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

["Cédric Le Goater" <clg@redhat.com>]

On 10/18/23 04:41, Duan, Zhenzhong wrote:
> 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.

I see the idea was challenged, not rejected. I need to dig in further and this
will take time.

Thanks,

C.