From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Wed, 17 Apr 2002 19:35:00 +0000 Subject: Re: [Linux-ia64] Patch to fix lfetches accessing beyond a page (copy_page/clear_pa Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Wed, 17 Apr 2002 11:51:15 -0700, "Mallick, Asit K" said: Asit> Here is a patch fix the lfetches accessing beyond a page that Asit> can have a side effect of generating an MCA if the physical Asit> memory does not exist. For example, copy_page will try to Asit> access video memory for the page that ends at 640K and this Asit> can cause MCA for some platforms. Some of the Bigsur UP boot Asit> failures were root caused to this problem. Asit> Both copy page and clear_page are very performance critical Asit> functions and tuned for both Itanium and McKinley. The patch Asit> is implemented using unused slots (nops) and has no Asit> performance impact. Asit> For kernels 2.4.18 and higher you will just need the patch for Asit> copy_page(). clear_page and McKinley optimized copy_page has Asit> been already taken care. This patch only papers over the real problem, which is that there shouldn't be a WB translation covering anything other than normal memory in the first place. I don't want to apply hack upon hack, just so it works for another while. Let's fix this one permanently. I think we may just have to bite the bullet and treat the <64MB specially in the alternate TLB handlers. If we use a 4KB page size for that area, we should be good (assuming DIG goes ahead and does something sane about requiring a minimum granularity for physical memory). --david