Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754973AbdGKE6b (ORCPT ); Tue, 11 Jul 2017 00:58:31 -0400 Received: from mail-ua0-f195.google.com ([209.85.217.195]:33267 "EHLO mail-ua0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754416AbdGKE6Z (ORCPT ); Tue, 11 Jul 2017 00:58:25 -0400 MIME-Version: 1.0 In-Reply-To: References: <20170707133804.29711.1616.stgit@tlendack-t1.amdoffice.net> <20170707133925.29711.39301.stgit@tlendack-t1.amdoffice.net> From: Brian Gerst Date: Tue, 11 Jul 2017 00:58:23 -0400 Message-ID: Subject: Re: [PATCH v9 07/38] x86/mm: Remove phys_to_virt() usage in ioremap() To: Tom Lendacky Cc: linux-arch , linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, "the arch/x86 maintainers" , kexec@lists.infradead.org, Linux Kernel Mailing List , kasan-dev@googlegroups.com, xen-devel@lists.xen.org, Linux-MM , iommu@lists.linux-foundation.org, Brijesh Singh , Toshimitsu Kani , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Matt Fleming , Alexander Potapenko , "H. Peter Anvin" , Larry Woodman , Jonathan Corbet , Joerg Roedel , "Michael S. Tsirkin" , Ingo Molnar , Andrey Ryabinin , Dave Young , Rik van Riel , Arnd Bergmann , Konrad Rzeszutek Wilk , Borislav Petkov , Andy Lutomirski , Boris Ostrovsky , Dmitry Vyukov , Juergen Gross , Thomas Gleixner , Paolo Bonzini Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2710 Lines: 72 On Mon, Jul 10, 2017 at 3:50 PM, Tom Lendacky wrote: > On 7/8/2017 7:57 AM, Brian Gerst wrote: >> >> On Fri, Jul 7, 2017 at 9:39 AM, Tom Lendacky >> wrote: >>> >>> Currently there is a check if the address being mapped is in the ISA >>> range (is_ISA_range()), and if it is, then phys_to_virt() is used to >>> perform the mapping. When SME is active, the default is to add pagetable >>> mappings with the encryption bit set unless specifically overridden. The >>> resulting pagetable mapping from phys_to_virt() will result in a mapping >>> that has the encryption bit set. With SME, the use of ioremap() is >>> intended to generate pagetable mappings that do not have the encryption >>> bit set through the use of the PAGE_KERNEL_IO protection value. >>> >>> Rather than special case the SME scenario, remove the ISA range check and >>> usage of phys_to_virt() and have ISA range mappings continue through the >>> remaining ioremap() path. >>> >>> Signed-off-by: Tom Lendacky >>> --- >>> arch/x86/mm/ioremap.c | 7 +------ >>> 1 file changed, 1 insertion(+), 6 deletions(-) >>> >>> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c >>> index 4c1b5fd..bfc3e2d 100644 >>> --- a/arch/x86/mm/ioremap.c >>> +++ b/arch/x86/mm/ioremap.c >>> @@ -13,6 +13,7 @@ >>> #include >>> #include >>> #include >>> +#include >>> >>> #include >>> #include >>> @@ -106,12 +107,6 @@ static void __iomem >>> *__ioremap_caller(resource_size_t phys_addr, >>> } >>> >>> /* >>> - * Don't remap the low PCI/ISA area, it's always mapped.. >>> - */ >>> - if (is_ISA_range(phys_addr, last_addr)) >>> - return (__force void __iomem *)phys_to_virt(phys_addr); >>> - >>> - /* >>> * Don't allow anybody to remap normal RAM that we're using.. >>> */ >>> pfn = phys_addr >> PAGE_SHIFT; >>> >> >> Removing this also affects 32-bit, which is more likely to access >> legacy devices in this range. Put in a check for SME instead > > > I originally had a check for SME here in a previous version of the > patch. Thomas Gleixner recommended removing the check so that the code > path was always exercised regardless of the state of SME in order to > better detect issues: > > http://marc.info/?l=linux-kernel&m=149803067811436&w=2 > > Thanks, > Tom Looking a bit closer, this shortcut doesn't set the caching attributes. So it's probably best to get rid of it anyways. Also note, there is a corresponding check in iounmap(). -- Brian Gerst