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

[Alex Williamson <alex.williamson@redhat.com>]

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,

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 */  
> >   
>