From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [PATCH 10/28] i386: map enough initial memory to create lowmem mappings Date: Mon, 23 Apr 2007 11:06:48 -0700 Message-ID: <462CF5B8.4070708@xensource.com> References: <20070414204154.871250608@goop.org> <200704192250.52633.ak@suse.de> <4627D756.5020405@zytor.com> <200704192304.01053.ak@suse.de> <4627DB0C.2010804@zytor.com> <4627DDAD.4070805@redhat.com> <4627E099.209@goop.org> <462CE027.4030302@goop.org> <462CE1E0.9060007@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: "Eric W. Biederman" Cc: "H. Peter Anvin" , lkml , Chris Wright , virtualization@lists.osdl.org, Chuck Ebbert , Andrew Morton , Linus Torvalds List-Id: virtualization@lists.linuxfoundation.org Eric W. Biederman wrote: > Consider a memory hole of size 8M immediately after our bootmem bitmap. > head.S which knows nothing of holes will map the pages of the hole > into the initial page tables assuming that is where the page tables > will live. > Sure, but considering we're only talking about mapping an additional *2* pages, the chances are that it will affect a kernel as much as the early head.S mapping. It's well within the variability of fairly similar kernel configs. > As for how to fix this, we need to call boot_ioremap or better > bt_ioremap on the address returned from alloc_bootmem_pages_low to > force the allocated page into the page table. After we have setup > the page table page we can call unmap the page to free up the scarce > early mapping resource. > Would that be necessary? Is there any need to remap it? Couldn't you just do the straightforward phys->virt mapping and use the page where it lies? J