From: Alan Stern <stern@rowland.harvard.edu>
To: Christoph Hellwig <hch@lst.de>
Cc: Oliver Neukum <oneukum@suse.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: Re: How to resolve an issue in swiotlb environment?
Date: Wed, 12 Jun 2019 10:43:11 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1906121038210.1557-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <20190612120653.GA25285@lst.de>
On Wed, 12 Jun 2019, Christoph Hellwig wrote:
> On Wed, Jun 12, 2019 at 01:46:06PM +0200, Oliver Neukum wrote:
> > > Thay is someething the virt_boundary prevents. But could still give
> > > you something like:
> > >
> > > 1536 4096 4096 1024
> > >
> > > or
> > > 1536 16384 8192 4096 16384 512
> >
> > That would kill the driver, if maxpacket were 1024.
> >
> > USB has really two kinds of requirements
> >
> > 1. What comes from the protocol
> > 2. What comes from the HCD
> >
> > The protocol wants just multiples of maxpacket. XHCI can satisfy
> > that in arbitrary scatter/gather. Other HCs cannot.
>
> We have no real way to enforce that for the other HCs unfortunately.
> I can't really think of any better way to handle their limitations
> except for setting max_segments to 1 or bounce buffering.
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.)
As I mentioned before, the only HCD that sometimes ends up with
maxpacket = 1024 but is unable to do full SG is vhci-hcd, and that one
shouldn't be too hard to fix.
Alan Stern
next prev parent reply other threads:[~2019-06-12 14:44 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-03 6:42 How to resolve an issue in swiotlb environment? Yoshihiro Shimoda
2019-06-07 12:00 ` Yoshihiro Shimoda
2019-06-10 7:31 ` Biju Das
2019-06-10 11:13 ` Yoshihiro Shimoda
2019-06-10 12:32 ` Christoph Hellwig
2019-06-10 18:46 ` Alan Stern
2019-06-11 6:41 ` Christoph Hellwig
2019-06-11 14:51 ` Alan Stern
2019-06-12 7:30 ` Christoph Hellwig
2019-06-12 8:52 ` Yoshihiro Shimoda
2019-06-12 11:31 ` Christoph Hellwig
2019-06-13 4:52 ` Yoshihiro Shimoda
2019-06-12 11:46 ` Oliver Neukum
2019-06-12 12:06 ` Christoph Hellwig
2019-06-12 14:43 ` Alan Stern [this message]
2019-06-13 7:39 ` Christoph Hellwig
2019-06-13 16:57 ` Martin K. Petersen
2019-06-13 17:16 ` Alan Stern
2019-06-13 18:18 ` Greg KH
2019-06-13 23:01 ` shuah
2019-06-14 14:44 ` Alan Stern
2019-06-18 15:28 ` shuah
2019-06-19 20:23 ` shuah
2019-06-19 21:05 ` Alan Stern
2019-06-21 17:43 ` Suwan Kim
2019-06-11 6:49 ` Yoshihiro Shimoda
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=Pine.LNX.4.44L0.1906121038210.1557-100000@iolanthe.rowland.org \
--to=stern@rowland.harvard.edu \
--cc=hch@lst.de \
--cc=iommu@lists.linux-foundation.org \
--cc=linux-block@vger.kernel.org \
--cc=linux-renesas-soc@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=oneukum@suse.com \
--cc=yoshihiro.shimoda.uh@renesas.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).