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=-15.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 7D161C4338F for ; Fri, 6 Aug 2021 12:01:01 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 36EBE60E78 for ; Fri, 6 Aug 2021 12:01:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 36EBE60E78 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=b3uLANQIrxs5RGtPehpNExXhPKhCGaO5JSISsXbhUcU=; b=ssN5W/Q7xSOGPq OLDGyWkKR47BpnX2W67G4oIIv/P+l7vhow88kO+iA9WnpbBMP59u27TYQYAhth2WnqFLRALe0j73P oo+pV0+mxexSsypwpP9uw8iPJEkGRLXiDC0vCnDyg5HUWUij9Z6Y4P0oPMX1Y3FpH1Isrteh+ZL2F f3cnkYvHHC7p18bHBQQl4SQxe+GWpy2XRNxZM4x/Air59Ll0emt6KZZ4FTvsrySTkrz1g3nEuayCh d/0Yl+lEE70WTGFEm8IqmkIMNYmM/wMDJO4mcdNhHdsADY4LvABg9sP5AQlbapizbzQ3uT6rmwpJZ XJpKXcTvGkAKPuQy+Nzg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mByVk-00CPES-Pp; Fri, 06 Aug 2021 11:59:36 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mByVh-00CPE2-0E for linux-arm-kernel@lists.infradead.org; Fri, 06 Aug 2021 11:59:34 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1E754610FF; Fri, 6 Aug 2021 11:59:30 +0000 (UTC) Date: Fri, 6 Aug 2021 12:59:28 +0100 From: Catalin Marinas To: Will Deacon Cc: linux-arm-kernel@lists.infradead.org, kernel-team@android.com, Marc Zyngier , Jade Alglave , Shameer Kolothum , kvmarm@lists.cs.columbia.edu, linux-arch@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/4] arm64: mm: Fix TLBI vs ASID rollover Message-ID: <20210806115927.GJ6719@arm.com> References: <20210806113109.2475-1-will@kernel.org> <20210806113109.2475-2-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210806113109.2475-2-will@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210806_045933_103658_7685E81E X-CRM114-Status: GOOD ( 16.37 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Aug 06, 2021 at 12:31:04PM +0100, Will Deacon wrote: > diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h > index 75beffe2ee8a..e9c30859f80c 100644 > --- a/arch/arm64/include/asm/mmu.h > +++ b/arch/arm64/include/asm/mmu.h > @@ -27,11 +27,32 @@ typedef struct { > } mm_context_t; > > /* > - * This macro is only used by the TLBI and low-level switch_mm() code, > - * neither of which can race with an ASID change. We therefore don't > - * need to reload the counter using atomic64_read(). > + * We use atomic64_read() here because the ASID for an 'mm_struct' can > + * be reallocated when scheduling one of its threads following a > + * rollover event (see new_context() and flush_context()). In this case, > + * a concurrent TLBI (e.g. via try_to_unmap_one() and ptep_clear_flush()) > + * may use a stale ASID. This is fine in principle as the new ASID is > + * guaranteed to be clean in the TLB, but the TLBI routines have to take > + * care to handle the following race: > + * > + * CPU 0 CPU 1 CPU 2 > + * > + * // ptep_clear_flush(mm) > + * xchg_relaxed(pte, 0) > + * DSB ISHST > + * old = ASID(mm) We'd need specs clarified (ARM ARM, cat model) that the DSB ISHST is sufficient to order the pte write with the subsequent ASID read. Otherwise the patch looks fine to me: Reviewed-by: Catalin Marinas _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel