Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933865Ab3GPXca (ORCPT ); Tue, 16 Jul 2013 19:32:30 -0400 Received: from mail-lb0-f175.google.com ([209.85.217.175]:42721 "EHLO mail-lb0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933764Ab3GPXc2 (ORCPT ); Tue, 16 Jul 2013 19:32:28 -0400 MIME-Version: 1.0 In-Reply-To: References: From: Andy Lutomirski Date: Tue, 16 Jul 2013 16:32:06 -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: linux-acpi@vger.kernel.org, Linux Kernel Mailing List , Josh Triplett 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: 1829 Lines: 44 On Tue, Jul 16, 2013 at 4:23 PM, Parag Warudkar wrote: > > On Jul 16, 2013 6:55 PM, "Andy Lutomirski" wrote: > >> > 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? >> > From the little digging I did, this code runs fairly early in the boot > process, right after ACPI acquires all tables. If I am not mistaken it runs > as part of efi_late_init which should be before efi_free_boot_services() is > called. > > Image address on my system is 00000000B2E1B018. At boot EFI prints the > following - > > [ 0.000000] efi: mem23: type=4, attr=0xf, > range=[0x00000000b2c34000-0x00000000b2e5d0 > > Type=4, again if I am not mistaken is EFI_BOOT_SERVICES_DATA. So all put > together I think it should be reliable to read off of that address when > efi-bgrt-init runs, which is before the boot services code and data are > discarded. Fair enough. I leave it to the experts to comment on whether there should be some explicit check of whether this is EFI_BOOT_SERVICES_DATA. FWIW, if my board does indeed have a DWORD-swapped address, it's in plain old RAM (type=7). --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/