From owner-svn-src-all@freebsd.org Thu Dec 5 19:25:50 2019 Return-Path: Delivered-To: svn-src-all@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 881951A98B5; Thu, 5 Dec 2019 19:25:50 +0000 (UTC) (envelope-from alc@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 47TQg239XQz4YMx; Thu, 5 Dec 2019 19:25:50 +0000 (UTC) (envelope-from alc@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 4F9F41DB24; Thu, 5 Dec 2019 19:25:50 +0000 (UTC) (envelope-from alc@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id xB5JPopn093038; Thu, 5 Dec 2019 19:25:50 GMT (envelope-from alc@FreeBSD.org) Received: (from alc@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id xB5JPoDY093037; Thu, 5 Dec 2019 19:25:50 GMT (envelope-from alc@FreeBSD.org) Message-Id: <201912051925.xB5JPoDY093037@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: alc set sender to alc@FreeBSD.org using -f From: Alan Cox Date: Thu, 5 Dec 2019 19:25:50 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r355427 - head/sys/arm64/arm64 X-SVN-Group: head X-SVN-Commit-Author: alc X-SVN-Commit-Paths: head/sys/arm64/arm64 X-SVN-Commit-Revision: 355427 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 Dec 2019 19:25:50 -0000 Author: alc Date: Thu Dec 5 19:25:49 2019 New Revision: 355427 URL: https://svnweb.freebsd.org/changeset/base/355427 Log: On a context switch, handle the possibility that the old thread was preempted after an "ic" or "tlbi" instruction but before it performed a "dsb" instruction. The "ic" and "tlbi" instructions have unusual synchronization requirements. If the old thread migrates to a new processor, its completion of a "dsb" instruction on that new processor does not guarantee that the "ic" or "tlbi" instructions performed on the old processor have completed. This issue is not restricted to the kernel. Since locore.S sets the UCI bit in SCTLR, user-space programs can perform "ic ivau" instructions (as well as some forms of the "dc" instruction). Reviewed by: andrew, kib, markj, mmel X-MFC with: r355145 Differential Revision: https://reviews.freebsd.org/D22622 Modified: head/sys/arm64/arm64/pmap.c Modified: head/sys/arm64/arm64/pmap.c ============================================================================== --- head/sys/arm64/arm64/pmap.c Thu Dec 5 18:47:29 2019 (r355426) +++ head/sys/arm64/arm64/pmap.c Thu Dec 5 19:25:49 2019 (r355427) @@ -5850,8 +5850,18 @@ pmap_activate_int(pmap_t pmap) KASSERT(PCPU_GET(curpmap) != NULL, ("no active pmap")); KASSERT(pmap != kernel_pmap, ("kernel pmap activation")); - if (pmap == PCPU_GET(curpmap)) + if (pmap == PCPU_GET(curpmap)) { + /* + * Handle the possibility that the old thread was preempted + * after an "ic" or "tlbi" instruction but before it performed + * a "dsb" instruction. If the old thread migrates to a new + * processor, its completion of a "dsb" instruction on that + * new processor does not guarantee that the "ic" or "tlbi" + * instructions performed on the old processor have completed. + */ + dsb(ish); return (false); + } /* * Ensure that the store to curpmap is globally visible before the