Date:   Wed, 28 Feb 2018 11:43:37 -0500
From:   Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
To:     Pierre Morel <pmorel@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        cohuck@...hat.com, kwankhede@...dia.com,
        bjsdjshi@...ux.vnet.ibm.com, pbonzini@...hat.com,
        alex.williamson@...hat.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com
Subject: Re: [PATCH v2 05/15] s390: vfio-ap: base implementation of VFIO AP
 device driver

On 02/28/2018 10:33 AM, Pierre Morel wrote:
> On 27/02/2018 15:28, Tony Krowiak wrote:
>> Introduces a new AP device driver. This device driver
>> is built on the VFIO mediated device framework. The framework
>> provides sysfs interfaces that facilitate passthrough
>> access by guests to devices installed on the linux host.
>>
>> The VFIO AP device driver will serve two purposes:
>>
>> 1. Provide the interfaces to reserve AP devices for exclusive
>>     use by KVM guests. This is accomplished by unbinding the
>>     devices to be reserved for guest usage from the default AP
>>     device driver and binding them to the VFIO AP device driver.
>>
>> 2. Implements the functions, callbacks and sysfs attribute
>>     interfaces required to create one or more VFIO mediated
>>     devices each of which will be used to configure the AP
>>     matrix for a guest and serve as a file descriptor
>>     for facilitating communication between QEMU and the
>>     VFIO AP device driver.
>>
>> When the VFIO AP device driver is initialized:
>>
>> * It registers with the AP bus for control of type 10 (CEX4
>>    and newer) AP queue devices. The probe and remove callbacks
>>    will be provided to support the binding/unbinding of
>>    AP queue devices to/from the VFIO AP device driver.
>>
>> * Creates a /sys/devices/vfio-ap/matrix device to hold
>>    the APQNs of the AP devices bound to the VFIO
>>    AP device driver and serves as the parent of the
>>    mediated devices created for each guest.
>>
>> Signed-off-by: Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
>> ---
>>   MAINTAINERS                             |    2 +
>>   arch/s390/Kconfig                       |    8 ++
>>   arch/s390/configs/default_defconfig     |    3 +
>>   arch/s390/configs/gcov_defconfig        |    3 +
>>   arch/s390/configs/performance_defconfig |    3 +
>>   arch/s390/defconfig                     |    3 +
>>   drivers/s390/crypto/Makefile            |    4 +
>>   drivers/s390/crypto/vfio_ap_drv.c       |  134 
>> +++++++++++++++++++++++++++++++
>>   drivers/s390/crypto/vfio_ap_private.h   |   20 +++++
>>   include/uapi/linux/vfio.h               |    2 +
>>   10 files changed, 182 insertions(+), 0 deletions(-)
>>   create mode 100644 drivers/s390/crypto/vfio_ap_drv.c
>>   create mode 100644 drivers/s390/crypto/vfio_ap_private.h
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 4acf7c2..a2f232d 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -11884,6 +11884,8 @@ W: 
>> http://www.ibm.com/developerworks/linux/linux390/
>>   S:    Supported
>>   F:    arch/s390/include/asm/kvm/kvm-ap.h
>>   F:    arch/s390/kvm/kvm-ap.c
>> +F:    drivers/s390/crypto/vfio_ap_drv.c
>> +F:    drivers/s390/crypto/vfio_ap_private.h
>>
>>   S390 ZFCP DRIVER
>>   M:    Steffen Maier <maier@...ux.vnet.ibm.com>
>> diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
>> index cbe1d97..9f23caf 100644
>> --- a/arch/s390/Kconfig
>> +++ b/arch/s390/Kconfig
>> @@ -771,6 +771,14 @@ config VFIO_CCW
>>         To compile this driver as a module, choose M here: the
>>         module will be called vfio_ccw.
>>
>> +config VFIO_AP
>> +    def_tristate m
>> +    prompt "Support for virtual Adjunct Processor device interface"
>
> The VFIO AP devices are not virtual.
> What about
>     "VFIO support for AP devices"
Sounds good.
>
>> +    depends on ZCRYPT && VFIO_MDEV_DEVICE
>> +    help
>> +        driver grants access to Adjunct Processor (AP) devices
>> +        via the VFIO mediated device interface.
>> +
>>   endmenu
>>
>>   menu "Dump support"
>> diff --git a/arch/s390/configs/default_defconfig 
>> b/arch/s390/configs/default_defconfig
>> index 5af8458..40fa3f6 100644
>> --- a/arch/s390/configs/default_defconfig
>> +++ b/arch/s390/configs/default_defconfig
>
> Not sure that this file belongs to this patch
Neither am I, but at the time I inserted this here - well before August 
of last year - I was using vfio-ccw as a model.
If someone can verify this does not belong here, I'd be more than happy 
to remove it.
>
>
>> @@ -719,3 +719,6 @@ CONFIG_APPLDATA_BASE=y
>>   CONFIG_KVM=m
>>   CONFIG_KVM_S390_UCONTROL=y
>>   CONFIG_VHOST_NET=m
>> +VFIO_MDEV=m
>> +VFIO_MDEV_DEVICE=m
>> +CONFIG_VFIO_AP=m
>
> What is your goal when modifying this three files?
> Could you add a comment in the commit message?
As stated above, this was originally based on the vfio-ccw model and has 
been in the
patch series since its inception. I'd be happy to remove it if it is not 
necessary.
>
>
>
>> diff --git a/arch/s390/configs/gcov_defconfig 
>> b/arch/s390/configs/gcov_defconfig
>> index d52eafe..377d40f 100644
>> --- a/arch/s390/configs/gcov_defconfig
>> +++ b/arch/s390/configs/gcov_defconfig
>> @@ -659,3 +659,6 @@ CONFIG_APPLDATA_BASE=y
>>   CONFIG_KVM=m
>>   CONFIG_KVM_S390_UCONTROL=y
>>   CONFIG_VHOST_NET=m
>> +VFIO_MDEV=m
>> +VFIO_MDEV_DEVICE=m
>> +CONFIG_VFIO_AP=m
>> diff --git a/arch/s390/configs/performance_defconfig 
>> b/arch/s390/configs/performance_defconfig
>> index 20ed149..f0c52df 100644
>> --- a/arch/s390/configs/performance_defconfig
>> +++ b/arch/s390/configs/performance_defconfig
>> @@ -657,3 +657,6 @@ CONFIG_APPLDATA_BASE=y
>>   CONFIG_KVM=m
>>   CONFIG_KVM_S390_UCONTROL=y
>>   CONFIG_VHOST_NET=m
>> +VFIO_MDEV=m
>> +VFIO_MDEV_DEVICE=m
>> +CONFIG_VFIO_AP=m
>> diff --git a/arch/s390/defconfig b/arch/s390/defconfig
>> index 46a3178..0996eb7 100644
>> --- a/arch/s390/defconfig
>> +++ b/arch/s390/defconfig
>> @@ -239,3 +239,6 @@ CONFIG_CRC7=m
>>   # CONFIG_XZ_DEC_ARMTHUMB is not set
>>   # CONFIG_XZ_DEC_SPARC is not set
>>   CONFIG_CMM=m
>> +VFIO_MDEV=m
>> +VFIO_MDEV_DEVICE=m
>> +CONFIG_VFIO_AP=m
>> diff --git a/drivers/s390/crypto/Makefile b/drivers/s390/crypto/Makefile
>> index b59af54..48e466e 100644
>> --- a/drivers/s390/crypto/Makefile
>> +++ b/drivers/s390/crypto/Makefile
>> @@ -15,3 +15,7 @@ obj-$(CONFIG_ZCRYPT) += zcrypt_pcixcc.o 
>> zcrypt_cex2a.o zcrypt_cex4.o
>>   # pkey kernel module
>>   pkey-objs := pkey_api.o
>>   obj-$(CONFIG_PKEY) += pkey.o
>> +
>> +# adjunct processor matrix
>> +vfio_ap-objs := vfio_ap_drv.o
>> +obj-$(CONFIG_VFIO_AP) += vfio_ap.o
>> diff --git a/drivers/s390/crypto/vfio_ap_drv.c 
>> b/drivers/s390/crypto/vfio_ap_drv.c
>> new file mode 100644
>> index 0000000..8bb72af
>> --- /dev/null
>> +++ b/drivers/s390/crypto/vfio_ap_drv.c
>> @@ -0,0 +1,134 @@
>> +/*
>> + * VFIO based AP device driver
>> + *
>> + * Copyright IBM Corp. 2017
>> + *
>> + * Author(s): Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/mod_devicetable.h>
>> +#include <linux/slab.h>
>> +
>> +#include "ap_bus.h"
>
> Since you do it in a later patch, may be put this include of ap_bus.h 
> in ap_private.h now.
Okay
>
>
>> +#include "vfio_ap_private.h"
>> +
>> +#define VFIO_AP_ROOT_NAME "vfio_ap"
>> +#define VFIO_AP_DEV_TYPE_NAME "ap_matrix"
>> +#define VFIO_AP_DEV_NAME "matrix"
>> +
>> +MODULE_AUTHOR("IBM Corporation");
>> +MODULE_DESCRIPTION("VFIO AP device driver, Copyright IBM Corp. 2017");
>> +MODULE_LICENSE("GPL v2");
>> +
>> +static struct device *vfio_ap_root_device;
>> +
>> +static struct ap_driver vfio_ap_drv;
>> +
>> +static struct ap_matrix *ap_matrix;
>> +
>> +static struct device_type vfio_ap_dev_type = {
>> +    .name = VFIO_AP_DEV_TYPE_NAME,
>> +};
>> +
>> +/* Only type 10 adapters (CEX4 and later) are supported
>> + * by the AP matrix device driver
>> + */
>> +static struct ap_device_id ap_queue_ids[] = {
>> +    { .dev_type = AP_DEVICE_TYPE_CEX4,
>> +      .match_flags = AP_DEVICE_ID_MATCH_QUEUE_TYPE },
>> +    { .dev_type = AP_DEVICE_TYPE_CEX5,
>> +      .match_flags = AP_DEVICE_ID_MATCH_QUEUE_TYPE },
>> +    { .dev_type = AP_DEVICE_TYPE_CEX6,
>> +      .match_flags = AP_DEVICE_ID_MATCH_QUEUE_TYPE },
>> +    { /* end of sibling */ },
>> +};
>> +
>> +MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids);
>> +
>> +static int vfio_ap_queue_dev_probe(struct ap_device *apdev)
>> +{
>> +    return 0;
>> +}
>> +
>> +static void vfio_ap_matrix_dev_release(struct device *dev)
>> +{
>> +    struct ap_matrix *ap_matrix = dev_get_drvdata(dev);
>> +
>> +    kfree(ap_matrix);
>> +}
>> +
>> +static int vfio_ap_matrix_dev_create(void)
>> +{
>> +    int ret;
>> +
>> +    vfio_ap_root_device = root_device_register(VFIO_AP_ROOT_NAME);
>> +
>> +    ret = PTR_ERR_OR_ZERO(vfio_ap_root_device);
>
> IS_ERR() is enough, root_device_register() never return NULL.
I searched the kernel code to look at other places the 
root_device_register()
function is called to see how the return value is handled. I've seen all 
of the
following used:
if (IS_ERR())
     ret = PTR_ERR()
PTR_ERR()
PTR_ERR_OR_ZERO()

I'm not sure why this is a concern, but I'll use the first option above
since PTR_ERR_OR_ZERO() also embeds the first option.
>> +    if (ret)
>> +        goto done;
>> +
>> +    ap_matrix = kzalloc(sizeof(*ap_matrix), GFP_KERNEL);
>> +    if (!ap_matrix) {
>> +        ret = -ENOMEM;
>> +        goto matrix_alloc_err;
>> +    }
>> +
>> +    ap_matrix->device.type = &vfio_ap_dev_type;
>> +    dev_set_name(&ap_matrix->device, "%s", VFIO_AP_DEV_NAME);
>> +    ap_matrix->device.parent = vfio_ap_root_device;
>> +    ap_matrix->device.release = vfio_ap_matrix_dev_release;
>> +    ap_matrix->device.driver = &vfio_ap_drv.driver;
>> +
>> +    ret = device_register(&ap_matrix->device);
>> +    if (ret)
>> +        goto matrix_reg_err;
>> +
>> +    goto done;
>> +
>> +matrix_reg_err:
>> +    put_device(&ap_matrix->device);
>> +    kfree(ap_matrix);
>> +
>> +matrix_alloc_err:
>> +    root_device_unregister(vfio_ap_root_device);
>> +
>> +done:
>> +    return ret;
>> +}
>> +
>> +static void vfio_ap_matrix_dev_destroy(struct ap_matrix *ap_matrix)
>> +{
>> +    device_unregister(&ap_matrix->device);
>> +    root_device_unregister(vfio_ap_root_device);
>> +}
>> +
>> +int __init vfio_ap_init(void)
>> +{
>> +    int ret;
>> +
>> +    ret = vfio_ap_matrix_dev_create();
>> +    if (ret)
>> +        return ret;
>> +
>> +    memset(&vfio_ap_drv, 0, sizeof(vfio_ap_drv));
>> +    vfio_ap_drv.probe = vfio_ap_queue_dev_probe;
>> +    vfio_ap_drv.ids = ap_queue_ids;
>> +
>> +    ret = ap_driver_register(&vfio_ap_drv, THIS_MODULE, 
>> VFIO_AP_DRV_NAME);
>> +    if (ret) {
>> +        vfio_ap_matrix_dev_destroy(ap_matrix);
>> +        return ret;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +void __exit vfio_ap_exit(void)
>> +{
>> +    ap_driver_unregister(&vfio_ap_drv);
>> +    vfio_ap_matrix_dev_destroy(ap_matrix);
>> +}
>> +
>> +module_init(vfio_ap_init);
>> +module_exit(vfio_ap_exit);
>> diff --git a/drivers/s390/crypto/vfio_ap_private.h 
>> b/drivers/s390/crypto/vfio_ap_private.h
>> new file mode 100644
>> index 0000000..3505947
>> --- /dev/null
>> +++ b/drivers/s390/crypto/vfio_ap_private.h
>> @@ -0,0 +1,20 @@
>> +/*
>> + * Private data and functions for adjunct processor VFIO matrix driver.
>> + *
>> + * Copyright IBM Corp. 2017
>> + * Author(s): Tony Krowiak <akrowiak@...ux.vnet.ibm.com>
>> + */
>> +
>> +#ifndef _VFIO_AP_PRIVATE_H_
>> +#define _VFIO_AP_PRIVATE_H_
>> +
>> +#include <linux/types.h>
>> +
>> +#define VFIO_AP_MODULE_NAME "vfio_ap"
>> +#define VFIO_AP_DRV_NAME "vfio_ap"
>> +
>> +struct ap_matrix {
>> +    struct device device;
>> +};
>> +
>> +#endif /* _VFIO_AP_PRIVATE_H_ */
>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>> index e3301db..cf2a5e9 100644
>> --- a/include/uapi/linux/vfio.h
>> +++ b/include/uapi/linux/vfio.h
>> @@ -200,6 +200,7 @@ struct vfio_device_info {
>>   #define VFIO_DEVICE_FLAGS_PLATFORM (1 << 2)    /* vfio-platform 
>> device */
>>   #define VFIO_DEVICE_FLAGS_AMBA  (1 << 3)    /* vfio-amba device */
>>   #define VFIO_DEVICE_FLAGS_CCW    (1 << 4)    /* vfio-ccw device */
>> +#define VFIO_DEVICE_FLAGS_AP    (1 << 5)    /* vfio-ap device */
>>       __u32    num_regions;    /* Max region index + 1 */
>>       __u32    num_irqs;    /* Max IRQ index + 1 */
>>   };
>> @@ -215,6 +216,7 @@ struct vfio_device_info {
>>   #define VFIO_DEVICE_API_PLATFORM_STRING        "vfio-platform"
>>   #define VFIO_DEVICE_API_AMBA_STRING        "vfio-amba"
>>   #define VFIO_DEVICE_API_CCW_STRING        "vfio-ccw"
>> +#define VFIO_DEVICE_API_AP_STRING        "vfio-ap"
>>
>>   /**
>>    * VFIO_DEVICE_GET_REGION_INFO - _IOWR(VFIO_TYPE, VFIO_BASE + 8,
>
>

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