[PATCH v4 6/8] vfio-ccw: Introduce a new CRW region

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

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

This region provides a mechanism to pass a Channel Report Word
that affect vfio-ccw devices, and needs to be passed to the guest
for its awareness and/or processing.

The base driver (see crw_collect_info()) provides space for two
CRWs, as a subchannel event may have two CRWs chained together
(one for the ssid, one for the subchannel). As vfio-ccw will
deal with everything at the subchannel level, provide space
for a single CRW to be transferred in one shot.

Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
Signed-off-by: Eric Farman <farman@linux.ibm.com>
---

Notes:
v3->v4:
- Move crw_trigger and CRW_IRQ from later patch to here [EF]
- Cleanup descriptions of sizeof CRW region in doc, commentary,
and commit description [CH]
- Clear crw when finished [CH]

v2->v3:
- Remove "if list-empty" check, since there's no list yet [EF]
- Reduce the CRW region to one fullword, instead of two [CH]

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

v0->v1: [EF]
- Clean up checkpatch (whitespace) errors
- Add ret=-ENOMEM in error path for new region
- Add io_mutex for region read (originally in last patch)
- Change crw1/crw2 to crw0/crw1
- Reorder cleanup of regions

Documentation/s390/vfio-ccw.rst | 19 ++++++++++
drivers/s390/cio/vfio_ccw_chp.c | 55 +++++++++++++++++++++++++++++
drivers/s390/cio/vfio_ccw_drv.c | 20 +++++++++++
drivers/s390/cio/vfio_ccw_ops.c | 8 +++++
drivers/s390/cio/vfio_ccw_private.h | 4 +++
include/uapi/linux/vfio.h | 2 ++
include/uapi/linux/vfio_ccw.h | 8 +++++
7 files changed, 116 insertions(+)

diff --git a/Documentation/s390/vfio-ccw.rst b/Documentation/s390/vfio-ccw.rst
index 98832d95f395..da3a9e22663d 100644
--- a/Documentation/s390/vfio-ccw.rst
+++ b/Documentation/s390/vfio-ccw.rst
@@ -247,6 +247,25 @@ 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 crw region
+---------------------
+
+The vfio-ccw crw region is used to return Channel Report Word (CRW)
+data to userspace::
+
+ struct ccw_crw_region {
+ __u32 crw;
+ } __packed;
+
+This region is exposed via region type VFIO_REGION_SUBTYPE_CCW_CRW.
+
+Reading this region returns a CRW if one that is relevant for this
+subchannel (e.g. one reporting changes in channel path state) is
+pending, or all zeroes if not. If multiple CRWs are pending (including
+possibly chained CRWs), reading this region again will return the next
+one, until no more CRWs are pending and zeroes are returned. This is
+similar to how STORE CHANNEL REPORT WORD works.
+
vfio-ccw operation details
--------------------------

diff --git a/drivers/s390/cio/vfio_ccw_chp.c b/drivers/s390/cio/vfio_ccw_chp.c
index 18f3b3e873a9..37ea344a4d72 100644
--- a/drivers/s390/cio/vfio_ccw_chp.c
+++ b/drivers/s390/cio/vfio_ccw_chp.c
@@ -74,3 +74,58 @@ int vfio_ccw_register_schib_dev_regions(struct vfio_ccw_private *private)
VFIO_REGION_INFO_FLAG_READ,
private->schib_region);
}
+
+static ssize_t vfio_ccw_crw_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_crw_region *region;
+ int ret;
+
+ if (pos + count > sizeof(*region))
+ return -EINVAL;
+
+ mutex_lock(&private->io_mutex);
+ region = private->region[i].data;
+
+ if (copy_to_user(buf, (void *)region + pos, count))
+ ret = -EFAULT;
+ else
+ ret = count;
+
+ region->crw = 0;
+
+ mutex_unlock(&private->io_mutex);
+ return ret;
+}
+
+static ssize_t vfio_ccw_crw_region_write(struct vfio_ccw_private *private,
+ const char __user *buf, size_t count,
+ loff_t *ppos)
+{
+ return -EINVAL;
+}
+
+static void vfio_ccw_crw_region_release(struct vfio_ccw_private *private,
+ struct vfio_ccw_region *region)
+{
+
+}
+
+const struct vfio_ccw_regops vfio_ccw_crw_region_ops = {
+ .read = vfio_ccw_crw_region_read,
+ .write = vfio_ccw_crw_region_write,
+ .release = vfio_ccw_crw_region_release,
+};
+
+int vfio_ccw_register_crw_dev_regions(struct vfio_ccw_private *private)
+{
+ return vfio_ccw_register_dev_region(private,
+ VFIO_REGION_SUBTYPE_CCW_CRW,
+ &vfio_ccw_crw_region_ops,
+ sizeof(struct ccw_crw_region),
+ VFIO_REGION_INFO_FLAG_READ,
+ private->crw_region);
+}
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index 7aeff42f370d..e4deae6fd525 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -28,6 +28,7 @@ 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;
+static struct kmem_cache *vfio_ccw_crw_region;

debug_info_t *vfio_ccw_debug_msg_id;
debug_info_t *vfio_ccw_debug_trace_id;
@@ -120,6 +121,8 @@ static void vfio_ccw_sch_irq(struct subchannel *sch)

static void vfio_ccw_free_regions(struct vfio_ccw_private *private)
{
+ if (private->crw_region)
+ kmem_cache_free(vfio_ccw_crw_region, private->crw_region);
if (private->schib_region)
kmem_cache_free(vfio_ccw_schib_region, private->schib_region);
if (private->cmd_region)
@@ -165,6 +168,12 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
if (!private->schib_region)
goto out_free;

+ private->crw_region = kmem_cache_zalloc(vfio_ccw_crw_region,
+ GFP_KERNEL | GFP_DMA);
+
+ if (!private->crw_region)
+ goto out_free;
+
private->sch = sch;
dev_set_drvdata(&sch->dev, private);
mutex_init(&private->io_mutex);
@@ -366,6 +375,7 @@ static void vfio_ccw_debug_exit(void)

static void vfio_ccw_destroy_regions(void)
{
+ kmem_cache_destroy(vfio_ccw_crw_region);
kmem_cache_destroy(vfio_ccw_schib_region);
kmem_cache_destroy(vfio_ccw_cmd_region);
kmem_cache_destroy(vfio_ccw_io_region);
@@ -413,6 +423,16 @@ static int __init vfio_ccw_sch_init(void)
goto out_err;
}

+ vfio_ccw_crw_region = kmem_cache_create_usercopy("vfio_ccw_crw_region",
+ sizeof(struct ccw_crw_region), 0,
+ SLAB_ACCOUNT, 0,
+ sizeof(struct ccw_crw_region), NULL);
+
+ if (!vfio_ccw_crw_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 c3a74ab7bb86..8b3ed5b45277 100644
--- a/drivers/s390/cio/vfio_ccw_ops.c
+++ b/drivers/s390/cio/vfio_ccw_ops.c
@@ -178,6 +178,10 @@ static int vfio_ccw_mdev_open(struct mdev_device *mdev)
if (ret)
goto out_unregister;

+ ret = vfio_ccw_register_crw_dev_regions(private);
+ if (ret)
+ goto out_unregister;
+
return ret;

out_unregister:
@@ -389,6 +393,7 @@ static int vfio_ccw_mdev_get_irq_info(struct vfio_irq_info *info)
{
switch (info->index) {
case VFIO_CCW_IO_IRQ_INDEX:
+ case VFIO_CCW_CRW_IRQ_INDEX:
info->count = 1;
info->flags = VFIO_IRQ_INFO_EVENTFD;
break;
@@ -416,6 +421,9 @@ static int vfio_ccw_mdev_set_irqs(struct mdev_device *mdev,
case VFIO_CCW_IO_IRQ_INDEX:
ctx = &private->io_trigger;
break;
+ case VFIO_CCW_CRW_IRQ_INDEX:
+ ctx = &private->crw_trigger;
+ break;
default:
return -EINVAL;
}
diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
index d6601a8adf13..97131b4df0b9 100644
--- a/drivers/s390/cio/vfio_ccw_private.h
+++ b/drivers/s390/cio/vfio_ccw_private.h
@@ -57,6 +57,7 @@ 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);
+int vfio_ccw_register_crw_dev_regions(struct vfio_ccw_private *private);

/**
* struct vfio_ccw_private
@@ -71,6 +72,7 @@ int vfio_ccw_register_schib_dev_regions(struct vfio_ccw_private *private);
* @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
+ * @crw_region: MMIO region for getting channel report words
* @num_regions: number of additional regions
* @cp: channel program for the current I/O operation
* @irb: irb info received from interrupt
@@ -90,6 +92,7 @@ struct vfio_ccw_private {
struct vfio_ccw_region *region;
struct ccw_cmd_region *cmd_region;
struct ccw_schib_region *schib_region;
+ struct ccw_crw_region *crw_region;
int num_regions;

struct channel_program cp;
@@ -97,6 +100,7 @@ struct vfio_ccw_private {
union scsw scsw;

struct eventfd_ctx *io_trigger;
+ struct eventfd_ctx *crw_trigger;
struct work_struct io_work;
} __aligned(8);

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 7a1abbd889bd..907758cf6d60 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -379,6 +379,7 @@ 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)
+#define VFIO_REGION_SUBTYPE_CCW_CRW (3)

/*
* The MSIX mappable capability informs that MSIX data of a BAR can be mmapped
@@ -578,6 +579,7 @@ enum {

enum {
VFIO_CCW_IO_IRQ_INDEX,
+ VFIO_CCW_CRW_IRQ_INDEX,
VFIO_CCW_NUM_IRQS
};

diff --git a/include/uapi/linux/vfio_ccw.h b/include/uapi/linux/vfio_ccw.h
index 758bf214898d..cff5076586df 100644
--- a/include/uapi/linux/vfio_ccw.h
+++ b/include/uapi/linux/vfio_ccw.h
@@ -44,4 +44,12 @@ struct ccw_schib_region {
__u8 schib_area[SCHIB_AREA_SIZE];
} __packed;

+/*
+ * Used for returning a Channel Report Word to userspace.
+ * Note: this is controlled by a capability
+ */
+struct ccw_crw_region {
+ __u32 crw;
+} __packed;
+
#endif
--
2.17.1