From: olof@lixom•net (Olof Johansson)
To: Jake Moilanen <moilanen@austin•ibm.com>
Cc: linuxppc-dev@ozlabs•org, paulus@samba•org
Subject: Re: [PATCH] DMA 4GB boundary protection
Date: Thu, 22 Mar 2007 12:53:24 -0500 [thread overview]
Message-ID: <20070322175324.GA21120@lixom.net> (raw)
In-Reply-To: <1174511149.5225.135.camel@goblue>
On Wed, Mar 21, 2007 at 04:05:48PM -0500, Jake Moilanen wrote:
> @@ -480,6 +495,21 @@ struct iommu_table *iommu_init_table(str
> ppc_md.tce_free(tbl, tbl->it_offset, tbl->it_size);
> #endif
>
> + /*
> + * DMA cannot cross 4 GB boundary. Mark first entry of each 4
> + * GB chunk as reserved.
> + */
> + if (protect4gb) {
> + start_addr = tbl->it_offset << IOMMU_PAGE_SHIFT;
> + /* go up to next 4GB boundary */
> + start_addr = (start_addr + 0x00000000ffffffffl) >> 32;
> + end_addr = (tbl->it_offset + tbl->it_size) << IOMMU_PAGE_SHIFT;
> + for (index = start_addr; index < end_addr; index += (1l << 32)) {
> + /* Reserve 4GB entry */
> + __set_bit((index >> IOMMU_PAGE_SHIFT) - tbl->it_offset,
> tbl->it_map);
> + }
> + }
> +
This is done a bit more complicated than it has to be. The >> 32 is a
red flag as well.
I would also like it to be the last page in the range, not the first
(since otherwise you'll reserve even if the window is less than 4GB.
Something like (untested):
entries_per_4g = 0x100000000 >> IOMMU_PAGE_SHIFT;
/* Mark the last bit before a 4GB boundary as used */
start_index = tbl->it_offset | (entries_per_4g - 1);
end_index = tbl->it_offset + tbl->it_size;
for (index = start_index; index < end_index; index += entries_per_4g)
__set_bit(index, tbl->it_map);
Is easier to follow.
-Olof
next prev parent reply other threads:[~2007-03-22 17:39 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-02 21:49 [PATCH] DMA 4GB boundary protection Jake Moilanen
2007-03-02 22:27 ` Olof Johansson
2007-03-03 8:27 ` Benjamin Herrenschmidt
2007-03-03 23:25 ` Olof Johansson
2007-03-04 5:17 ` Christoph Hellwig
2007-03-04 5:52 ` Olof Johansson
2007-03-03 23:29 ` Olof Johansson
2007-03-03 23:32 ` Segher Boessenkool
2007-03-03 23:57 ` Olof Johansson
2007-03-21 21:05 ` Jake Moilanen
2007-03-21 21:39 ` Olof Johansson
2007-03-22 17:53 ` Olof Johansson [this message]
2007-03-22 17:47 ` Jake Moilanen
2007-03-22 22:52 ` Segher Boessenkool
2007-03-27 20:10 ` Jake Moilanen
2007-03-27 20:55 ` Benjamin Herrenschmidt
2007-03-27 23:48 ` Paul Mackerras
2007-03-28 15:56 ` Olof Johansson
2007-03-28 18:17 ` Jake Moilanen
2007-03-28 23:23 ` Benjamin Herrenschmidt
2007-03-29 13:44 ` Jake Moilanen
2007-03-29 14:52 ` Olof Johansson
2007-03-29 21:54 ` Benjamin Herrenschmidt
2007-04-23 12:22 ` Paul Mackerras
2007-04-24 3:07 ` Olof Johansson
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=20070322175324.GA21120@lixom.net \
--to=olof@lixom$(echo .)net \
--cc=linuxppc-dev@ozlabs$(echo .)org \
--cc=moilanen@austin$(echo .)ibm.com \
--cc=paulus@samba$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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