Re: [PATCH v8 09/22] s390: vfio-ap: register matrix device with VFIO mdev framework

[Pierre Morel]

On 09/08/2018 13:06, Cornelia Huck wrote:
> On Wed,  8 Aug 2018 10:44:19 -0400
> Tony Krowiak <akrowiak@xxxxxxxxxxxxxxxxxx> wrote:
>
> > diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> > index d7e39ad..6a827f3 100644
> > --- a/drivers/s390/crypto/vfio_ap_drv.c
> > +++ b/drivers/s390/crypto/vfio_ap_drv.c
> > @@ -12,6 +12,7 @@
> >   #include <linux/mod_devicetable.h>
> >   #include <linux/slab.h>
> >   #include <linux/string.h>
> > +#include <asm/zcrypt.h>
> >   #include "vfio_ap_private.h"
> >   
> >   #define VFIO_AP_ROOT_NAME "vfio_ap"
> > @@ -68,6 +69,18 @@ static int vfio_ap_matrix_dev_create(void)
> >   {
> >   	int ret;
> >   
> > +	mutex_init(&matrix_dev.lock);
> > +	INIT_LIST_HEAD(&matrix_dev.mdev_list);
> > +
> > +	/* Test if PQAP(QCI) instruction is available */
> > +	if (test_facility(12)) {
> > +		ret = ap_qci(&matrix_dev.info);
> > +		if (ret)
> > +			return ret;
> > +	}
> > +
> > +	atomic_set(&matrix_dev.available_instances, MAX_ZDEV_ENTRIES_EXT);
> > +
> >   	ret = misc_register(&matrix_dev.misc_dev);
> OK, you are adding more stuff other than the miscdevice after all...
> still, I don't think that this is a good idea.
>
> I think I had already asked this for a previous version: Why has this
> been turned into a miscdevice? (I think my reaction to the answer was
> 'meh'... but I think more and more that we should not do that.)

Following our off-line conversation...

I understand your concern, about the misc device and dynamically
updating the misc device structure.

For it is your main point of contention and we do not currently have
a use case for the misc device I propose we just let it go and
rebase on the device design we had in V6 and did not seem to
make any trouble to any one.

We will propose a v9 with the integration of all comment done
so far soon as possible.


Best regards,

Pierre


> >   	if (ret)
> >   		return ret;


--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany