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SubjectRe: [RFC PATCH] virtio: make sure legacy pci device gain 32bit-pfn vq
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在 2021/12/8 下午7:08, Michael S. Tsirkin 写道:
[snip]
>>>>
>>>> Hi, Michael
>>>>
>>>> Thanks for the comment, unfortunately modify device is not an option for us
>>>> :-(
>>>>
>>>> Is there any idea on how to solve this issue properly?
>>>>
>>>> Regards,
>>>> Michael Wang
>>>
>>> By the way, there is a bug in the error message. Want to fix that?
>>
>> Could you please provide more detail about the bug? We'd like to help fixing
>> it :-)
>
> virtio-pci 0000:14:00.0: platform bug: legacy virtio-mmio must ...
>
> should be virtio-pci not virtio-mmio

Patch on the way~

>
>
>
>> Besides, I've checked that patch but it can't address our issue, we actually
>> have this legacy pci device on arm platform, and the memory layout is
>> unfriendly since allocation rarely providing page-address below 44bit, we
>> understand the virtio-iommu case should not do force dma, while we don't
>> have that so it's just working fine.
>>
>> Regards,
>> Michael Wang
>
> Hmm wait a sec is it a physical device or a hypervisor?
> If a physical one then doesn't it need VIRTIO_F_ORDER_PLATFORM
> on ARM?

The PCI device is virtual, I can't see how VIRTIO_F_ORDER_PLATFORM help
address this issue, legacy pci config is 32bit but it's 36, seems like
will never be included?

Regards,
Michael Wang

>
>
>
>>>
>>>
>>>>>
>>>>>> ---
>>>>>> drivers/virtio/virtio_pci_legacy.c | 10 ++++++++++
>>>>>> drivers/virtio/virtio_ring.c | 3 +++
>>>>>> include/linux/virtio.h | 1 +
>>>>>> 3 files changed, 14 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/virtio/virtio_pci_legacy.c
>>>>>> b/drivers/virtio/virtio_pci_legacy.c
>>>>>> index d62e983..11f2ebf 100644
>>>>>> --- a/drivers/virtio/virtio_pci_legacy.c
>>>>>> +++ b/drivers/virtio/virtio_pci_legacy.c
>>>>>> @@ -263,6 +263,16 @@ int virtio_pci_legacy_probe(struct virtio_pci_device
>>>>>> *vp_dev)
>>>>>> vp_dev->setup_vq = setup_vq;
>>>>>> vp_dev->del_vq = del_vq;
>>>>>>
>>>>>> + /*
>>>>>> + * The legacy pci device requre 32bit-pfn vq,
>>>>>> + * or setup_vq() will failed.
>>>>>> + *
>>>>>> + * Thus we make sure vring_use_dma_api() will
>>>>>> + * return true during the allocation by marking
>>>>>> + * force_dma here.
>>>>>> + */
>>>>>> + vp_dev->vdev.force_dma = true;
>>>>>> +
>>>>>> return 0;
>>>>>>
>>>>>> err_iomap:
>>>>>> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
>>>>>> index 3035bb6..6562e01 100644
>>>>>> --- a/drivers/virtio/virtio_ring.c
>>>>>> +++ b/drivers/virtio/virtio_ring.c
>>>>>> @@ -245,6 +245,9 @@ static inline bool virtqueue_use_indirect(struct
>>>>>> virtqueue *_vq,
>>>>>>
>>>>>> static bool vring_use_dma_api(struct virtio_device *vdev)
>>>>>> {
>>>>>> + if (vdev->force_dma)
>>>>>> + return true;
>>>>>> +
>>>>>> if (!virtio_has_dma_quirk(vdev))
>>>>>> return true;
>>>>>>
>>>>>> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
>>>>>> index 41edbc0..a4eb29d 100644
>>>>>> --- a/include/linux/virtio.h
>>>>>> +++ b/include/linux/virtio.h
>>>>>> @@ -109,6 +109,7 @@ struct virtio_device {
>>>>>> bool failed;
>>>>>> bool config_enabled;
>>>>>> bool config_change_pending;
>>>>>> + bool force_dma;
>>>>>> spinlock_t config_lock;
>>>>>> spinlock_t vqs_list_lock; /* Protects VQs list access */
>>>>>> struct device dev;
>>>>>> --
>>>>>> 1.8.3.1

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