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Subject: Re: [RFC PATCH 2/4] mdev: introduce helper to set per device dma ops
To:     Alex Williamson <alex.williamson@redhat.com>
Cc:     mst@redhat.com, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, kwankhede@nvidia.com,
        cohuck@redhat.com, tiwei.bie@intel.com, maxime.coquelin@redhat.com,
        cunming.liang@intel.com, zhihong.wang@intel.com,
        rob.miller@broadcom.com, idos@mellanox.com, xiao.w.wang@intel.com,
        haotian.wang@sifive.com
References: <20190910081935.30516-1-jasowang@redhat.com>
 <20190910081935.30516-3-jasowang@redhat.com>
 <20190917130044.4fb97637@x1.home>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <f0df968e-9322-829a-11c7-ca62408b9bae@redhat.com>
Date:   Wed, 18 Sep 2019 13:58:42 +0800
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On 2019/9/18 上午3:00, Alex Williamson wrote:
> On Tue, 10 Sep 2019 16:19:33 +0800
> Jason Wang<jasowang@redhat.com>  wrote:
>
>> This patch introduces mdev_set_dma_ops() which allows parent to set
>> per device DMA ops. This help for the kernel driver to setup a correct
>> DMA mappings.
>>
>> Signed-off-by: Jason Wang<jasowang@redhat.com>
>> ---
>>   drivers/vfio/mdev/mdev_core.c | 7 +++++++
>>   include/linux/mdev.h          | 2 ++
>>   2 files changed, 9 insertions(+)
>>
>> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
>> index b558d4cfd082..eb28552082d7 100644
>> --- a/drivers/vfio/mdev/mdev_core.c
>> +++ b/drivers/vfio/mdev/mdev_core.c
>> @@ -13,6 +13,7 @@
>>   #include <linux/uuid.h>
>>   #include <linux/sysfs.h>
>>   #include <linux/mdev.h>
>> +#include <linux/dma-mapping.h>
>>   
>>   #include "mdev_private.h"
>>   
>> @@ -27,6 +28,12 @@ static struct class_compat *mdev_bus_compat_class;
>>   static LIST_HEAD(mdev_list);
>>   static DEFINE_MUTEX(mdev_list_lock);
>>   
>> +void mdev_set_dma_ops(struct mdev_device *mdev, struct dma_map_ops *ops)
>> +{
>> +	set_dma_ops(&mdev->dev, ops);
>> +}
>> +EXPORT_SYMBOL(mdev_set_dma_ops);
>> +
> Why does mdev need to be involved here?  Your sample driver in 4/4 calls
> this from its create callback, where it could just as easily call:
>
>    set_dma_ops(mdev_dev(mdev), ops);
>
> Thanks,
> Alex


Yes, let me withdraw this patch.

Thanks