >> > >> Let's call PAPQ(ZAPQ) to zeroize a queue: > >> > >> * For each queue configured for a mediated matrix device > >> when it is released. > >> > >> Zeroizing a queue resets the queue, clears all pending > >> messages for the queue entries and disables adapter interruptions > >> associated with the queue. > >> > >> Signed-off-by: Tony Krowiak > >> Reviewed-by: Halil Pasic > >> Tested-by: Michael Mueller > >> Tested-by: Farhan Ali > >> Signed-off-by: Christian Borntraeger > >> --- > >> drivers/s390/crypto/vfio_ap_ops.c | 29 ++++++++++++++++++++++++++++- > >> drivers/s390/crypto/vfio_ap_private.h | 25 +++++++++++++++++++++++++ > >> 2 files changed, 53 insertions(+), 1 deletions(-) > >> > >> @@ -788,7 +812,10 @@ static void vfio_ap_mdev_release(struct mdev_device *mdev) > >> { > >> struct ap_matrix_mdev *matrix_mdev = mdev_get_drvdata(mdev); > >> > >> - kvm_arch_crypto_clear_masks(matrix_mdev->kvm); > >> + if (matrix_mdev->kvm) > >> + kvm_arch_crypto_clear_masks(matrix_mdev->kvm); > > Confused. Why is the check for matrix_mdev->kvm added here? > > When using the KVM notifier we can get two notifications: > -> KVM is here / is comming > -> KVM is not here / disappearing > > In the first case we initialize matrix_mdev->kvm with a pointer to KVM > In the second case we nullify the pointer. > > During the open of the mediated device, the guest should have been started > or we refuse to start. > > During the close of the mediated device, the guest should be there, but > we have no certitude that the guest did not disappear before the VFIO > file being closed. > Since we do not allow multiple guests using the same mediated device > this case should not happen with QEMU. But I am not sure that > a rogue user program could not stop KVM before closing the VFIO > mediated device. I'm not sure why the check is introduced in this patch, though. But maybe I just need weekend :) > > Maybe Alex can confirm this point, if not we can remove the test.