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]

Message-ID: <1268101514.22204.137.camel@pasglop>
Date:	Tue, 09 Mar 2010 13:25:14 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Pavel Machek <pavel@....cz>,
	Catalin Marinas <catalin.marinas@....com>,
	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>,
	mdharm-kernel@...-eyed-alien.net, linux-usb@...r.kernel.org,
	x0082077@...com, sshtylyov@...mvista.com, tom.leiming@...il.com,
	bigeasy@...utronix.de, oliver@...kum.org,
	linux-kernel@...r.kernel.org, santosh.shilimkar@...com,
	greg@...ah.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: USB mass storage and ARM cache coherency

On Sun, 2010-03-07 at 09:07 +0530, James Bottomley wrote:
> So, assuming full congruence of user space, can't you use the VMA as an
> indicator?  i.e. if we have no user space mappings, we have to flush the
> icache ... if we have one or more, the icache has been flushed and
> placing the same page congruently in a different address space benefits
> from that prior flush, so consequently there's no need to flush again?

the VMA ? Or you mean struct page -> mapping ? That would work I suppose
in the case where we want to flush the icache pages for all pages mapped
into user space. But on processors that support per-page execute
permission, we really only want to flush pages that are executed from
(lazily). In that case, we do need a dedicated bit to keep track of
whether a given page has been flushed already.

> I also think we've established the relevant facts for the I/O thread
> (that we only need to either flush the kernel D cache or mark it as to
> be flushed later on PIO reads).  We're now into deep technicalities of
> how the mm system operates at the architecture level, so perhaps we
> should move this to linux-arch? 

No objection though moving threads after the fact is a recipe for
trouble :-)

Cheers,
Ben.


--
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/