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> <8ee6f624-b698-bf83-2ae0-e292ad2512fc@linux.ibm.com> From: Pierre Morel Date: Tue, 16 Apr 2019 15:13:58 +0200 MIME-Version: 1.0 In-Reply-To: <8ee6f624-b698-bf83-2ae0-e292ad2512fc@linux.ibm.com> Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Language: en-US Content-Transfer-Encoding: 8bit Message-Id: <46d627f1-9414-8636-6975-793bbe11b616@linux.ibm.com> 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 16/04/2019 15:11, Tony Krowiak wrote: > 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. Yes it was the goal. > >> >> >>> + >>> +    /* 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