netdev - Re: [PATCH v10 04/17] vdpa: Fail the vdpa_reset() if fail to set device status to zero

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Date:   Wed, 4 Aug 2021 16:30:47 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Yongji Xie <xieyongji@...edance.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Stefano Garzarella <sgarzare@...hat.com>,
        Parav Pandit <parav@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Christian Brauner <christian.brauner@...onical.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, bcrl@...ck.org,
        Jonathan Corbet <corbet@....net>,
        Mika Penttilä <mika.penttila@...tfour.com>,
        Dan Carpenter <dan.carpenter@...cle.com>, joro@...tes.org,
        Greg KH <gregkh@...uxfoundation.org>,
        He Zhe <zhe.he@...driver.com>,
        Liu Xiaodong <xiaodong.liu@...el.com>,
        Joe Perches <joe@...ches.com>, songmuchun@...edance.com,
        virtualization <virtualization@...ts.linux-foundation.org>,
        netdev@...r.kernel.org, kvm <kvm@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v10 04/17] vdpa: Fail the vdpa_reset() if fail to set
 device status to zero


在 2021/8/3 下午5:31, Yongji Xie 写道:
> On Tue, Aug 3, 2021 at 3:58 PM Jason Wang <jasowang@...hat.com> wrote:
>>
>> 在 2021/7/29 下午3:34, Xie Yongji 写道:
>>> Re-read the device status to ensure it's set to zero during
>>> resetting. Otherwise, fail the vdpa_reset() after timeout.
>>>
>>> Signed-off-by: Xie Yongji <xieyongji@...edance.com>
>>> ---
>>>    include/linux/vdpa.h | 15 ++++++++++++++-
>>>    1 file changed, 14 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
>>> index 406d53a606ac..d1a80ef05089 100644
>>> --- a/include/linux/vdpa.h
>>> +++ b/include/linux/vdpa.h
>>> @@ -6,6 +6,7 @@
>>>    #include <linux/device.h>
>>>    #include <linux/interrupt.h>
>>>    #include <linux/vhost_iotlb.h>
>>> +#include <linux/delay.h>
>>>
>>>    /**
>>>     * struct vdpa_calllback - vDPA callback definition.
>>> @@ -340,12 +341,24 @@ static inline struct device *vdpa_get_dma_dev(struct vdpa_device *vdev)
>>>        return vdev->dma_dev;
>>>    }
>>>
>>> -static inline void vdpa_reset(struct vdpa_device *vdev)
>>> +#define VDPA_RESET_TIMEOUT_MS 1000
>>> +
>>> +static inline int vdpa_reset(struct vdpa_device *vdev)
>>>    {
>>>        const struct vdpa_config_ops *ops = vdev->config;
>>> +     int timeout = 0;
>>>
>>>        vdev->features_valid = false;
>>>        ops->set_status(vdev, 0);
>>> +     while (ops->get_status(vdev)) {
>>> +             timeout += 20;
>>> +             if (timeout > VDPA_RESET_TIMEOUT_MS)
>>> +                     return -EIO;
>>> +
>>> +             msleep(20);
>>> +     }
>>
>> I wonder if it's better to do this in the vDPA parent?
>>
>> Thanks
>>
> Sorry, I didn't get you here. Do you mean vDPA parent driver (e.g.
> VDUSE)?


Yes, since the how it's expected to behave depends on the specific hardware.

Even for the spec, the behavior is transport specific:

PCI: requires reread until 0
MMIO: doesn't require but it might not work for the hardware so we 
decide to change
CCW: the succeed of the ccw command means the success of the reset

Thanks


> Actually I didn't find any other place where I can do
> set_status() and get_status().
>
> Thanks,
> Yongji
>