RE: [PATCH v4 10/15] vfio/ccw: Use vfio_[attach/detach]_device

[Duan, Zhenzhong]

Hi Eric,

>-----Original Message-----
>From: Eric Auger <eric.auger@redhat.com>
>Sent: Wednesday, October 4, 2023 11:44 PM
>Subject: [PATCH v4 10/15] vfio/ccw: Use vfio_[attach/detach]_device
>
>Let the vfio-ccw device use vfio_attach_device() and
>vfio_detach_device(), hence hiding the details of the used
>IOMMU backend.
>
>Note that the migration reduces the following trace
>"vfio: subchannel %s has already been attached" (featuring
>cssid.ssid.devid) into "device is already attached"
>
>Also now all the devices have been migrated to use the new
>vfio_attach_device/vfio_detach_device API, let's turn the
>legacy functions into static functions, local to container.c.
>
>Signed-off-by: Eric Auger <eric.auger@redhat.com>
>Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
>
>---
>
>v3:
>- simplified vbasedev->dev setting
>
>v2 -> v3:
>- Hopefully fix confusion beteen vbasedev->name, mdevid and sysfsdev
>  while keeping into account Matthew's comment
>  https://lore.kernel.org/qemu-devel/6e04ab8f-dc84-e9c2-deea-
>2b6b31678b53@linux.ibm.com/
>---
> include/hw/vfio/vfio-common.h |   5 --
> hw/vfio/ccw.c                 | 122 +++++++++-------------------------
> hw/vfio/common.c              |  10 +--
> 3 files changed, 37 insertions(+), 100 deletions(-)
>
>diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>index 12fbfbc37d..c486bdef2a 100644
>--- a/include/hw/vfio/vfio-common.h
>+++ b/include/hw/vfio/vfio-common.h
>@@ -202,7 +202,6 @@ typedef struct {
>     hwaddr pages;
> } VFIOBitmap;
>
>-void vfio_put_base_device(VFIODevice *vbasedev);
> void vfio_disable_irqindex(VFIODevice *vbasedev, int index);
> void vfio_unmask_single_irqindex(VFIODevice *vbasedev, int index);
> void vfio_mask_single_irqindex(VFIODevice *vbasedev, int index);
>@@ -220,11 +219,7 @@ void vfio_region_unmap(VFIORegion *region);
> void vfio_region_exit(VFIORegion *region);
> void vfio_region_finalize(VFIORegion *region);
> void vfio_reset_handler(void *opaque);
>-VFIOGroup *vfio_get_group(int groupid, AddressSpace *as, Error **errp);
>-void vfio_put_group(VFIOGroup *group);
> struct vfio_device_info *vfio_get_device_info(int fd);
>-int vfio_get_device(VFIOGroup *group, const char *name,
>-                    VFIODevice *vbasedev, Error **errp);
> int vfio_attach_device(char *name, VFIODevice *vbasedev,
>                        AddressSpace *as, Error **errp);
> void vfio_detach_device(VFIODevice *vbasedev);
>diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
>index 1e2fce83b0..6ec35fedc9 100644
>--- a/hw/vfio/ccw.c
>+++ b/hw/vfio/ccw.c
>@@ -572,88 +572,15 @@ static void vfio_ccw_put_region(VFIOCCWDevice
>*vcdev)
>     g_free(vcdev->io_region);
> }
>
>-static void vfio_ccw_put_device(VFIOCCWDevice *vcdev)
>-{
>-    g_free(vcdev->vdev.name);
>-    vfio_put_base_device(&vcdev->vdev);
>-}
>-
>-static void vfio_ccw_get_device(VFIOGroup *group, VFIOCCWDevice *vcdev,
>-                                Error **errp)
>-{
>-    S390CCWDevice *cdev = S390_CCW_DEVICE(vcdev);
>-    char *name = g_strdup_printf("%x.%x.%04x", cdev->hostid.cssid,
>-                                 cdev->hostid.ssid,
>-                                 cdev->hostid.devid);
>-    VFIODevice *vbasedev;
>-
>-    QLIST_FOREACH(vbasedev, &group->device_list, next) {
>-        if (strcmp(vbasedev->name, name) == 0) {
>-            error_setg(errp, "vfio: subchannel %s has already been attached",
>-                       name);
>-            goto out_err;
>-        }
>-    }
>-
>-    /*
>-     * All vfio-ccw devices are believed to operate in a way compatible with
>-     * discarding of memory in RAM blocks, ie. pages pinned in the host are
>-     * in the current working set of the guest driver and therefore never
>-     * overlap e.g., with pages available to the guest balloon driver.  This
>-     * needs to be set before vfio_get_device() for vfio common to handle
>-     * ram_block_discard_disable().
>-     */
>-    vcdev->vdev.ram_block_discard_allowed = true;
>-
>-    if (vfio_get_device(group, cdev->mdevid, &vcdev->vdev, errp)) {
>-        goto out_err;
>-    }
>-
>-    vcdev->vdev.ops = &vfio_ccw_ops;
>-    vcdev->vdev.type = VFIO_DEVICE_TYPE_CCW;
>-    vcdev->vdev.name = name;
>-    vcdev->vdev.dev = DEVICE(vcdev);
>-
>-    return;
>-
>-out_err:
>-    g_free(name);
>-}
>-
>-static VFIOGroup *vfio_ccw_get_group(S390CCWDevice *cdev, Error **errp)
>-{
>-    char *tmp, group_path[PATH_MAX];
>-    ssize_t len;
>-    int groupid;
>-
>-    tmp = g_strdup_printf("/sys/bus/css/devices/%x.%x.%04x/%s/iommu_group",
>-                          cdev->hostid.cssid, cdev->hostid.ssid,
>-                          cdev->hostid.devid, cdev->mdevid);
>-    len = readlink(tmp, group_path, sizeof(group_path));
>-    g_free(tmp);
>-
>-    if (len <= 0 || len >= sizeof(group_path)) {
>-        error_setg(errp, "vfio: no iommu_group found");
>-        return NULL;
>-    }
>-
>-    group_path[len] = 0;
>-
>-    if (sscanf(basename(group_path), "%d", &groupid) != 1) {
>-        error_setg(errp, "vfio: failed to read %s", group_path);
>-        return NULL;
>-    }
>-
>-    return vfio_get_group(groupid, &address_space_memory, errp);
>-}
>-
> static void vfio_ccw_realize(DeviceState *dev, Error **errp)
> {
>-    VFIOGroup *group;
>     S390CCWDevice *cdev = S390_CCW_DEVICE(dev);
>     VFIOCCWDevice *vcdev = VFIO_CCW(cdev);
>     S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
>+    VFIODevice *vbasedev = &vcdev->vdev;
>     Error *err = NULL;
>+    char *name;
>+    int ret;
>
>     /* Call the class init function for subchannel. */
>     if (cdc->realize) {
>@@ -663,14 +590,31 @@ static void vfio_ccw_realize(DeviceState *dev, Error
>**errp)
>         }
>     }
>
>-    group = vfio_ccw_get_group(cdev, &err);
>-    if (!group) {
>-        goto out_group_err;
>-    }
>+    name = g_strdup_printf("%x.%x.%04x", vcdev->cdev.hostid.cssid,
>+                           vcdev->cdev.hostid.ssid,
>+                           vcdev->cdev.hostid.devid);
>+    vbasedev->sysfsdev = g_strdup_printf("/sys/bus/css/devices/%s/%s",
>+                                         name,
>+                                         cdev->mdevid);

Hoping not late for you to include this in v5.
I think no need to re-assign sysfsdev as it's a user property, we'd better to
keep the original user value. Also looks a memory leak here.

>+    vbasedev->ops = &vfio_ccw_ops;
>+    vbasedev->type = VFIO_DEVICE_TYPE_CCW;
>+    vbasedev->name = name;

There will be a potential failure when a second mdev device under
same cssid.ssid.devid attached. We can use cdev->mdevid as name.

Maybe you can use v2 of this patch, I remember these two issues are already 
addressed in v2.

Thanks
Zhenzhong