linux-kernel - Re: [PATCH v1] virtio-pci: Fix legacy device flag setting error in probe

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Date:   Tue, 25 Jul 2023 00:18:23 -0400
From:   Feng Liu <feliu@...dia.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Bodong Wang <bodong@...dia.com>,
        Parav Pandit <parav@...dia.com>, Jiri Pirko <jiri@...dia.com>,
        Yishai Hadas <yishaih@...dia.com>
Subject: Re: [PATCH v1] virtio-pci: Fix legacy device flag setting error in
 probe



On 2023-07-24 p.m.11:41, Jason Wang wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Mon, Jul 24, 2023 at 9:14 PM Feng Liu <feliu@...dia.com> wrote:
>>
>>
>>
>> On 2023-07-20 p.m.1:14, Michael S. Tsirkin wrote:
>>> External email: Use caution opening links or attachments
>>>
>>>
>>> On Thu, Jul 20, 2023 at 10:27:04AM +0800, Jason Wang wrote:
>>>> On Wed, Jul 19, 2023 at 11:46 PM Feng Liu <feliu@...dia.com> wrote:
>>>>>
>>>>> The 'is_legacy' flag is used to differentiate between legacy vs modern
>>>>> device. Currently, it is based on the value of vp_dev->ldev.ioaddr.
>>>>> However, due to the shared memory of the union between struct
>>>>> virtio_pci_legacy_device and struct virtio_pci_modern_device, when
>>>>> virtio_pci_modern_probe modifies the content of struct
>>>>> virtio_pci_modern_device, it affects the content of struct
>>>>> virtio_pci_legacy_device, and ldev.ioaddr is no longer zero, causing
>>>>> the 'is_legacy' flag to be set as true. To resolve issue, when legacy
>>>>> device is probed, mark 'is_legacy' as true, when modern device is
>>>>> probed, keep 'is_legacy' as false.
>>>>>
>>>>> Fixes: 4f0fc22534e3 ("virtio_pci: Optimize virtio_pci_device structure size")
>>>>> Signed-off-by: Feng Liu <feliu@...dia.com>
>>>>> Reviewed-by: Parav Pandit <parav@...dia.com>
>>>>> Reviewed-by: Jiri Pirko <jiri@...dia.com>
>>>>> ---
>>>>>    drivers/virtio/virtio_pci_common.c | 2 --
>>>>>    drivers/virtio/virtio_pci_legacy.c | 1 +
>>>>>    2 files changed, 1 insertion(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
>>>>> index a6c86f916dbd..c2524a7207cf 100644
>>>>> --- a/drivers/virtio/virtio_pci_common.c
>>>>> +++ b/drivers/virtio/virtio_pci_common.c
>>>>> @@ -557,8 +557,6 @@ static int virtio_pci_probe(struct pci_dev *pci_dev,
>>>>>
>>>>>           pci_set_master(pci_dev);
>>>>>
>>>>> -       vp_dev->is_legacy = vp_dev->ldev.ioaddr ? true : false;
>>>>> -
>>>>>           rc = register_virtio_device(&vp_dev->vdev);
>>>>>           reg_dev = vp_dev;
>>>>>           if (rc)
>>>>> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
>>>>> index 2257f1b3d8ae..d9cbb02b35a1 100644
>>>>> --- a/drivers/virtio/virtio_pci_legacy.c
>>>>> +++ b/drivers/virtio/virtio_pci_legacy.c
>>>>> @@ -223,6 +223,7 @@ int virtio_pci_legacy_probe(struct virtio_pci_device *vp_dev)
>>>>>           vp_dev->config_vector = vp_config_vector;
>>>>>           vp_dev->setup_vq = setup_vq;
>>>>>           vp_dev->del_vq = del_vq;
>>>>> +       vp_dev->is_legacy = true;
>>>>
>>>> This seems break force_legacy for modern device:
>>>>
>>>>           if (force_legacy) {
>>>>                   rc = virtio_pci_legacy_probe(vp_dev);
>>>>                   /* Also try modern mode if we can't map BAR0 (no IO space). */
>>>>                   if (rc == -ENODEV || rc == -ENOMEM)
>>>>                           rc = virtio_pci_modern_probe(vp_dev);
>>>>
>>>> Thanks
>>>
>>> don't see the breakage here - can you explain a bit more?
>>>
>> Hi, Jason
>>
>> I also think there is no breakage herea and gave an explanation in
>> another email, please have a see.
> 
> I think I've made a mistake, the patch should be fine.
> 
>>
>> So are there any comments about this bug fix patch? Can this patch pass
>> the review?
> 
> Yes.
> 
> Acked-by: Jason Wang <jasowang@...hat.com>
> 
> Thanks
> 

Thanks Jason

>>
>> Thanks
>> Feng
>>
>>>>>
>>>>>           return 0;
>>>>>    }
>>>>> --
>>>>> 2.37.1 (Apple Git-137.1)
>>>>>
>>>
>>
>