[PATCH v4 4/8] vfio-ccw: Introduce a new schib region

Eric Farman
2020-05-05T12:27:58Z

From: Farhan Ali <alifm@linux.ibm.com>

The schib region can be used by userspace to get the subchannel-
information block (SCHIB) for the passthrough subchannel.
This can be useful to get information such as channel path
information via the SCHIB.PMCW fields.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
---

Notes:
v3->v4:
- Added Conny's r-b

v2->v3:
- Updated Copyright year and Authors [CH]
- Mention that schib region triggers a STSCH [CH]

v1->v2:
- Add new region info to Documentation/s390/vfio-ccw.rst [CH]
- Add a block comment to struct ccw_schib_region [CH]

v0->v1: [EF]
- Clean up checkpatch (#include, whitespace) errors
- Remove unnecessary includes from vfio_ccw_chp.c
- Add ret=-ENOMEM in error path for new region
- Add call to vfio_ccw_unregister_dev_regions() during error exit
path of vfio_ccw_mdev_open()
- New info on the module prologue
- Reorder cleanup of regions

Documentation/s390/vfio-ccw.rst | 19 +++++++-
drivers/s390/cio/Makefile | 2 +-
drivers/s390/cio/vfio_ccw_chp.c | 76 +++++++++++++++++++++++++++++
drivers/s390/cio/vfio_ccw_drv.c | 20 ++++++++
drivers/s390/cio/vfio_ccw_ops.c | 14 +++++-
drivers/s390/cio/vfio_ccw_private.h | 3 ++
include/uapi/linux/vfio.h | 1 +
include/uapi/linux/vfio_ccw.h | 10 ++++
8 files changed, 141 insertions(+), 4 deletions(-)
create mode 100644 drivers/s390/cio/vfio_ccw_chp.c

diff --git a/Documentation/s390/vfio-ccw.rst b/Documentation/s390/vfio-ccw.rst
index fca9c4f5bd9c..98832d95f395 100644
--- a/Documentation/s390/vfio-ccw.rst
+++ b/Documentation/s390/vfio-ccw.rst
@@ -231,6 +231,22 @@ This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD.

Currently, CLEAR SUBCHANNEL and HALT SUBCHANNEL use this region.

+vfio-ccw schib region
+---------------------
+
+The vfio-ccw schib region is used to return Subchannel-Information
+Block (SCHIB) data to userspace::
+
+ struct ccw_schib_region {
+ #define SCHIB_AREA_SIZE 52
+ __u8 schib_area[SCHIB_AREA_SIZE];
+ } __packed;
+
+This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_SCHIB.
+
+Reading this region triggers a STORE SUBCHANNEL to be issued to the
+associated hardware.
+
vfio-ccw operation details
--------------------------

@@ -333,7 +349,8 @@ through DASD/ECKD device online in a guest now and use it as a block
device.

The current code allows the guest to start channel programs via
-START SUBCHANNEL, and to issue HALT SUBCHANNEL and CLEAR SUBCHANNEL.
+START SUBCHANNEL, and to issue HALT SUBCHANNEL, CLEAR SUBCHANNEL,
+and STORE SUBCHANNEL.

vfio-ccw supports classic (command mode) channel I/O only. Transport
mode (HPF) is not supported.
diff --git a/drivers/s390/cio/Makefile b/drivers/s390/cio/Makefile
index 23eae4188876..a9235f111e79 100644
--- a/drivers/s390/cio/Makefile
+++ b/drivers/s390/cio/Makefile
@@ -21,5 +21,5 @@ qdio-objs := qdio_main.o qdio_thinint.o qdio_debug.o qdio_setup.o
obj-$(CONFIG_QDIO) += qdio.o

vfio_ccw-objs += vfio_ccw_drv.o vfio_ccw_cp.o vfio_ccw_ops.o vfio_ccw_fsm.o \
- vfio_ccw_async.o vfio_ccw_trace.o
+ vfio_ccw_async.o vfio_ccw_trace.o vfio_ccw_chp.o
obj-$(CONFIG_VFIO_CCW) += vfio_ccw.o
diff --git a/drivers/s390/cio/vfio_ccw_chp.c b/drivers/s390/cio/vfio_ccw_chp.c
new file mode 100644
index 000000000000..18f3b3e873a9
--- /dev/null
+++ b/drivers/s390/cio/vfio_ccw_chp.c
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Channel path related status regions for vfio_ccw
+ *
+ * Copyright IBM Corp. 2020
+ *
+ * Author(s): Farhan Ali <alifm@linux.ibm.com>
+ * Eric Farman <farman@linux.ibm.com>
+ */
+
+#include <linux/vfio.h>
+#include "vfio_ccw_private.h"
+
+static ssize_t vfio_ccw_schib_region_read(struct vfio_ccw_private *private,
+ char __user *buf, size_t count,
+ loff_t *ppos)
+{
+ unsigned int i = VFIO_CCW_OFFSET_TO_INDEX(*ppos) - VFIO_CCW_NUM_REGIONS;
+ loff_t pos = *ppos & VFIO_CCW_OFFSET_MASK;
+ struct ccw_schib_region *region;
+ int ret;
+
+ if (pos + count > sizeof(*region))
+ return -EINVAL;
+
+ mutex_lock(&private->io_mutex);
+ region = private->region[i].data;
+
+ if (cio_update_schib(private->sch)) {
+ ret = -ENODEV;
+ goto out;
+ }
+
+ memcpy(region, &private->sch->schib, sizeof(*region));
+
+ if (copy_to_user(buf, (void *)region + pos, count)) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ ret = count;
+
+out:
+ mutex_unlock(&private->io_mutex);
+ return ret;
+}
+
+static ssize_t vfio_ccw_schib_region_write(struct vfio_ccw_private *private,
+ const char __user *buf, size_t count,
+ loff_t *ppos)
+{
+ return -EINVAL;
+}
+
+
+static void vfio_ccw_schib_region_release(struct vfio_ccw_private *private,
+ struct vfio_ccw_region *region)
+{
+
+}
+
+const struct vfio_ccw_regops vfio_ccw_schib_region_ops = {
+ .read = vfio_ccw_schib_region_read,
+ .write = vfio_ccw_schib_region_write,
+ .release = vfio_ccw_schib_region_release,
+};
+
+int vfio_ccw_register_schib_dev_regions(struct vfio_ccw_private *private)
+{
+ return vfio_ccw_register_dev_region(private,
+ VFIO_REGION_SUBTYPE_CCW_SCHIB,
+ &vfio_ccw_schib_region_ops,
+ sizeof(struct ccw_schib_region),
+ VFIO_REGION_INFO_FLAG_READ,
+ private->schib_region);
+}
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index fb1275a7d1f5..7aeff42f370d 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -27,6 +27,7 @@
struct workqueue_struct *vfio_ccw_work_q;
static struct kmem_cache *vfio_ccw_io_region;
static struct kmem_cache *vfio_ccw_cmd_region;
+static struct kmem_cache *vfio_ccw_schib_region;

debug_info_t *vfio_ccw_debug_msg_id;
debug_info_t *vfio_ccw_debug_trace_id;
@@ -119,6 +120,8 @@ static void vfio_ccw_sch_irq(struct subchannel *sch)

static void vfio_ccw_free_regions(struct vfio_ccw_private *private)
{
+ if (private->schib_region)
+ kmem_cache_free(vfio_ccw_schib_region, private->schib_region);
if (private->cmd_region)
kmem_cache_free(vfio_ccw_cmd_region, private->cmd_region);
if (private->io_region)
@@ -156,6 +159,12 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
if (!private->cmd_region)
goto out_free;

+ private->schib_region = kmem_cache_zalloc(vfio_ccw_schib_region,
+ GFP_KERNEL | GFP_DMA);
+
+ if (!private->schib_region)
+ goto out_free;
+
private->sch = sch;
dev_set_drvdata(&sch->dev, private);
mutex_init(&private->io_mutex);
@@ -357,6 +366,7 @@ static void vfio_ccw_debug_exit(void)

static void vfio_ccw_destroy_regions(void)
{
+ kmem_cache_destroy(vfio_ccw_schib_region);
kmem_cache_destroy(vfio_ccw_cmd_region);
kmem_cache_destroy(vfio_ccw_io_region);
}
@@ -393,6 +403,16 @@ static int __init vfio_ccw_sch_init(void)
goto out_err;
}

+ vfio_ccw_schib_region = kmem_cache_create_usercopy("vfio_ccw_schib_region",
+ sizeof(struct ccw_schib_region), 0,
+ SLAB_ACCOUNT, 0,
+ sizeof(struct ccw_schib_region), NULL);
+
+ if (!vfio_ccw_schib_region) {
+ ret = -ENOMEM;
+ goto out_err;
+ }
+
isc_register(VFIO_CCW_ISC);
ret = css_driver_register(&vfio_ccw_sch_driver);
if (ret) {
diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
index d4fc84b8867f..22988d67b6bb 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -172,8 +172,18 @@ static int vfio_ccw_mdev_open(struct mdev_device *mdev)

ret = vfio_ccw_register_async_dev_regions(private);
if (ret)
- vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
- &private->nb);
+ goto out_unregister;
+
+ ret = vfio_ccw_register_schib_dev_regions(private);
+ if (ret)
+ goto out_unregister;
+
+ return ret;
+
+out_unregister:
+ vfio_ccw_unregister_dev_regions(private);
+ vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
+ &private->nb);
return ret;
}

diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index ce3834159d98..d6601a8adf13 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -56,6 +56,7 @@ int vfio_ccw_register_dev_region(struct vfio_ccw_private *private,
void vfio_ccw_unregister_dev_regions(struct vfio_ccw_private *private);

int vfio_ccw_register_async_dev_regions(struct vfio_ccw_private *private);
+int vfio_ccw_register_schib_dev_regions(struct vfio_ccw_private *private);

/**
* struct vfio_ccw_private
@@ -69,6 +70,7 @@ int vfio_ccw_register_async_dev_regions(struct vfio_ccw_private *private);
* @io_mutex: protect against concurrent update of I/O regions
* @region: additional regions for other subchannel operations
* @cmd_region: MMIO region for asynchronous I/O commands other than START
+ * @schib_region: MMIO region for SCHIB information
* @num_regions: number of additional regions
* @cp: channel program for the current I/O operation
* @irb: irb info received from interrupt
@@ -87,6 +89,7 @@ struct vfio_ccw_private {
struct mutex io_mutex;
struct vfio_ccw_region *region;
struct ccw_cmd_region *cmd_region;
+ struct ccw_schib_region *schib_region;
int num_regions;

struct channel_program cp;
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 015516bcfaa3..7a1abbd889bd 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -378,6 +378,7 @@ struct vfio_region_gfx_edid {

/* sub-types for VFIO_REGION_TYPE_CCW */
#define VFIO_REGION_SUBTYPE_CCW_ASYNC_CMD (1)
+#define VFIO_REGION_SUBTYPE_CCW_SCHIB (2)

/*
* The MSIX mappable capability informs that MSIX data of a BAR can be mmapped
diff --git a/include/uapi/linux/vfio_ccw.h b/include/uapi/linux/vfio_ccw.h
index cbecbf0cd54f..758bf214898d 100644
--- a/include/uapi/linux/vfio_ccw.h
+++ b/include/uapi/linux/vfio_ccw.h
@@ -34,4 +34,14 @@ struct ccw_cmd_region {
__u32 ret_code;
} __packed;

+/*
+ * Used for processing commands that read the subchannel-information block
+ * Reading this region triggers a stsch() to hardware
+ * Note: this is controlled by a capability
+ */
+struct ccw_schib_region {
+#define SCHIB_AREA_SIZE 52
+ __u8 schib_area[SCHIB_AREA_SIZE];
+} __packed;
+
#endif
--
2.17.1