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Subject: Re: [RFC v2 1/4] hisi-acc-vfio-pci: add new vfio_pci driver for
 HiSilicon ACC devices
To:     Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
        "Leon Romanovsky" <leon@kernel.org>
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        yuzenghui <yuzenghui@huawei.com>,
        Jonathan Cameron <jonathan.cameron@huawei.com>,
        "Wangzhou (B)" <wangzhou1@hisilicon.com>
References: <20210702095849.1610-1-shameerali.kolothum.thodi@huawei.com>
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From:   Max Gurtovoy <mgurtovoy@nvidia.com>
Message-ID: <d02dff3a-8035-ced1-7fc3-fcff791f9203@nvidia.com>
Date:   Mon, 5 Jul 2021 12:41:30 +0300
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On 7/5/2021 11:47 AM, Shameerali Kolothum Thodi wrote:
>
>> -----Original Message-----
>> From: Leon Romanovsky [mailto:leon@kernel.org]
>> Sent: 04 July 2021 08:04
>> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
>> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org;
>> linux-crypto@vger.kernel.org; alex.williamson@redhat.com; jgg@nvidia.com;
>> mgurtovoy@nvidia.com; Linuxarm <linuxarm@huawei.com>; liulongfang
>> <liulongfang@huawei.com>; Zengtao (B) <prime.zeng@hisilicon.com>;
>> yuzenghui <yuzenghui@huawei.com>; Jonathan Cameron
>> <jonathan.cameron@huawei.com>; Wangzhou (B) <wangzhou1@hisilicon.com>
>> Subject: Re: [RFC v2 1/4] hisi-acc-vfio-pci: add new vfio_pci driver for HiSilicon
>> ACC devices
>>
>> On Fri, Jul 02, 2021 at 10:58:46AM +0100, Shameer Kolothum wrote:
>>> Add a vendor-specific vfio_pci driver for HiSilicon ACC devices.
>>> This will be extended in follow-up patches to add support for
>>> vfio live migration feature.
>>>
>>> Signed-off-by: Shameer Kolothum
>> <shameerali.kolothum.thodi@huawei.com>
>>> ---
>>>   drivers/vfio/pci/Kconfig             |   9 +++
>>>   drivers/vfio/pci/Makefile            |   2 +
>>>   drivers/vfio/pci/hisi_acc_vfio_pci.c | 100 +++++++++++++++++++++++++++
>>>   3 files changed, 111 insertions(+)
>>>   create mode 100644 drivers/vfio/pci/hisi_acc_vfio_pci.c
>> <...>
>>
>>> +static const struct vfio_device_ops hisi_acc_vfio_pci_ops = {
>>> +	.name		= "hisi-acc-vfio-pci",
>>> +	.open		= hisi_acc_vfio_pci_open,
>>> +	.release	= vfio_pci_core_release,
>>> +	.ioctl		= vfio_pci_core_ioctl,
>>> +	.read		= vfio_pci_core_read,
>>> +	.write		= vfio_pci_core_write,
>>> +	.mmap		= vfio_pci_core_mmap,
>>> +	.request	= vfio_pci_core_request,
>>> +	.match		= vfio_pci_core_match,
>>> +	.reflck_attach	= vfio_pci_core_reflck_attach,
>> I don't remember what was proposed in vfio-pci-core conversion patches,
>> but would expect that default behaviour is to fallback to vfio_pci_core_* API
>> if ".release/.ioctl/e.t.c" are not redefined.
> Yes, that would be nice, but don't think it does that in latest(v4).
>
> Hi Max,
> Could we please consider fall back to the core defaults, may be check and assign defaults
> in vfio_pci_core_register_device() ?

I don't see why we should do this.

vfio_pci_core.ko is just a library driver. It shouldn't decide for the 
vendor driver ops.

If a vendor driver would like to use its helper functions - great.

If it wants to override it - great.

If it wants to leave some op as NULL - it can do it also.


>
> Thanks,
> Shameer