From patchwork Thu Feb 21 11:50:12 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Sewior X-Patchwork-Id: 10823939 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 2BA796C2 for ; Thu, 21 Feb 2019 11:52:17 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 18742308C7 for ; Thu, 21 Feb 2019 11:52:17 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 0AB90308CC; Thu, 21 Feb 2019 11:52:17 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 95238308C7 for ; Thu, 21 Feb 2019 11:52:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727952AbfBULuz (ORCPT ); Thu, 21 Feb 2019 06:50:55 -0500 Received: from Galois.linutronix.de ([146.0.238.70]:45690 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727897AbfBULuu (ORCPT ); Thu, 21 Feb 2019 06:50:50 -0500 Received: from localhost ([127.0.0.1] helo=flow.W.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1gwmsG-0001RC-G6; Thu, 21 Feb 2019 12:50:44 +0100 From: Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Cc: x86@kernel.org, Andy Lutomirski , Paolo Bonzini , =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen , Sebastian Andrzej Siewior Subject: [PATCH 14/22] x86/fpu: Eager switch PKRU state Date: Thu, 21 Feb 2019 12:50:12 +0100 Message-Id: <20190221115020.12385-15-bigeasy@linutronix.de> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190221115020.12385-1-bigeasy@linutronix.de> References: <20190221115020.12385-1-bigeasy@linutronix.de> MIME-Version: 1.0 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 access to userspace memory while running in kernel mode also need to abide by the memory permissions specified in the protection keys. The "eager switch" is a preparation for loading the FPU state on return to userland. Instead of decoupling PKRU state from xstate I update PKRU within xstate on write operations by the kernel. The read/write_pkru() is moved to another header file so it can easily accessed from pgtable.h and fpu/internal.h. For user tasks we should always get the PKRU from the xsave area and it should not change anything because the PKRU value was loaded as part of FPU restore. For kernel kernel threads we now will have the default "allow everything" written. Before this commit the kernel thread would end up with a random value which it inherited from the previous user task. Signed-off-by: Rik van Riel [bigeasy: save pkru to xstate, no cache, don't use __raw_xsave_addr()] Signed-off-by: Sebastian Andrzej Siewior --- arch/x86/include/asm/fpu/internal.h | 20 ++++++++++++++++++-- arch/x86/include/asm/fpu/xstate.h | 1 + 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 67e4805bccb6f..05f6fce62e9f1 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -562,8 +562,24 @@ switch_fpu_prepare(struct fpu *old_fpu, int cpu) */ static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu) { - if (static_cpu_has(X86_FEATURE_FPU)) - __fpregs_load_activate(new_fpu, cpu); + struct pkru_state *pk; + u32 pkru_val = 0; + + if (!static_cpu_has(X86_FEATURE_FPU)) + return; + + __fpregs_load_activate(new_fpu, cpu); + + if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) + return; + + if (current->mm) { + pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU); + WARN_ON_ONCE(!pk); + if (pk) + pkru_val = pk->pkru; + } + __write_pkru(pkru_val); } /* diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h index fbe41f808e5d8..4e18a837223ff 100644 --- a/arch/x86/include/asm/fpu/xstate.h +++ b/arch/x86/include/asm/fpu/xstate.h @@ -5,6 +5,7 @@ #include #include #include +#include /* Bit 63 of XCR0 is reserved for future expansion */ #define XFEATURE_MASK_EXTEND (~(XFEATURE_MASK_FPSSE | (1ULL << 63)))