From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id D54016B0292 for ; Wed, 21 Jun 2017 14:30:31 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id b9so166159717pfl.0 for ; Wed, 21 Jun 2017 11:30:31 -0700 (PDT) Received: from NAM03-BY2-obe.outbound.protection.outlook.com (mail-by2nam03on0062.outbound.protection.outlook.com. [104.47.42.62]) by mx.google.com with ESMTPS id u91si14530308plb.586.2017.06.21.11.30.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 21 Jun 2017 11:30:31 -0700 (PDT) Subject: Re: [PATCH v7 08/36] x86/mm: Add support to enable SME in early boot processing References: <20170616184947.18967.84890.stgit@tlendack-t1.amdoffice.net> <20170616185115.18967.79622.stgit@tlendack-t1.amdoffice.net> <8d3c215f-cdad-5554-6e9c-5598e1081850@amd.com> From: Tom Lendacky Message-ID: Date: Wed, 21 Jun 2017 13:30:19 -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: Thomas Gleixner Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, xen-devel@lists.xen.org, linux-mm@kvack.org, 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 , Paolo Bonzini On 6/21/2017 10:38 AM, Thomas Gleixner wrote: > On Wed, 21 Jun 2017, Tom Lendacky wrote: >> On 6/21/2017 2:16 AM, Thomas Gleixner wrote: >>> Why is this an unconditional function? Isn't the mask simply 0 when the MEM >>> ENCRYPT support is disabled? >> >> I made it unconditional because of the call from head_64.S. I can't make >> use of the C level static inline function and since the mask is not a >> variable if CONFIG_AMD_MEM_ENCRYPT is not configured (#defined to 0) I >> can't reference the variable directly. >> >> I could create a #define in head_64.S that changes this to load rax with >> the variable if CONFIG_AMD_MEM_ENCRYPT is configured or a zero if it's >> not or add a #ifdef at that point in the code directly. Thoughts on >> that? > > See below. > >>> That does not make any sense. Neither the call to sme_encrypt_kernel() nor >>> the following call to sme_get_me_mask(). >>> >>> __startup_64() is already C code, so why can't you simply call that from >>> __startup_64() in C and return the mask from there? >> >> I was trying to keep it explicit as to what was happening, but I can >> move those calls into __startup_64(). > > That's much preferred. And the return value wants to be documented in both > C and ASM code. Will do. > >> I'll still need the call to sme_get_me_mask() in the secondary_startup_64 >> path, though (depending on your thoughts to the above response). > > call verify_cpu > > movq $(init_top_pgt - __START_KERNEL_map), %rax > > So if you make that: > > /* > * Sanitize CPU configuration and retrieve the modifier > * for the initial pgdir entry which will be programmed > * into CR3. Depends on enabled SME encryption, normally 0. > */ > call __startup_secondary_64 > > addq $(init_top_pgt - __START_KERNEL_map), %rax > > You can hide that stuff in C-code nicely without adding any cruft to the > ASM code. > Moving the call to verify_cpu into the C-code might be quite a bit of change. Currently, the verify_cpu code is included code and not a global function. I can still do the __startup_secondary_64() function and then look to incorporate verify_cpu into both __startup_64() and __startup_secondary_64() as a post-patch to this series. At least the secondary path will have a base C routine to which modifications can be made in the future if needed. How does that sound? Thanks, Tom > Thanks, > > tglx > -- 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