Re: [PATCH v3 05/14] s390: vfio-ap: base implementation of VFIO AP device driver

From: Tony Krowiak
Date: Thu Mar 15 2018 - 13:26:07 EST


On 03/15/2018 09:25 AM, Pierre Morel wrote:
On 14/03/2018 19:25, 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@xxxxxxxxxxxxxxxxxx>
---
MAINTAINERS | 2 +
arch/s390/Kconfig | 11 +++
drivers/s390/crypto/Makefile | 4 +
drivers/s390/crypto/vfio_ap_drv.c | 135 +++++++++++++++++++++++++++++++++
drivers/s390/crypto/vfio_ap_private.h | 22 ++++++
include/uapi/linux/vfio.h | 2 +
6 files changed, 176 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 72742d5..f129253 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@xxxxxxxxxxxxxxxxxx>
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index cbe1d97..58509db 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -771,6 +771,17 @@ 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
not sure it must be module by default.
I would not set it by default.
Connie also asked about this in the last review, so I will go ahead
and change it.

+ prompt "VFIO support for AP devices"
+ depends on ZCRYPT && VFIO_MDEV_DEVICE

VFIO_MDEV_DEVICE is a general feature *needed* by VFIO_AP
and has no use case by its own. If it is set it is obviously because some
mediated device drivers needs it.
while ZCRYPT is a Z feature which may be set without VFIO_AP.

So you need:

config VFIO_AP
def_tristate n
prompt "VFIO support for AP devices"
depends on ZCRYPT
select VFIO_MDEV
select VFIO_MDEV_DEVICE
...
I was thinking the same just yesterday and I agree, this makes sense.



Pierre