Hi,

On 11/28/20 4:48 PM, Tom Yan wrote:
> Apparently the former (with the chosen dma_dev) may cause problem in certain
> case (e.g. where thunderbolt dock and intel iommu are involved). The error
> observed was:
> 
> XHCI swiotlb buffer is full / DMAR: Device bounce map failed
> 
> For now we retain the clamp for hw_max_sectors against the 
> dma_max_mapping_size.
> Since the device/size for the clamp that is applied when the scsi request 
> queue
> is initialized/allocated is different than the one used here, we invalidate 
> the
> early clamping by making a fallback blk_queue_max_hw_sectors() call.
> 
> Signed-off-by: Tom Yan <tom.t...@gmail.com>

I can confirm that this fixes the network performance on a Lenovo Thunderbolt
dock generation 2, which uses an USB attach NIC.

With this patch added on top of 5.10-rc5 scp performance to another machine
on the local gbit LAN goes back from the regressed 1 MB/s to its original 
100MB/s
as it should be:

Tested-by: Hans de Goede <hdego...@redhat.com>

Regards,

Hans


> ---
>  drivers/usb/storage/uas.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/storage/uas.c b/drivers/usb/storage/uas.c
> index c8a577309e8f..5db1325cea20 100644
> --- a/drivers/usb/storage/uas.c
> +++ b/drivers/usb/storage/uas.c
> @@ -843,18 +843,21 @@ static int uas_slave_alloc(struct scsi_device *sdev)
>  static int uas_slave_configure(struct scsi_device *sdev)
>  {
>       struct uas_dev_info *devinfo = sdev->hostdata;
> -     struct device *dev = sdev->host->dma_dev;
> +     struct usb_device *udev = devinfo->udev;
>  
>       if (devinfo->flags & US_FL_MAX_SECTORS_64)
>               blk_queue_max_hw_sectors(sdev->request_queue, 64);
>       else if (devinfo->flags & US_FL_MAX_SECTORS_240)
>               blk_queue_max_hw_sectors(sdev->request_queue, 240);
> -     else if (devinfo->udev->speed >= USB_SPEED_SUPER)
> +     else if (udev->speed >= USB_SPEED_SUPER)
>               blk_queue_max_hw_sectors(sdev->request_queue, 2048);
> +     else
> +             blk_queue_max_hw_sectors(sdev->request_queue,
> +                                      SCSI_DEFAULT_MAX_SECTORS);
>  
>       blk_queue_max_hw_sectors(sdev->request_queue,
>               min_t(size_t, queue_max_hw_sectors(sdev->request_queue),
> -                   dma_max_mapping_size(dev) >> SECTOR_SHIFT));
> +                   dma_max_mapping_size(udev->bus->sysdev) >> SECTOR_SHIFT));
>  
>       if (devinfo->flags & US_FL_NO_REPORT_OPCODES)
>               sdev->no_report_opcodes = 1;
> @@ -1040,7 +1043,7 @@ static int uas_probe(struct usb_interface *intf, const 
> struct usb_device_id *id)
>       shost->can_queue = devinfo->qdepth - 2;
>  
>       usb_set_intfdata(intf, shost);
> -     result = scsi_add_host_with_dma(shost, &intf->dev, udev->bus->sysdev);
> +     result = scsi_add_host(shost, &intf->dev);
>       if (result)
>               goto free_streams;
>  
> 

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