From patchwork Thu Feb 27 13:33:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 230182 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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 175EAC35677 for ; Thu, 27 Feb 2020 14:40:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D14EA24656 for ; Thu, 27 Feb 2020 14:40:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582814434; bh=GEmMPpyFw3qXbB0SaqXyk8IradjQvBJNQzdmisvUtZA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=cAknFeLZBbJLeQ0cQKcJ4/+6jw37rcStKCAXUhcyrMetsu7EchGwYQqjhE3XEhZUx lcKG2o0eww4ZhTd9BMnGxKKGbuzuz4LtyND3phEoXYAkFP7f0ifbbZDPBfWY6OmXPD OnFQcDvbtzpzLrElewBxV0tMC1WzqGhvzYSXUUto= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731292AbgB0NxE (ORCPT ); Thu, 27 Feb 2020 08:53:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:52782 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731624AbgB0NxD (ORCPT ); Thu, 27 Feb 2020 08:53:03 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3206D20578; Thu, 27 Feb 2020 13:53:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582811582; bh=GEmMPpyFw3qXbB0SaqXyk8IradjQvBJNQzdmisvUtZA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AR9wE32uE0kHOuTNic2h6vMwkNlcF82GMT2FCwV1c+Jnyt4gW0/eC6C81IkwI4PLe MwKXB2zjkCasKcSsI8F6ptQ5XuP3Im2/mQN45gPk5renqi+ms8dqSDy8ZdmnNLdEt+ XSGKDVfEhR1462vX6W3fbPtziL+4H6F7wtr+YEFQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Catalin Marinas , Srinivas Ramana , Marc Zyngier , Will Deacon Subject: [PATCH 4.14 022/237] arm64: ssbs: Fix context-switch when SSBS is present on all CPUs Date: Thu, 27 Feb 2020 14:33:56 +0100 Message-Id: <20200227132257.855894986@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200227132255.285644406@linuxfoundation.org> References: <20200227132255.285644406@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Will Deacon commit fca3d33d8ad61eb53eca3ee4cac476d1e31b9008 upstream. When all CPUs in the system implement the SSBS extension, the SSBS field in PSTATE is the definitive indication of the mitigation state. Further, when the CPUs implement the SSBS manipulation instructions (advertised to userspace via an HWCAP), EL0 can toggle the SSBS field directly and so we cannot rely on any shadow state such as TIF_SSBD at all. Avoid forcing the SSBS field in context-switch on such a system, and simply rely on the PSTATE register instead. Cc: Cc: Catalin Marinas Cc: Srinivas Ramana Fixes: cbdf8a189a66 ("arm64: Force SSBS on context switch") Reviewed-by: Marc Zyngier Signed-off-by: Will Deacon Signed-off-by: Greg Kroah-Hartman --- arch/arm64/kernel/process.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -354,6 +354,13 @@ static void ssbs_thread_switch(struct ta if (unlikely(next->flags & PF_KTHREAD)) return; + /* + * If all CPUs implement the SSBS extension, then we just need to + * context-switch the PSTATE field. + */ + if (cpu_have_feature(cpu_feature(SSBS))) + return; + /* If the mitigation is enabled, then we leave SSBS clear. */ if ((arm64_get_ssbd_state() == ARM64_SSBD_FORCE_ENABLE) || test_tsk_thread_flag(next, TIF_SSBD))