Re: [PATCH v26 04/17] vfio: Add migration region initialization and finalize function

[Kirti Wankhede <kwankhede@nvidia.com>]

On 9/26/2020 1:50 AM, Alex Williamson wrote:
> On Wed, 23 Sep 2020 04:54:06 +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           | 142 ++++++++++++++++++++++++++++++++++++++++++
>>   hw/vfio/trace-events          |   5 ++
>>   include/hw/vfio/vfio-common.h |   9 +++
>>   4 files changed, 157 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..2f760f1f9c47
>> --- /dev/null
>> +++ b/hw/vfio/migration.c
>> @@ -0,0 +1,142 @@
>> +/*
>> + * 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;
>> +    }
>> +
>> +    if (migration->region.size) {
>> +        vfio_region_exit(&migration->region);
>> +        vfio_region_finalize(&migration->region);
>> +    }
>> +}
>> +
>> +static int vfio_migration_region_init(VFIODevice *vbasedev, int index)
>> +{
>> +    VFIOMigration *migration = vbasedev->migration;
>> +    Object *obj = NULL;
> 
> Unnecessary initialization.
> 
>> +    int ret = -EINVAL;
> 
> return -EINVAL below, this doesn't need to be initialized, use it for
> storing actual return values.
> 
>> +
>> +    obj = vbasedev->ops->vfio_get_object(vbasedev);
>> +    if (!obj) {
>> +        return ret;
>> +    }
> 
> vfio_migration_init() tests whether the vbasedev->ops supports
> vfio_get_object, then calls this, then calls vfio_get_object itself
> (added in a later patch, with a strange inconsistency in failure modes).
> Wouldn't it make more sense for vfio_migration_init() to pass the
> Object since that function also needs it (eventually) and actually does
> the existence test?
> 
>> +
>> +    ret = vfio_region_setup(obj, vbasedev, &migration->region, index,
>> +                            "migration");
>> +    if (ret) {
>> +        error_report("%s: Failed to setup VFIO migration region %d: %s",
>> +                     vbasedev->name, index, strerror(-ret));
>> +        goto err;
>> +    }
>> +
>> +    if (!migration->region.size) {
>> +        ret = -EINVAL;
>> +        error_report("%s: Invalid region size of VFIO migration region %d: %s",
>> +                     vbasedev->name, index, strerror(-ret));
>> +        goto err;
>> +    }
> 
> If the caller were to pass obj, this is nothing more than a wrapper for
> calling vfio_region_setup(), which suggests to me we might not even
> need this as a separate function outside of vfio_migration_init().
> 

Removed vfio_migration_region_init(), moving vfio_region_setup() to
vfio_migration_init()

Thanks,
Kirti

>> +
>> +    return 0;
>> +
>> +err:
>> +    vfio_migration_region_exit(vbasedev);
>> +    return ret;
>> +}
>> +
>> +static int vfio_migration_init(VFIODevice *vbasedev,
>> +                               struct vfio_region_info *info)
>> +{
>> +    int ret = -EINVAL;
>> +
>> +    if (!vbasedev->ops->vfio_get_object) {
>> +        return ret;
>> +    }
>> +
>> +    vbasedev->migration = g_new0(VFIOMigration, 1);
>> +
>> +    ret = vfio_migration_region_init(vbasedev, info->index);
>> +    if (ret) {
>> +        error_report("%s: Failed to initialise migration region",
>> +                     vbasedev->name);
>> +        g_free(vbasedev->migration);
>> +        vbasedev->migration = NULL;
>> +    }
>> +
>> +    return ret;
>> +}
>> +
>> +/* ---------------------------------------------------------------------- */
>> +
>> +int vfio_migration_probe(VFIODevice *vbasedev, Error **errp)
>> +{
>> +    struct vfio_region_info *info = NULL;
> 
> Not sure this initialization is strictly necessary either, but it also
> seems to be a common convention for this function, so either way.
> 
> Connie, does vfio_ccw_get_region() leak this?  It appears to call
> vfio_get_dev_region_info() and vfio_get_region_info() several times with
> the same pointer without freeing it between uses.
> 
> Thanks,
> Alex
> 
>> +    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)
>> +{
>> +    if (vbasedev->migration_blocker) {
>> +        migrate_del_blocker(vbasedev->migration_blocker);
>> +        error_free(vbasedev->migration_blocker);
>> +        vbasedev->migration_blocker = NULL;
>> +    }
>> +
>> +    vfio_migration_region_exit(vbasedev);
>> +    g_free(vbasedev->migration);
>> +}
>> diff --git a/hw/vfio/trace-events b/hw/vfio/trace-events
>> index a0c7b49a2ebc..8fe913175d85 100644
>> --- a/hw/vfio/trace-events
>> +++ b/hw/vfio/trace-events
>> @@ -145,3 +145,8 @@ 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 */
>