Re: How to resolve an issue in swiotlb environment?

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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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