Re: [PATCH v28 04/17] vfio: Add migration region initialization and finalize function

[Kirti Wankhede <kwankhede@nvidia.com>]

On 10/24/2020 7:51 PM, Alex Williamson wrote:
> On Sat, 24 Oct 2020 15:09:14 +0530
> Kirti Wankhede <kwankhede@nvidia.com> wrote:
> 
>> On 10/23/2020 10:22 PM, Alex Williamson wrote:
>>> On Fri, 23 Oct 2020 16:10:30 +0530
>>> Kirti Wankhede <kwankhede@nvidia.com> wrote:
>>>    
>>>> Whether the VFIO device supports migration or not is decided based of
>>>> migration region query. If migration region query is successful and migration
>>>> region initialization is successful then migration is supported else
>>>> migration is blocked.
>>>>
>>>> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
>>>> Reviewed-by: Neo Jia <cjia@nvidia.com>
>>>> Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>> ---
>>>>    hw/vfio/meson.build           |   1 +
>>>>    hw/vfio/migration.c           | 133 ++++++++++++++++++++++++++++++++++++++++++
>>>>    hw/vfio/trace-events          |   3 +
>>>>    include/hw/vfio/vfio-common.h |   9 +++
>>>>    4 files changed, 146 insertions(+)
>>>>    create mode 100644 hw/vfio/migration.c
>>>>
>>>> diff --git a/hw/vfio/meson.build b/hw/vfio/meson.build
>>>> index 37efa74018bc..da9af297a0c5 100644
>>>> --- a/hw/vfio/meson.build
>>>> +++ b/hw/vfio/meson.build
>>>> @@ -2,6 +2,7 @@ vfio_ss = ss.source_set()
>>>>    vfio_ss.add(files(
>>>>      'common.c',
>>>>      'spapr.c',
>>>> +  'migration.c',
>>>>    ))
>>>>    vfio_ss.add(when: 'CONFIG_VFIO_PCI', if_true: files(
>>>>      'display.c',
>>>> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c
>>>> new file mode 100644
>>>> index 000000000000..bbe6e0b7a6cc
>>>> --- /dev/null
>>>> +++ b/hw/vfio/migration.c
>>>> @@ -0,0 +1,133 @@
>>>> +/*
>>>> + * Migration support for VFIO devices
>>>> + *
>>>> + * Copyright NVIDIA, Inc. 2020
>>>> + *
>>>> + * This work is licensed under the terms of the GNU GPL, version 2. See
>>>> + * the COPYING file in the top-level directory.
>>>> + */
>>>> +
>>>> +#include "qemu/osdep.h"
>>>> +#include <linux/vfio.h>
>>>> +
>>>> +#include "hw/vfio/vfio-common.h"
>>>> +#include "cpu.h"
>>>> +#include "migration/migration.h"
>>>> +#include "migration/qemu-file.h"
>>>> +#include "migration/register.h"
>>>> +#include "migration/blocker.h"
>>>> +#include "migration/misc.h"
>>>> +#include "qapi/error.h"
>>>> +#include "exec/ramlist.h"
>>>> +#include "exec/ram_addr.h"
>>>> +#include "pci.h"
>>>> +#include "trace.h"
>>>> +
>>>> +static void vfio_migration_region_exit(VFIODevice *vbasedev)
>>>> +{
>>>> +    VFIOMigration *migration = vbasedev->migration;
>>>> +
>>>> +    if (!migration) {
>>>> +        return;
>>>> +    }
>>>> +
>>>> +    vfio_region_exit(&migration->region);
>>>> +    vfio_region_finalize(&migration->region);
>>>
>>> I think it would make sense to also:
>>>
>>> g_free(migration);
>>> vbasedev->migration = NULL;
>>>
>>> here as well so the callers don't need to.
>>
>> No, vfio_migration_init() case, err case is also hit when
>> vbasedev->migration is not yet set but local variable migration is not-NULL.
> 
> So why do we even call vfio_migration_region_exit() for that error
> case?  It seems that could just g_free(migration); return ret; rather
> than goto err.  Thanks,
> 

Removing temporary local variable, with that above 2 can be moved to 
exit function.

Thanks,
Kirti

> Alex
> 
>>> Not worth a re-spin itself,
>>> maybe a follow-up if there's no other reason for a re-spin.  Thanks,
>>>
>>> Alex
>>>    
>>>> +}
>>>> +
>>>> +static int vfio_migration_init(VFIODevice *vbasedev,
>>>> +                               struct vfio_region_info *info)
>>>> +{
>>>> +    int ret;
>>>> +    Object *obj;
>>>> +    VFIOMigration *migration;
>>>> +
>>>> +    if (!vbasedev->ops->vfio_get_object) {
>>>> +        return -EINVAL;
>>>> +    }
>>>> +
>>>> +    obj = vbasedev->ops->vfio_get_object(vbasedev);
>>>> +    if (!obj) {
>>>> +        return -EINVAL;
>>>> +    }
>>>> +
>>>> +    migration = g_new0(VFIOMigration, 1);
>>>> +
>>>> +    ret = vfio_region_setup(obj, vbasedev, &migration->region,
>>>> +                            info->index, "migration");
>>>> +    if (ret) {
>>>> +        error_report("%s: Failed to setup VFIO migration region %d: %s",
>>>> +                     vbasedev->name, info->index, strerror(-ret));
>>>> +        goto err;
>>>> +    }
>>>> +
>>>> +    vbasedev->migration = migration;
>>>> +
>>>> +    if (!migration->region.size) {
>>>> +        error_report("%s: Invalid zero-sized of VFIO migration region %d",
>>>> +                     vbasedev->name, info->index);
>>>> +        ret = -EINVAL;
>>>> +        goto err;
>>>> +    }
>>>> +    return 0;
>>>> +
>>>> +err:
>>>> +    vfio_migration_region_exit(vbasedev);
>>>> +    g_free(migration);
>>>> +    vbasedev->migration = NULL;
>>>> +    return ret;
>>>> +}
>>>> +
>>>> +/* ---------------------------------------------------------------------- */
>>>> +
>>>> +int vfio_migration_probe(VFIODevice *vbasedev, Error **errp)
>>>> +{
>>>> +    struct vfio_region_info *info = NULL;
>>>> +    Error *local_err = NULL;
>>>> +    int ret;
>>>> +
>>>> +    ret = vfio_get_dev_region_info(vbasedev, VFIO_REGION_TYPE_MIGRATION,
>>>> +                                   VFIO_REGION_SUBTYPE_MIGRATION, &info);
>>>> +    if (ret) {
>>>> +        goto add_blocker;
>>>> +    }
>>>> +
>>>> +    ret = vfio_migration_init(vbasedev, info);
>>>> +    if (ret) {
>>>> +        goto add_blocker;
>>>> +    }
>>>> +
>>>> +    g_free(info);
>>>> +    trace_vfio_migration_probe(vbasedev->name, info->index);
>>>> +    return 0;
>>>> +
>>>> +add_blocker:
>>>> +    error_setg(&vbasedev->migration_blocker,
>>>> +               "VFIO device doesn't support migration");
>>>> +    g_free(info);
>>>> +
>>>> +    ret = migrate_add_blocker(vbasedev->migration_blocker, &local_err);
>>>> +    if (local_err) {
>>>> +        error_propagate(errp, local_err);
>>>> +        error_free(vbasedev->migration_blocker);
>>>> +        vbasedev->migration_blocker = NULL;
>>>> +    }
>>>> +    return ret;
>>>> +}
>>>> +
>>>> +void vfio_migration_finalize(VFIODevice *vbasedev)
>>>> +{
>>>> +    VFIOMigration *migration = vbasedev->migration;
>>>> +
>>>> +    if (migration) {
>>>> +        vfio_migration_region_exit(vbasedev);
>>>> +        g_free(vbasedev->migration);
>>>> +        vbasedev->migration = NULL;
>>>> +    }
>>>> +
>>>> +    if (vbasedev->migration_blocker) {
>>>> +        migrate_del_blocker(vbasedev->migration_blocker);
>>>> +        error_free(vbasedev->migration_blocker);
>>>> +        vbasedev->migration_blocker = NULL;
>>>> +    }
>>>> +}
>>>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>>>> index a0c7b49a2ebc..9ced5ec6277c 100644
>>>> --- a/hw/vfio/trace-events
>>>> +++ b/hw/vfio/trace-events
>>>> @@ -145,3 +145,6 @@ vfio_display_edid_link_up(void) ""
>>>>    vfio_display_edid_link_down(void) ""
>>>>    vfio_display_edid_update(uint32_t prefx, uint32_t prefy) "%ux%u"
>>>>    vfio_display_edid_write_error(void) ""
>>>> +
>>>> +# migration.c
>>>> +vfio_migration_probe(const char *name, uint32_t index) " (%s) Region %d"
>>>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>>>> index ba6169cd926e..8275c4c68f45 100644
>>>> --- a/include/hw/vfio/vfio-common.h
>>>> +++ b/include/hw/vfio/vfio-common.h
>>>> @@ -57,6 +57,10 @@ typedef struct VFIORegion {
>>>>        uint8_t nr; /* cache the region number for debug */
>>>>    } VFIORegion;
>>>>    
>>>> +typedef struct VFIOMigration {
>>>> +    VFIORegion region;
>>>> +} VFIOMigration;
>>>> +
>>>>    typedef struct VFIOAddressSpace {
>>>>        AddressSpace *as;
>>>>        QLIST_HEAD(, VFIOContainer) containers;
>>>> @@ -113,6 +117,8 @@ typedef struct VFIODevice {
>>>>        unsigned int num_irqs;
>>>>        unsigned int num_regions;
>>>>        unsigned int flags;
>>>> +    VFIOMigration *migration;
>>>> +    Error *migration_blocker;
>>>>    } VFIODevice;
>>>>    
>>>>    struct VFIODeviceOps {
>>>> @@ -204,4 +210,7 @@ int vfio_spapr_create_window(VFIOContainer *container,
>>>>    int vfio_spapr_remove_window(VFIOContainer *container,
>>>>                                 hwaddr offset_within_address_space);
>>>>    
>>>> +int vfio_migration_probe(VFIODevice *vbasedev, Error **errp);
>>>> +void vfio_migration_finalize(VFIODevice *vbasedev);
>>>> +
>>>>    #endif /* HW_VFIO_VFIO_COMMON_H */
>>>    
>>
>