Messages in this thread | | | Subject | Re: [PATCH v8 09/10] vduse: Introduce VDUSE - vDPA Device in Userspace | From | Jason Wang <> | Date | Thu, 24 Jun 2021 11:34:46 +0800 |
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在 2021/6/23 下午1:50, Yongji Xie 写道: > On Wed, Jun 23, 2021 at 11:31 AM Jason Wang <jasowang@redhat.com> wrote: >> >> 在 2021/6/22 下午4:14, Yongji Xie 写道: >>> On Tue, Jun 22, 2021 at 3:50 PM Jason Wang <jasowang@redhat.com> wrote: >>>> 在 2021/6/22 下午3:22, Yongji Xie 写道: >>>>>> We need fix a way to propagate the error to the userspace. >>>>>> >>>>>> E.g if we want to stop the deivce, we will delay the status reset until >>>>>> we get respose from the userspace? >>>>>> >>>>> I didn't get how to delay the status reset. And should it be a DoS >>>>> that we want to fix if the userspace doesn't give a response forever? >>>> You're right. So let's make set_status() can fail first, then propagate >>>> its failure via VHOST_VDPA_SET_STATUS. >>>> >>> OK. So we only need to propagate the failure in the vhost-vdpa case, right? >> >> I think not, we need to deal with the reset for virtio as well: >> >> E.g in register_virtio_devices(), we have: >> >> /* We always start by resetting the device, in case a previous >> * driver messed it up. This also tests that code path a >> little. */ >> dev->config->reset(dev); >> >> We probably need to make reset can fail and then fail the >> register_virtio_device() as well. >> > OK, looks like virtio_add_status() and virtio_device_ready()[1] should > be also modified if we need to propagate the failure in the > virtio-vdpa case. Or do we only need to care about the reset case? > > [1] https://lore.kernel.org/lkml/20210517093428.670-1-xieyongji@bytedance.com/
My understanding is DRIVER_OK is not something that needs to be validated:
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DRIVER_OK (4) Indicates that the driver is set up and ready to drive the device.
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Since the spec doesn't require to re-read the and check if DRIVER_OK is set in 3.1.1 Driver Requirements: Device Initialization.
It's more about "telling the device that driver is ready."
But we don have some status bit that requires the synchronization with the device.
1) FEATURES_OK, spec requires to re-read the status bit to check whether or it it was set by the device:
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Re-read device status to ensure the FEATURES_OK bit is still set: otherwise, the device does not support our subset of features and the device is unusable.
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This is useful for some device which can only support a subset of the features. E.g a device that can only work for packed virtqueue. This means the current design of set_features won't work, we need either:
1a) relay the set_features request to userspace
or
1b) introduce a mandated_device_features during device creation and validate the driver features during the set_features(), and don't set FEATURES_OK if they don't match.
2) Some transports (PCI) requires to re-read the status to ensure the synchronization.
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After writing 0 to device_status, the driver MUST wait for a read of device_status to return 0 before reinitializing the device.
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So we need to deal with both FEATURES_OK and reset, but probably not DRIVER_OK.
Thanks
> > Thanks, > Yongji >
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