From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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: Tony Krowiak Date: Tue, 16 Apr 2019 09:11:19 -0400 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Language: en-US Content-Transfer-Encoding: 8bit Message-Id: <8ee6f624-b698-bf83-2ae0-e292ad2512fc@linux.ibm.com> Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: pmorel@linux.ibm.com, 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 4/16/19 3:52 AM, Pierre Morel wrote: > 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. Based on comments by Connie, I plan on removing this patch from the next version. > > >> + >> +    /* 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; >> +} >> + >