How to resolve an issue in swiotlb environment?

shuah shuah at kernel.org
Thu Jun 13 23:01:05 UTC 2019


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



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