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=-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=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 1B6BAC34026 for ; Tue, 18 Feb 2020 20:01:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DA9F42465D for ; Tue, 18 Feb 2020 20:01:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582056087; bh=gXlqe2ZJceVqgHl8SGNURvfC+AiCU2Ij8n9ZA2sMH2Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=CvZvXeEuQixkOPnRo7jfNuKgoaOzcw1yjXtroIY8BDanxYowULl+8BmXv3eh7tnlU /aT+RRt+vlFK6BF0bSKIO3ftFXl+8BdviYTJs1OOcGqpUZryUiESC1yXM8k+5/pGUO 9UwsQaN6JaCjiwfaai4KDMbtVuyNeM5oCygp/5IU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728576AbgBRUBZ (ORCPT ); Tue, 18 Feb 2020 15:01:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:40954 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728752AbgBRUBV (ORCPT ); Tue, 18 Feb 2020 15:01:21 -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 BAC9824670; Tue, 18 Feb 2020 20:01:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582056081; bh=gXlqe2ZJceVqgHl8SGNURvfC+AiCU2Ij8n9ZA2sMH2Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rw7sYefGQd/goG4OovIR9gzH63LeuZ0A6T5ukvWPdcMBWcW23k6lnfKMBPDyxOzGK wegVdq3VWjIe7xjyk+hoNVgJRpLXR3RqQ17CtIuybF0PlHnQ9F2VoIKRBbn2rnreoQ W+eZfPybQiDCcu3/xImRZzrbJHe5JblQdzKAb6dQ= 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 5.5 27/80] arm64: ssbs: Fix context-switch when SSBS is present on all CPUs Date: Tue, 18 Feb 2020 20:54:48 +0100 Message-Id: <20200218190435.049644874@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200218190432.043414522@linuxfoundation.org> References: <20200218190432.043414522@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 @@ -466,6 +466,13 @@ 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))