From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f200.google.com (mail-pf0-f200.google.com [209.85.192.200]) by kanga.kvack.org (Postfix) with ESMTP id 2965E6B0517 for ; Tue, 11 Jul 2017 11:02:19 -0400 (EDT) Received: by mail-pf0-f200.google.com with SMTP id y62so2036440pfa.3 for ; Tue, 11 Jul 2017 08:02:19 -0700 (PDT) Received: from NAM01-BY2-obe.outbound.protection.outlook.com (mail-by2nam01on0053.outbound.protection.outlook.com. [104.47.34.53]) by mx.google.com with ESMTPS id v80si106622pgb.578.2017.07.11.08.02.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 11 Jul 2017 08:02:17 -0700 (PDT) Subject: Re: [PATCH v9 07/38] x86/mm: Remove phys_to_virt() usage in ioremap() References: <20170707133804.29711.1616.stgit@tlendack-t1.amdoffice.net> <20170707133925.29711.39301.stgit@tlendack-t1.amdoffice.net> From: Tom Lendacky Message-ID: <81fbf5db-c42f-cfe6-5d31-d60adbd18f26@amd.com> Date: Tue, 11 Jul 2017 10:02:05 -0500 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Brian Gerst 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 On 7/10/2017 11:58 PM, Brian Gerst wrote: > 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(). Good catch. I'll update the patch to include the removal of the ISA checks in the iounmap() path as well. Thanks, Tom > > -- > Brian Gerst > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org