Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933828Ab3GPWz7 (ORCPT ); Tue, 16 Jul 2013 18:55:59 -0400 Received: from mail-lb0-f178.google.com ([209.85.217.178]:57382 "EHLO mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933387Ab3GPWz6 (ORCPT ); Tue, 16 Jul 2013 18:55:58 -0400 MIME-Version: 1.0 In-Reply-To: References: From: Andy Lutomirski Date: Tue, 16 Jul 2013 15:55:36 -0700 Message-ID: Subject: Re: [PATCH] BGRT: Don't ioremap if image address is in System RAM (was: Re: BGRT Pointer in System RAM) To: Parag Warudkar Cc: Josh Triplett , LKML , linux-acpi@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1730 Lines: 40 On Tue, Jul 16, 2013 at 3:15 PM, Parag Warudkar wrote: > On Mon, Jul 15, 2013 at 8:00 PM, Parag Warudkar wrote: >> On Mon, Jul 15, 2013 at 7:56 PM, Parag Warudkar wrote: >>> On Mon, Jul 15, 2013 at 7:04 PM, Josh Triplett wrote: >>> >>>> We do need to handle the case of a valid pointer into memory that e820 >>>> calls system RAM, as well as the case of a valid pointer into memory >>>> reserved for the BIOS or similar, but not the case of an invalid >>>> pointer. >>> >>> Would that be as simple as >>> >>> page_is_ram( >> >> Damn shortcuts - >> virt_addr = phys_to_virt(image->base_address); >> if(page_is_ram(virt_to_page(virt_addr))) { >> //direct read from virt addr >> } >> >> Would that suffice for the System RAM case or some other MM trickery >> is involved? > > Ok, so I played around with it a bit and the following patch works > fine on my system. (I.E. image size is reasonable, cat > /sys/firmware/acpi/bgrt/image > img.bmp generates a valid, > non-distorted bitmap, which it did before too, btw as despite of the > ioremap WARN_ON the ioremap seems to succeed if !(is_ram && > pfn_valid(pfn) && !PageReserved.) > How reliable is this? That is, is there any guarantee that nothing will have overwritten the image in memory before this code runs? --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/