RE: [PATCH v2 02/27] vfio: Introduce base object for VFIOContainer and targetted interface

[Duan, Zhenzhong]

Hi Cédric,

>-----Original Message-----
>From: Cédric Le Goater <clg@redhat.com>
>Sent: Tuesday, October 17, 2023 11:51 PM
>Subject: Re: [PATCH v2 02/27] vfio: Introduce base object for VFIOContainer and
>targetted interface
>
>On 10/16/23 10:31, Zhenzhong Duan wrote:
>> From: Eric Auger <eric.auger@redhat.com>
>>
>> Introduce a dumb VFIOContainer base object and its targetted interface.
>> This is willingly not a QOM object because we don't want it to be
>> visible from the user interface.  The VFIOContainer will be smoothly
>> populated in subsequent patches as well as interfaces.
>>
>> No fucntional change intended.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> Signed-off-by: Yi Liu <yi.l.liu@intel.com>
>> Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
>> ---
>>   include/hw/vfio/vfio-common.h         |  8 +--
>>   include/hw/vfio/vfio-container-base.h | 82 +++++++++++++++++++++++++++
>>   2 files changed, 84 insertions(+), 6 deletions(-)
>>   create mode 100644 include/hw/vfio/vfio-container-base.h
>>
>> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
>> index 34648e518e..9651cf921c 100644
>> --- a/include/hw/vfio/vfio-common.h
>> +++ b/include/hw/vfio/vfio-common.h
>> @@ -30,6 +30,7 @@
>>   #include <linux/vfio.h>
>>   #endif
>>   #include "sysemu/sysemu.h"
>> +#include "hw/vfio/vfio-container-base.h"
>>
>>   #define VFIO_MSG_PREFIX "vfio %s: "
>>
>> @@ -81,6 +82,7 @@ typedef struct VFIOAddressSpace {
>>   struct VFIOGroup;
>>
>>   typedef struct VFIOLegacyContainer {
>> +    VFIOContainer bcontainer;
>
>That's the parent class, right ?

Right.

>
>>       VFIOAddressSpace *space;
>>       int fd; /* /dev/vfio/vfio, empowered by the attached groups */
>>       MemoryListener listener;
>> @@ -200,12 +202,6 @@ typedef struct VFIODisplay {
>>       } dmabuf;
>>   } VFIODisplay;
>>
>> -typedef struct {
>> -    unsigned long *bitmap;
>> -    hwaddr size;
>> -    hwaddr pages;
>> -} VFIOBitmap;
>> -
>>   void vfio_host_win_add(VFIOLegacyContainer *container,
>>                          hwaddr min_iova, hwaddr max_iova,
>>                          uint64_t iova_pgsizes);
>> diff --git a/include/hw/vfio/vfio-container-base.h b/include/hw/vfio/vfio-
>container-base.h
>> new file mode 100644
>> index 0000000000..afc8543d22
>> --- /dev/null
>> +++ b/include/hw/vfio/vfio-container-base.h
>> @@ -0,0 +1,82 @@
>> +/*
>> + * VFIO BASE CONTAINER
>> + *
>> + * Copyright (C) 2023 Intel Corporation.
>> + * Copyright Red Hat, Inc. 2023
>> + *
>> + * Authors: Yi Liu <yi.l.liu@intel.com>
>> + *          Eric Auger <eric.auger@redhat.com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation; either version 2 of the License, or
>> + * (at your option) any later version.
>> +
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> +
>> + * You should have received a copy of the GNU General Public License along
>> + * with this program; if not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#ifndef HW_VFIO_VFIO_BASE_CONTAINER_H
>> +#define HW_VFIO_VFIO_BASE_CONTAINER_H
>> +
>> +#include "exec/memory.h"
>> +#ifndef CONFIG_USER_ONLY
>> +#include "exec/hwaddr.h"
>> +#endif
>> +
>> +typedef struct VFIOContainer VFIOContainer;
>> +typedef struct VFIODevice VFIODevice;
>> +typedef struct VFIOIOMMUBackendOpsClass VFIOIOMMUBackendOpsClass;
>> +
>> +typedef struct {
>> +    unsigned long *bitmap;
>> +    hwaddr size;
>> +    hwaddr pages;
>> +} VFIOBitmap;
>> +
>> +/*
>> + * This is the base object for vfio container backends
>> + */
>> +struct VFIOContainer {
>> +    VFIOIOMMUBackendOpsClass *ops;
>
>This is unexpected.
>
>I thought that an abstract QOM model for VFIOContainer was going
>to be introduced with a VFIOContainerClass with the ops below
>(VFIOIOMMUBackendOpsClass).
>
>Then, we would call :
>
>    VFIOContainerClass *vcc = VFIO_CONTAINER_GET_CLASS(container);
>
>to get the specific implementation for the current container.
>
>I don't understand the VFIOIOMMUBackendOpsClass pointer and
>TYPE_VFIO_IOMMU_BACKEND_OPS. It seems redundant.

The original implementation was abstract QOM model. But it wasn't accepted,
see https://lore.kernel.org/all/YmuFv2s5TPuw7K%2Fu@yekko/ for details.

Thanks
Zhenzhong