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

From: Alex Williamson <alex.williamson@redhat.com>
To: Kirti Wankhede <kwankhede@nvidia.com>
Cc: cohuck@redhat.com, cjia@nvidia.com, aik@ozlabs.ru,
	Zhengxiao.zx@Alibaba-inc.com, shuangtai.tst@alibaba-inc.com,
	qemu-devel@nongnu.org, peterx@redhat.com, eauger@redhat.com,
	yi.l.liu@intel.com, quintela@redhat.com, ziye.yang@intel.com,
	armbru@redhat.com, mlevitsk@redhat.com, pasic@linux.ibm.com,
	felipe@nutanix.com, zhi.a.wang@intel.com, kevin.tian@intel.com,
	yan.y.zhao@intel.com, dgilbert@redhat.com,
	changpeng.liu@intel.com, eskultet@redhat.com, Ken.Xue@amd.com,
	jonathan.davies@nutanix.com, pbonzini@redhat.com
Subject: Re: [PATCH v26 04/17] vfio: Add migration region initialization and finalize function
Date: Fri, 25 Sep 2020 14:20:06 -0600	[thread overview]
Message-ID: <20200925142006.2b62f856@x1.home> (raw)
In-Reply-To: <1600817059-26721-5-git-send-email-kwankhede@nvidia.com>

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().

> +
> +    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 */