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Message-ID: <863668de-4ecb-34e0-aae6-207e4bea66cd@huawei.com>
Date:   Wed, 7 Dec 2022 08:24:23 +0800
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Subject: Re: [PATCH v2] vp_vdpa: harden the logic of set status
To:     Stefano Garzarella <sgarzare@redhat.com>
CC:     <stefanha@redhat.com>, <mst@redhat.com>, <jasowang@redhat.com>,
        <eperezma@redhat.com>, <cohuck@redhat.com>,
        <arei.gonglei@huawei.com>, <yechuan@huawei.com>,
        <huangzhichao@huawei.com>,
        <virtualization@lists.linux-foundation.org>,
        <linux-kernel@vger.kernel.org>
References: <20221206021321.2400-1-longpeng2@huawei.com>
 <20221206110040.q5i2k7ypojuira2e@sgarzare-redhat>
From:   "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)" 
        <longpeng2@huawei.com>
In-Reply-To: <20221206110040.q5i2k7ypojuira2e@sgarzare-redhat>
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在 2022/12/6 19:00, Stefano Garzarella 写道:
> On Tue, Dec 06, 2022 at 10:13:21AM +0800, Longpeng(Mike) wrote:
>> From: Longpeng <longpeng2@huawei.com>
>>
>> 1. We should not set status to 0 when invoking vp_vdpa_set_status(),
>>   trigger a warning in that case.
>>
>> 2. The driver MUST wait for a read of device_status to return 0 before
>>   reinitializing the device. But we also don't want to keep us in an
>>   infinite loop forever, so wait for 5s if we try to reset the device.
>>
>> Signed-off-by: Longpeng <longpeng2@huawei.com>
>> ---
>> Changes v1->v2:
>>  - use WARN_ON instead of BUG_ON. [Stefano]
>>  - use "warning + failed" instead of "infinite loop". [Jason, Stefano]
>>  - use usleep_range instead of msleep (checkpatch). [Longpeng]
>>
>> ---
>> drivers/vdpa/virtio_pci/vp_vdpa.c | 22 ++++++++++++++++++++++
>> 1 file changed, 22 insertions(+)
>>
>> diff --git a/drivers/vdpa/virtio_pci/vp_vdpa.c 
>> b/drivers/vdpa/virtio_pci/vp_vdpa.c
>> index 13701c2a1963..a2d3b13ac646 100644
>> --- a/drivers/vdpa/virtio_pci/vp_vdpa.c
>> +++ b/drivers/vdpa/virtio_pci/vp_vdpa.c
>> @@ -214,6 +214,9 @@ static void vp_vdpa_set_status(struct vdpa_device 
>> *vdpa, u8 status)
>>     struct virtio_pci_modern_device *mdev = vp_vdpa_to_mdev(vp_vdpa);
>>     u8 s = vp_vdpa_get_status(vdpa);
>>
>> +    /* We should never be setting status to 0. */
>> +    WARN_ON(status == 0);
>> +
>>     if (status & VIRTIO_CONFIG_S_DRIVER_OK &&
>>         !(s & VIRTIO_CONFIG_S_DRIVER_OK)) {
>>         vp_vdpa_request_irq(vp_vdpa);
>> @@ -222,14 +225,33 @@ static void vp_vdpa_set_status(struct 
>> vdpa_device *vdpa, u8 status)
>>     vp_modern_set_status(mdev, status);
>> }
>>
>> +#define VP_VDPA_RESET_TMOUT_MS 5000 /* 5s */
> 
> What about moving this define on top of this file?
> Near the other macro.
> 
> And I would use TIMEOUT entirely.
> 
Okay.

>> +
>> static int vp_vdpa_reset(struct vdpa_device *vdpa, bool clear)
>> {
>>     struct vp_vdpa *vp_vdpa = vdpa_to_vp(vdpa);
>>     struct virtio_pci_modern_device *mdev = vp_vdpa_to_mdev(vp_vdpa);
>>     u8 s = vp_vdpa_get_status(vdpa);
>> +    unsigned long timeout;
>>
>>     vp_modern_set_status(mdev, 0);
>>
>> +    /*
>> +     * As the virtio v1.1 spec (4.1.4.3.2) says: After writing 0 to
> 
> I think we can refer to the lates v1.2 (the section should be the same).
> 
Okay, will do in next version, thanks.

>> +     * device_status, the driver MUST wait for a read of device_status
>> +     * to return 0 before reinitializing the device.
>> +     * To avoid keep us here forever, we only wait for 5 seconds.
>> +     */
>> +    timeout = jiffies + msecs_to_jiffies(VP_VDPA_RESET_TMOUT_MS);
>> +    while (vp_modern_get_status(mdev)) {
>> +        usleep_range(1000, 1500);
>> +        if (time_after(jiffies, timeout)) {
>> +            dev_err(&mdev->pci_dev->dev,
>> +                "vp_vdpa: fail to reset device\n");
>> +            return -ETIMEDOUT;
>> +        }
>> +    }
>> +
>>     if (s & VIRTIO_CONFIG_S_DRIVER_OK)
>>         vp_vdpa_free_irq(vp_vdpa);
>>
>> -- 
>> 2.23.0
>>
> 
> The rest LGTM!
> 
> Thanks,
> Stefano
> 
> 
> .