From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757637Ab1ILOwO (ORCPT ); Mon, 12 Sep 2011 10:52:14 -0400 Received: from arkanian.console-pimps.org ([212.110.184.194]:44326 "EHLO arkanian.console-pimps.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757163Ab1ILOwN (ORCPT ); Mon, 12 Sep 2011 10:52:13 -0400 Subject: Re: [PATCH] EFI: Do not use __pa() to get the physical address of an ioremapped memory range From: Matt Fleming To: huang ying Cc: Zhang Rui , LKML , Matthew Garrett , x86@kernel.org In-Reply-To: References: <1314860114.32522.3.camel@rui> <1314864889.13161.4.camel@rui> <1314880125.8038.39.camel@mfleming-mobl1.ger.corp.intel.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 12 Sep 2011 15:52:10 +0100 Message-ID: <1315839130.3466.6.camel@mfleming-mobl1.ger.corp.intel.com> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 (2.32.2-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-09-02 at 13:12 +0800, huang ying wrote: > On Thu, Sep 1, 2011 at 8:28 PM, Matt Fleming wrote: > > > > Hmm.. does anyone know why we ioremap_cache() the memory on > > CONFIG_X86_32 instead of ioremap_nocache()? In the case of > > EFI_MEMORY_MAPPED_IO the memory really needs to be uncached. Then if > > we've ioremap'd the memory we should skip set_memory_uc() altogether, > > no? > > Because whether the mapping should be cached is determined by md->attr > instead of md->type. And besides UC, we may add WC, etc support. Confused. The CONFIG_X86_64 version of efi_ioremap() looks like this, void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size, u32 type) { unsigned long last_map_pfn; if (type == EFI_MEMORY_MAPPED_IO) return ioremap(phys_addr, size); Which uses md->type to figure out if we should call ioremap(), which on x86 is #define'd to ioremap_nocache(). CONFIG_X86_32 doesn't do this, but it looks to me like it should. Zhang, I agree that calling __pa() on an ioremap()'d region is bogus, but I don't understand why no one is seeing this crash on x86-64. Is it something to do with the x86-64 memory map layout such that __pa() works on an ioremap()'d address? -- Matt Fleming, Intel Open Source Technology Center