linux-kernel - Re: USB mass storage and ARM cache coherency

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 02 Feb 2010 14:34:14 +0000
From:	Catalin Marinas <catalin.marinas@....com>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Matthew Dharm <mdharm-kernel@...-eyed-alien.net>,
	Sergei Shtylyov <sshtylyov@...mvista.com>,
	Ming Lei <tom.leiming@...il.com>, linux-usb@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Sebastian Siewior <bigeasy@...utronix.de>,
	Greg KH <greg@...ah.com>
Subject: Re: USB mass storage and ARM cache coherency

On Tue, 2010-02-02 at 13:08 +0000, Oliver Neukum wrote:
> Am Dienstag, 2. Februar 2010 13:39:35 schrieb Catalin Marinas:
> > > For storage that is correct. But what about other sources of pages,
> > > for example iSCSI?
> >
> > In the iSCSI case, does the HCD driver write directly to a page cache
> > page? Or it just fills in network packets that are copied to page cache
> > pages by the iSCSI code (sorry, I'm not familiar with this part of the
> > kernel). If the latter, the cache flushing in the HCD driver would not
> > help and it needs to be done in the iSCSI code.
> 
> As far as I can tell iSCSI does a private copy. But I don't know how
> many methods to transfer code pages over USB exist. I'd say the
> conservative solution is to flush for everything but control transfers.

flush_dcache_page() is on many architectures implemented lazily so that
if the page isn't mapped in user space no flushing takes place. It's
mainly the cost of virt_to_page() which I suspect is slightly higher
with sparsemem enabled.

-- 
Catalin

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/