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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 80025C433DB for ; Sat, 27 Feb 2021 10:42:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 519C864EC0 for ; Sat, 27 Feb 2021 10:42:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230113AbhB0Kml (ORCPT ); Sat, 27 Feb 2021 05:42:41 -0500 Received: from foss.arm.com ([217.140.110.172]:43000 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230075AbhB0Kmf (ORCPT ); Sat, 27 Feb 2021 05:42:35 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0D085106F; Sat, 27 Feb 2021 02:41:49 -0800 (PST) Received: from monolith.localdoman (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6AF133F73B; Sat, 27 Feb 2021 02:41:48 -0800 (PST) From: Alexandru Elisei To: drjones@redhat.com, kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Subject: [kvm-unit-tests PATCH 1/6] arm64: Remove unnecessary ISB when writing to SPSel Date: Sat, 27 Feb 2021 10:41:56 +0000 Message-Id: <20210227104201.14403-2-alexandru.elisei@arm.com> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210227104201.14403-1-alexandru.elisei@arm.com> References: <20210227104201.14403-1-alexandru.elisei@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Software can use the SPSel operand to write directly to PSTATE.SP. According to ARM DDI 0487F.b, page D1-2332, writes to PSTATE are self-synchronizing and no ISB is needed: "Writes to the PSTATE fields have side-effects on various aspects of the PE operation. All of these side-effects are guaranteed: - Not to be visible to earlier instructions in the execution stream. - To be visible to later instructions in the execution stream." Signed-off-by: Alexandru Elisei --- arm/cstart64.S | 1 - 1 file changed, 1 deletion(-) diff --git a/arm/cstart64.S b/arm/cstart64.S index 0428014aa58a..fc1930bcdb53 100644 --- a/arm/cstart64.S +++ b/arm/cstart64.S @@ -54,7 +54,6 @@ start: /* set up stack */ mov x4, #1 msr spsel, x4 - isb adrp x4, stackptr add sp, x4, :lo12:stackptr -- 2.30.1