From patchwork Thu Oct 4 14:05:41 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 10626223 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 D8EBD15E2 for ; Thu, 4 Oct 2018 14:06:46 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C8AFE291BC for ; Thu, 4 Oct 2018 14:06:46 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BCCCF291CD; Thu, 4 Oct 2018 14:06:46 +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 501DE291BC for ; Thu, 4 Oct 2018 14:06:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727746AbeJDU7f (ORCPT ); Thu, 4 Oct 2018 16:59:35 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:36296 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727380AbeJDU7f (ORCPT ); Thu, 4 Oct 2018 16:59:35 -0400 Received: from localhost ([127.0.0.1] helo=bazinga.breakpoint.cc) by Galois.linutronix.de with esmtp (Exim 4.80) (envelope-from ) id 1g84GR-0002ic-8G; Thu, 04 Oct 2018 16:06:03 +0200 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 05/11] x86/fpu: set PKRU state for kernel threads Date: Thu, 4 Oct 2018 16:05:41 +0200 Message-Id: <20181004140547.13014-6-bigeasy@linutronix.de> X-Mailer: git-send-email 2.19.0 In-Reply-To: <20181004140547.13014-1-bigeasy@linutronix.de> References: <20181004140547.13014-1-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 The PKRU value is not set for kernel threads because they do not have the ->initialized value set. As a result the kernel thread has a random PKRU value set which it inherits from the previous task. It has been suggested by Paolo Bonzini to set it for kernel threads, too because it might be a fix. I *think* this is not required because the kernel threads don't copy data to/from userland and don't have access to any userspace mm in general. However there is this use_mm(). If we gain a mm by use_mm() we don't have a matching PKRU value because those are per thread. It has been suggested to use 0 as the PKRU value but this would bypass PKRU. Set the initial (default) PKRU value for kernel threads. Suggested-by: Paolo Bonzini Signed-off-by: Sebastian Andrzej Siewior --- arch/x86/include/asm/fpu/internal.h | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 956d967ca824a..4ecaf4d22954e 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -14,6 +14,7 @@ #include #include #include +#include #include #include @@ -573,20 +574,23 @@ static inline void switch_fpu_finish(struct fpu *new_fpu, int cpu) bool load_fpu; load_fpu = static_cpu_has(X86_FEATURE_FPU) && new_fpu->initialized; - if (!load_fpu) - return; - - __fpregs_load_activate(new_fpu, cpu); - #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS if (static_cpu_has(X86_FEATURE_OSPKE)) { struct pkru_state *pk; - pk = __raw_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU); - if (pk->pkru != __read_pkru()) - __write_pkru(pk->pkru); + if (!load_fpu) { + pkru_set_init_value(); + } else { + pk = __raw_xsave_addr(&new_fpu->state.xsave, + XFEATURE_PKRU); + if (pk->pkru != __read_pkru()) + __write_pkru(pk->pkru); + } } #endif + if (!load_fpu) + return; + __fpregs_load_activate(new_fpu, cpu); } /*