From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754692AbZBFFlP (ORCPT ); Fri, 6 Feb 2009 00:41:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752239AbZBFFk7 (ORCPT ); Fri, 6 Feb 2009 00:40:59 -0500 Received: from gate.crashing.org ([63.228.1.57]:56792 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751837AbZBFFk7 (ORCPT ); Fri, 6 Feb 2009 00:40:59 -0500 Subject: Re: [Bug #12608] 2.6.29-rc powerpc G5 Xorg legacy_mem regression From: Benjamin Herrenschmidt To: Hugh Dickins Cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Jesse Barnes In-Reply-To: <200902051433.23294.jbarnes@virtuousgeek.org> References: <1233867944.4612.104.camel@pasglop> <200902051433.23294.jbarnes@virtuousgeek.org> Content-Type: text/plain Date: Fri, 06 Feb 2009 16:40:36 +1100 Message-Id: <1233898836.4612.116.camel@pasglop> Mime-Version: 1.0 X-Mailer: Evolution 2.24.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2009-02-05 at 14:33 -0800, Jesse Barnes wrote: > One option there would be to provide the file but just use anonymous memory to > back it. X will happily think it's messing with legacy VGA memory, but it > shouldn't matter that it's not actually affecting hw. What about this (untested) patch ? powerpc/pci: mmap anonymous memory when legacy_mem doesn't exist The new legacy_mem file in sysfs is causing problems with X on machines that don't support legacy memory access. The way I initially implemented it, we would fail with -ENXIO when trying to mmap it, thus exposing to X that we do support the API but there is no legacy memory. Unfortunately, X poor error handling is causing it to fail to start when it gets this error. This implements a workaround hack that instead maps anonymous memory instead (using shmem if VM_SHARED is set, just like /dev/zero does). Signed-off-by: Benjamin Herrenschmidt --- Index: linux-work/arch/powerpc/kernel/pci-common.c =================================================================== --- linux-work.orig/arch/powerpc/kernel/pci-common.c 2009-02-06 16:23:36.000000000 +1100 +++ linux-work/arch/powerpc/kernel/pci-common.c 2009-02-06 16:30:32.000000000 +1100 @@ -561,8 +561,21 @@ int pci_mmap_legacy_page_range(struct pc (unsigned long long)(offset + size - 1)); if (mmap_state == pci_mmap_mem) { - if ((offset + size) > hose->isa_mem_size) - return -ENXIO; + /* Hack alert ! + * + * Because X is lame and can fail starting if it gets an error trying + * to mmap legacy_mem (instead of just moving on without legacy memory + * access) we fake it here by giving it anonymous memory, effectively + * behaving just like /dev/zero + */ + if ((offset + size) > hose->isa_mem_size) { + printk(KERN_DEBUG + "Process %s (pid:%d) mapped non-existing PCI legacy memory for 0%04x:%02x\n", + current->comm, current->pid, pci_domain_nr(bus), bus->number); + if (vma->vm_flags & VM_SHARED) + return shmem_zero_setup(vma); + return 0; + } offset += hose->isa_mem_phys; } else { unsigned long io_offset = (unsigned long)hose->io_base_virt - _IO_BASE;