From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2B725C4646A for ; Wed, 12 Sep 2018 14:18:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D287120839 for ; Wed, 12 Sep 2018 14:18:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D287120839 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727473AbeILTXd (ORCPT ); Wed, 12 Sep 2018 15:23:33 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:60246 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726537AbeILTXc (ORCPT ); Wed, 12 Sep 2018 15:23:32 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 323F885783; Wed, 12 Sep 2018 14:18:49 +0000 (UTC) Received: from [10.36.118.61] (unknown [10.36.118.61]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 13F1B108786; Wed, 12 Sep 2018 14:18:45 +0000 (UTC) Subject: Re: [RFC PATCH 04/10] x86/fpu: eager switch PKRU state To: Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org Cc: x86@kernel.org, Andy Lutomirski , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel References: <20180912133353.20595-1-bigeasy@linutronix.de> <20180912133353.20595-5-bigeasy@linutronix.de> From: Paolo Bonzini Openpgp: preference=signencrypt Autocrypt: addr=pbonzini@redhat.com; prefer-encrypt=mutual; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0f UGFvbG8gQm9uemluaSA8Ym9uemluaUBnbnUub3JnPsLBTQQTAQIAIwUCVEJ7AwIbAwcLCQgH AwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEH4VEAzNNmmxNcwOniaZVLsuy1lW/ntYCA0Caz0i sHpmecK8aWlvL9wpQCk4GlOX9L1emyYXZPmzIYB0IRqmSzAlZxi+A2qm9XOxs5gJ2xqMEXX5 FMtUH3kpkWWJeLqe7z0EoQdUI4EG988uv/tdZyqjUn2XJE+K01x7r3MkUSFz/HZKZiCvYuze VlS0NTYdUt5jBXualvAwNKfxEkrxeHjxgdFHjYWhjflahY7TNRmuqPM/Lx7wAuyoDjlYNE40 Z+Kun4/KjMbjgpcF4Nf3PJQR8qXI6p3so2qsSn91tY7DFSJO6v2HwFJkC2jU95wxfNmTEUZc znXahYbVOwCDJRuPrE5GKFd/XJU9u5hNtr/uYipHij01WXal2cce1S5mn1/HuM1yo1u8xdHy IupCd57EWI948e8BlhpujUCU2tzOb2iYS0kpmJ9/oLVZrOcSZCcCl2P0AaCAsj59z2kwQS9D du0WxUs8waso0Qq6tDEHo8yLCOJDzSz4oojTtWe4zsulVnWV+wu70AioemAT8S6JOtlu60C5 dHgQUD1Tp+ReXpDKXmjbASJx4otvW0qah3o6JaqO79tbDqIvncu3tewwp6c85uZd48JnIOh3 utBAu684nJakbbvZUGikJfxd887ATQRUQnHuAQgAx4dxXO6/Zun0eVYOnr5GRl76+2UrAAem Vv9Yfn2PbDIbxXqLff7oyVJIkw4WdhQIIvvtu5zH24iYjmdfbg8iWpP7NqxUQRUZJEWbx2CR wkMHtOmzQiQ2tSLjKh/cHeyFH68xjeLcinR7jXMrHQK+UCEw6jqi1oeZzGvfmxarUmS0uRuf fAb589AJW50kkQK9VD/9QC2FJISSUDnRC0PawGSZDXhmvITJMdD4TjYrePYhSY4uuIV02v02 8TVAaYbIhxvDY0hUQE4r8ZbGRLn52bEzaIPgl1p/adKfeOUeMReg/CkyzQpmyB1TSk8lDMxQ zCYHXAzwnGi8WU9iuE1P0wARAQABwsEzBBgBAgAJBQJUQnHuAhsMAAoJEH4VEAzNNmmxp1EO oJy0uZggJm7gZKeJ7iUpeX4eqUtqelUw6gU2daz2hE/jsxsTbC/w5piHmk1H1VWDKEM4bQBT uiJ0bfo55SWsUNN+c9hhIX+Y8LEe22izK3w7mRpvGcg+/ZRG4DEMHLP6JVsv5GMpoYwYOmHn plOzCXHvmdlW0i6SrMsBDl9rw4AtIa6bRwWLim1lQ6EM3PWifPrWSUPrPcw4OLSwFk0CPqC4 HYv/7ZnASVkR5EERFF3+6iaaVi5OgBd81F1TCvCX2BEyIDRZLJNvX3TOd5FEN+lIrl26xecz 876SvcOb5SL5SKg9/rCBufdPSjojkGFWGziHiFaYhbuI2E+NfWLJtd+ZvWAAV+O0d8vFFSvr iy9enJ8kxJwhC0ECbSKFY+W1eTIhMD3aeAKY90drozWEyHhENf4l/V+Ja5vOnW+gCDQkGt2Y 1lJAPPSIqZKvHzGShdh8DduC0U3xYkfbGAUvbxeepjgzp0uEnBXfPTy09JGpgWbg0w91GyfT /ujKaGd4vxG2Ei+MMNDmS1SMx7wu0evvQ5kT9NPzyq8R2GIhVSiAd2jioGuTjX6AZCFv3ToO 53DliFMkVTecLptsXaesuUHgL9dKIfvpm+rNXRn9wAwGjk0X/A== Message-ID: <8e5b64e4-b3e6-f884-beb6-b7b69ab2d8c1@redhat.com> Date: Wed, 12 Sep 2018 16:18:44 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180912133353.20595-5-bigeasy@linutronix.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Wed, 12 Sep 2018 14:18:49 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Wed, 12 Sep 2018 14:18:49 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'pbonzini@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/09/2018 15:33, Sebastian Andrzej Siewior wrote: > From: Rik van Riel > > While most of a task's FPU state is only needed in user space, > the protection keys need to be in place immediately after a > context switch. > > The reason is that any accesses to userspace memory while running > in kernel mode also need to abide by the memory permissions > specified in the protection keys. > > The pkru info is put in its own cache line in the fpu struct because > that cache line is accessed anyway at context switch time, and the > location of the pkru info in the xsave buffer changes depending on > what other FPU registers are in use if the CPU uses compressed xsave > state (on by default). > > The initial state of pkru is zeroed out automatically by fpstate_init. > > Signed-off-by: Rik van Riel > [bigeasy: load PKRU state only if we also load FPU content] > Signed-off-by: Sebastian Andrzej Siewior > --- > arch/x86/include/asm/fpu/internal.h | 11 +++++++++-- > arch/x86/include/asm/fpu/types.h | 10 ++++++++++ > arch/x86/include/asm/pgtable.h | 6 +----- > arch/x86/mm/pkeys.c | 14 ++++++++++++++ > 4 files changed, 34 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h > index 16c4077ffc945..57bd1576e033d 100644 > --- a/arch/x86/include/asm/fpu/internal.h > +++ b/arch/x86/include/asm/fpu/internal.h > @@ -573,8 +573,15 @@ static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu) > bool preload = static_cpu_has(X86_FEATURE_FPU) && > new_fpu->initialized; > > - if (preload) > - __fpregs_load_activate(new_fpu, cpu); > + if (!preload) > + return; > + > + __fpregs_load_activate(new_fpu, cpu); > + /* Protection keys need to be in place right at context switch time. */ > + if (boot_cpu_has(X86_FEATURE_OSPKE)) { > + if (new_fpu->pkru != __read_pkru()) > + __write_pkru(new_fpu->pkru); > + } > } > > /* > diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h > index 202c53918ecfa..6fa58d37938d2 100644 > --- a/arch/x86/include/asm/fpu/types.h > +++ b/arch/x86/include/asm/fpu/types.h > @@ -293,6 +293,16 @@ struct fpu { > */ > unsigned int last_cpu; > > + /* > + * Protection key bits. These also live inside fpu.state.xsave, > + * but the location varies if the CPU uses the compressed format > + * for XSAVE(OPT). > + * > + * The protection key needs to be switched out immediately at context > + * switch time, so it is in place for things like copy_to_user. > + */ > + unsigned int pkru; > + > /* > * @initialized: > * > diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h > index 690c0307afed0..cc36f91011ad7 100644 > --- a/arch/x86/include/asm/pgtable.h > +++ b/arch/x86/include/asm/pgtable.h > @@ -132,11 +132,7 @@ static inline u32 read_pkru(void) > return 0; > } > > -static inline void write_pkru(u32 pkru) > -{ > - if (boot_cpu_has(X86_FEATURE_OSPKE)) > - __write_pkru(pkru); > -} > +extern void write_pkru(u32 pkru); > > static inline int pte_young(pte_t pte) > { > diff --git a/arch/x86/mm/pkeys.c b/arch/x86/mm/pkeys.c > index 6e98e0a7c9231..c7a7b6bd64009 100644 > --- a/arch/x86/mm/pkeys.c > +++ b/arch/x86/mm/pkeys.c > @@ -18,6 +18,20 @@ > > #include /* boot_cpu_has, ... */ > #include /* vma_pkey() */ > +#include > + > +void write_pkru(u32 pkru) > +{ > + if (!boot_cpu_has(X86_FEATURE_OSPKE)) > + return; > + > + current->thread.fpu.pkru = pkru; > + > + __fpregs_changes_begin(); > + __fpregs_load_activate(¤t->thread.fpu, smp_processor_id()); > + __write_pkru(pkru); > + __fpregs_changes_end(); > +} > > int __execute_only_pkey(struct mm_struct *mm) > { > I think you can go a step further and exclude PKRU state from copy_kernel_to_fpregs altogether; you just use RDPKRU/WRPKRU. This also means you don't need to call __fpregs_* functions in write_pkru. Thanks, Paolo