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

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Date:   Thu, 9 Aug 2018 13:06:07 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
Cc:     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 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.)

>  	if (ret)
>  		return ret;