From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Reply-To: pmorel@linux.ibm.com Subject: Re: [PATCH 1/7] s390: zcrypt: driver callback to indicate resource in use References: <1555016604-2008-1-git-send-email-akrowiak@linux.ibm.com> <1555016604-2008-2-git-send-email-akrowiak@linux.ibm.com> From: Pierre Morel Date: Tue, 16 Apr 2019 09:52:26 +0200 MIME-Version: 1.0 In-Reply-To: <1555016604-2008-2-git-send-email-akrowiak@linux.ibm.com> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Language: en-US Content-Transfer-Encoding: 8bit Message-Id: Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: freude@linux.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.com, frankja@linux.ibm.com, david@redhat.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, pasic@linux.ibm.com, alex.williamson@redhat.com, kwankhede@nvidia.com List-ID: On 11/04/2019 23:03, Tony Krowiak wrote: > Introduces a new driver callback to prevent a root user from unbinding > an AP queue from its device driver if the queue is in use. This prevents > a root user from inadvertently taking a queue away from a guest and > giving it to the host, or vice versa. The callback will be invoked > whenever a change to the AP bus's apmask or aqmask sysfs interfaces may > result in one or more AP queues being removed from its driver. If the > callback responds in the affirmative for any driver queried, the change > to the apmask or aqmask will be rejected with a device in use error. > > For this patch, only non-default drivers will be queried. Currently, > there is only one non-default driver, the vfio_ap device driver. The > vfio_ap device driver manages AP queues passed through to one or more > guests and we don't want to unexpectedly take AP resources away from > guests which are most likely independently administered. > > Signed-off-by: Tony Krowiak > --- > drivers/s390/crypto/ap_bus.c | 138 +++++++++++++++++++++++++++++++++++++++++-- > drivers/s390/crypto/ap_bus.h | 3 + > 2 files changed, 135 insertions(+), 6 deletions(-) > > diff --git a/drivers/s390/crypto/ap_bus.c b/drivers/s390/crypto/ap_bus.c > index 1546389d71db..66a5a9d9fae6 100644 > --- a/drivers/s390/crypto/ap_bus.c > +++ b/drivers/s390/crypto/ap_bus.c > @@ -35,6 +35,7 @@ > #include > #include > #include > +#include > > #include "ap_bus.h" > #include "ap_debug.h" > @@ -980,9 +981,11 @@ int ap_parse_mask_str(const char *str, > newmap = kmalloc(size, GFP_KERNEL); > if (!newmap) > return -ENOMEM; > - if (mutex_lock_interruptible(lock)) { > - kfree(newmap); > - return -ERESTARTSYS; > + if (lock) { > + if (mutex_lock_interruptible(lock)) { > + kfree(newmap); > + return -ERESTARTSYS; > + } > } > > if (*str == '+' || *str == '-') { > @@ -994,7 +997,10 @@ int ap_parse_mask_str(const char *str, > } > if (rc == 0) > memcpy(bitmap, newmap, size); > - mutex_unlock(lock); > + > + if (lock) > + mutex_unlock(lock); > + > kfree(newmap); > return rc; > } > @@ -1181,12 +1187,72 @@ static ssize_t apmask_show(struct bus_type *bus, char *buf) > return rc; > } > > +static int __verify_card_reservations(struct device_driver *drv, void *data) > +{ > + int rc = 0; > + struct ap_driver *ap_drv = to_ap_drv(drv); > + unsigned long *newapm = (unsigned long *)data; > + > + /* > + * If the reserved bits do not identify cards reserved for use by the > + * non-default driver, there is no need to verify the driver is using > + * the queues. > + */ > + if (ap_drv->flags & AP_DRIVER_FLAG_DEFAULT) > + return 0; I prefer you suppress this asymmetry with the assumption that the "default driver" will not register a "in_use" callback. > + > + /* Pin the driver's module code */ > + if (!try_module_get(drv->owner)) > + return 0; > + > + if (ap_drv->in_use) > + if (ap_drv->in_use(newapm, ap_perms.aqm)) > + rc = -EADDRINUSE; > + > + module_put(drv->owner); > + > + return rc; > +} > + -- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany