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

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Date:   Fri, 10 Aug 2018 10:59:33 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Pierre Morel <pmorel@...ux.ibm.com>
Cc:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        kwankhede@...dia.com, bjsdjshi@...ux.vnet.ibm.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pmorel@...ux.vnet.ibm.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com,
        frankja@...ux.ibm.com, Tony Krowiak <akrowiak@...ux.ibm.com>
Subject: Re: [PATCH v8 09/22] s390: vfio-ap: register matrix device with
 VFIO mdev framework

On Thu, 9 Aug 2018 18:27:16 +0200
Pierre Morel <pmorel@...ux.ibm.com> wrote:

> On 09/08/2018 13:06, Cornelia Huck wrote:
> > On Wed,  8 Aug 2018 10:44:19 -0400
> > Tony Krowiak <akrowiak@...ux.vnet.ibm.com> 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.

Sounds good to me!