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

[Eric Auger]

Hi Zhenzhong,
On 10/8/23 12:21, Duan, Zhenzhong wrote:
> 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.
OK I removed it.
>
>> +    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.
But this mathes vfio_ccw_get_device() existing code where
vcdev->vdev.name = name; and
name = g_strdup_printf("%x.%x.%04x", cdev->hostid.cssid,
                                 cdev->hostid.ssid,
                                 cdev->hostid.devid);

cdev->mdevid is passed as first arg of vfio_attach_device() instead .

i think this also matches
https://lore.kernel.org/all/PH7PR11MB67222DD282F98E03095FBA8A92C1A@PH7PR11MB6722.namprd11.prod.outlook.com/
no?

Thanks

Eric

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