linux-kernel - Re: [RFC PATCH 2/4] mdev: introduce helper to set per device dma ops

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Message-ID: <f0df968e-9322-829a-11c7-ca62408b9bae@redhat.com>
Date:   Wed, 18 Sep 2019 13:58:42 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Alex Williamson <alex.williamson@...hat.com>
Cc:     mst@...hat.com, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kwankhede@...dia.com,
        cohuck@...hat.com, tiwei.bie@...el.com, maxime.coquelin@...hat.com,
        cunming.liang@...el.com, zhihong.wang@...el.com,
        rob.miller@...adcom.com, idos@...lanox.com, xiao.w.wang@...el.com,
        haotian.wang@...ive.com
Subject: Re: [RFC PATCH 2/4] mdev: introduce helper to set per device dma ops


On 2019/9/18 上午3:00, Alex Williamson wrote:
> On Tue, 10 Sep 2019 16:19:33 +0800
> Jason Wang<jasowang@...hat.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@...hat.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