From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Date: Tue, 22 Feb 2005 10:03:09 +0000 Subject: Re: [patch -mm series] ia64 specific /dev/mem handlers Message-Id: <20050222020309.4289504c.akpm@osdl.org> List-Id: References: <16923.193.128608.607599@jaguar.mkp.net> In-Reply-To: <16923.193.128608.607599@jaguar.mkp.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jes Sorensen Cc: linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org jes@trained-monkey.org (Jes Sorensen) wrote: > > Hi, > > This patch introduces ia64 specific read/write handlers for /dev/mem > access which is needed to avoid uncached pages to be accessed through > the cached kernel window which can lead to random corruption. It also > introduces a new page-flag PG_uncached which will be used to mark the > uncached pages. I assume this may be useful to other architectures as > well where the CPU may use speculative reads which conflict with > uncached access. In addition I moved do_write_mem to be under > ARCH_HAS_DEV_MEM as it's only ever used if that is defined. > > The patch is needed for the new ia64 special memory driver (mspec - > former fetchop). > > Patch is relative to 2.6.11-rc3-mm2 and relies on the ARCH_HAS_DEV_MEM > flag which isn't in Linus' nor Tony's trees yet. Is it possible to avoid consuming a page flag? If this is an ia64-only (or 64-bit-only) thing I guess we could use bit 32. > + if (page->flags & PG_uncached) dude. That ain't gonna work ;)