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=-8.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 4A47EC3A5A9 for ; Mon, 4 May 2020 20:48:15 +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 1E02E206A4 for ; Mon, 4 May 2020 20:48:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="efxtMGnC"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="xWVk+Kqa" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1E02E206A4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject: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=USY4CAxJ0FLwHP6l6yUKwaM79X/hjCltk71KLexjC30=; b=efxtMGnCzkcTFw CGxriaU2yqVxoTmD27Xo8FM7kFpQmYPcg2G1wwz5/ecobPFkyAlgP3YZj+vC0c9PFBYehzbmTI8Kw FHnhBbqF95fiIuu4OOzksMEPPEC0jSCD9q6lTXrfzdkImOHwcdfBdK2KP4SKnZY9iCVLekWrqMdWr eypNbfijAmCa8iS3hfUpnp3/o4sqxafHvuQ1YfUVs2M3UVmwaE7Rl1vhhK4PJ8bdRyWJxZCLgK32o i4LGjru6ccEvlFAq+71aMRK7+sOwNt78063Rp7Fu2Yh9+T9SSp2ZtOWzbK7c8uxQN46gaEQJpZfaS OP9flQxijNU3ZKJzm/BQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jVi0Z-0006ai-Ku; Mon, 04 May 2020 20:48:11 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jVi0X-0006a1-Dl for linux-arm-kernel@lists.infradead.org; Mon, 04 May 2020 20:48:10 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 B7E01206A4; Mon, 4 May 2020 20:48:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588625289; bh=uhstx6i6VStcX5tnxEtH4iTtQS0OGgGawfl0YTLt7FM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=xWVk+KqavPLzos8trQkkwJKJqC1RRw0zo6X3ZZmPzXdB1Z3iDAZMvN0af3UToUUiF FeBKcul0IpAF/yLlCvP3KXWqB79UXjuFKubP6LkstHKFXB/97OeV862n3tG8I19fFc 4KFxgu7ymxHTr0OJVpfzNHafDm1zUTDqmKi4dFCo= Date: Mon, 4 May 2020 21:48:04 +0100 From: Will Deacon To: Daniel Thompson Subject: Re: [PATCH v2] arm64: cacheflush: Fix KGDB trap detection Message-ID: <20200504204803.GA5657@willie-the-truck> References: <20200504170518.2959478-1-daniel.thompson@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200504170518.2959478-1-daniel.thompson@linaro.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-20200504_134809_484482_63FB21B4 X-CRM114-Status: GOOD ( 21.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: patches@linaro.org, Catalin Marinas , linux-kernel@vger.kernel.org, Douglas Anderson , Jason Wessel , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, May 04, 2020 at 06:05:18PM +0100, Daniel Thompson wrote: > flush_icache_range() contains a bodge to avoid issuing IPIs when the kgdb > trap handler is running because issuing IPIs is unsafe (and not needed) > in this execution context. However the current test, based on > kgdb_connected is flawed: it both over-matches and under-matches. > > The over match occurs because kgdb_connected is set when gdb attaches > to the stub and remains set during normal running. This is relatively > harmelss because in almost all cases irq_disabled() will be false. > > The under match is more serious. When kdb is used instead of kgdb to access > the debugger then kgdb_connected is not set in all the places that the > debug core updates sw breakpoints (and hence flushes the icache). This > can lead to deadlock. > > Fix by replacing the ad-hoc check with the proper kgdb macro. This also > allows us to drop the #ifdef wrapper. > > Fixes: 3b8c9f1cdfc5 ("arm64: IPI each CPU after invalidating the I-cache for kernel mappings") > Signed-off-by: Daniel Thompson > Reviewed-by: Douglas Anderson > --- > > Notes: > v2: Improve the commit message based based on feedback from Doug > Anderson > > arch/arm64/include/asm/cacheflush.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h > index e6cca3d4acf7..ce50c1f1f1ea 100644 > --- a/arch/arm64/include/asm/cacheflush.h > +++ b/arch/arm64/include/asm/cacheflush.h > @@ -79,7 +79,7 @@ static inline void flush_icache_range(unsigned long start, unsigned long end) > * IPI all online CPUs so that they undergo a context synchronization > * event and are forced to refetch the new instructions. > */ > -#ifdef CONFIG_KGDB > + > /* > * KGDB performs cache maintenance with interrupts disabled, so we > * will deadlock trying to IPI the secondary CPUs. In theory, we can > @@ -89,9 +89,9 @@ static inline void flush_icache_range(unsigned long start, unsigned long end) > * the patching operation, so we don't need extra IPIs here anyway. > * In which case, add a KGDB-specific bodge and return early. > */ > - if (kgdb_connected && irqs_disabled()) > + if (in_dbg_master()) Does this imply that irqs are disabled? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel