Re: How to resolve an issue in swiotlb environment?

shuah
2019-06-13T23:19:03Z

On 6/13/19 11:16 AM, Alan Stern wrote:
> On Thu, 13 Jun 2019, Christoph Hellwig wrote:
>
>> On Wed, Jun 12, 2019 at 10:43:11AM -0400, Alan Stern wrote:
>>> Would it be okay to rely on the assumption that USB block devices never
>>> have block size < 512? (We could even add code to the driver to
>>> enforce this, although refusing to handle such devices at all might be
>>> worse than getting an occasional error.)
>>
>> sd.c only supports a few specific sector size, and none of them is
>> < 512 bytes:
>>
>> if (sector_size != 512 &&
>> sector_size != 1024 &&
>> sector_size != 2048 &&
>> sector_size != 4096) {
>> ...
>> sdkp->capacity = 0;
>
> Great! So all we have to do is fix vhci-hcd. Then we can remove all
> the virt_boundary_mask stuff from usb-storage and uas entirely.
>
> (I'm assuming wireless USB isn't a genuine issue. As far as I know, it
> is pretty much abandoned at this point.)
>
> Valentina and Shua: Adding SG support to vhci-hcd shouldn't be too
> hard. It ought to be possible even without changing the network
> protocol.
>

I will start taking a look at this. Is there a target release in plan
to drop virt_boundary_mask stuff?

thanks,
-- Shuah