Messages in this thread | | | Subject | Re: [PATCH v10 04/16] s390/zcrypt: driver callback to indicate resource in use | From | Tony Krowiak <> | Date | Thu, 17 Sep 2020 09:54:07 -0400 |
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On 9/17/20 8:14 AM, Cornelia Huck wrote: > On Tue, 15 Sep 2020 15:32:35 -0400 > Tony Krowiak <akrowiak@linux.ibm.com> wrote: > >> On 9/14/20 11:29 AM, Cornelia Huck wrote: >>> On Fri, 21 Aug 2020 15:56:04 -0400 >>> Tony Krowiak <akrowiak@linux.ibm.com> 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. The intent of >>>> this callback is to provide a driver with the means to prevent a root user >>>> from inadvertently taking a queue away from a matrix mdev and giving it to >>>> the host while it is assigned to the matrix mdev. The callback will >>>> be invoked whenever a change to the AP bus's sysfs apmask or aqmask >>>> attributes would 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 facilitates pass-through of an AP queue to a >>>> guest. The idea here is that a guest may be administered by a different >>>> sysadmin than the host and we don't want AP resources to unexpectedly >>>> disappear from a guest's AP configuration (i.e., adapters, domains and >>>> control domains assigned to the matrix mdev). This will enforce the proper >>>> procedure for removing AP resources intended for guest usage which is to >>>> first unassign them from the matrix mdev, then unbind them from the >>>> vfio_ap device driver. >>>> >>>> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> >>>> Reported-by: kernel test robot <lkp@intel.com> >>> This looks a bit odd... >> I've removed all of those. These kernel test robot errors were flagged >> in the last series. The review comments from the robot suggested >> the reported-by, but I assume that was for patches intended to >> fix those errors, so I am removing these as per Christian's comments. > Yes, I think the Reported-by: mostly makes sense if you include a patch > to fix something on top. > >>> >>>> --- >>>> drivers/s390/crypto/ap_bus.c | 148 ++++++++++++++++++++++++++++++++--- >>>> drivers/s390/crypto/ap_bus.h | 4 + >>>> 2 files changed, 142 insertions(+), 10 deletions(-) >>>> >>> (...) >>> >>>> @@ -1107,12 +1118,70 @@ 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; >>>> + >>>> + /* >>>> + * No need to verify whether the driver is using the queues if it is the >>>> + * default driver. >>>> + */ >>>> + if (ap_drv->flags & AP_DRIVER_FLAG_DEFAULT) >>>> + return 0; >>>> + >>>> + /* The non-default driver's module must be loaded */ >>>> + if (!try_module_get(drv->owner)) >>>> + return 0; >>>> + >>>> + if (ap_drv->in_use) >>>> + if (ap_drv->in_use(newapm, ap_perms.aqm)) >>>> + rc = -EADDRINUSE; >>> ISTR that Christian suggested -EBUSY in a past revision of this series? >>> I think that would be more appropriate. >> I went back and looked and sure enough, he did recommend that. >> You have a great memory! I didn't respond to that comment, so I >> must have missed it at the time. >> >> I personally prefer EADDRINUSE because I think it is more indicative >> of the reason an AP resource can not be assigned back to the host >> drivers is because it is in use by a guest or, at the very least, reserved >> for use by a guest (i.e., assigned to an mdev). To say it is busy implies >> that the device is busy performing encryption services which may or >> may not be true at a given moment. Even if so, that is not the reason >> for refusing to allow reassignment of the device. > I have a different understanding of these error codes: EADDRINUSE is > something used in the networking context when an actual address is > already used elsewhere. EBUSY is more of a generic error that indicates > that a certain resource is not free to perform the requested operation; > it does not necessarily mean that the resource is currently actively > doing something. Kind of when you get EBUSY when trying to eject > something another program holds a reference on: that other program > might not actually be doing anything, but it potentially could.
I'll go ahead and change it to -EBUSY.
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