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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 3BB7BC7115B for ; Mon, 16 Jun 2025 17:10:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Content-Transfer-Encoding:Content-Type:In-Reply-To:From:References:To:Subject :MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=K0uYI/Yt9kTpet11sTd2e5MM0JBZfWAXMdid3EX/Ftw=; b=T9K/Mq8cJtmi22 m64SZHeBc4Qre1KqLbcXylYjZr1WI+Gw9rGEymCjx2eVTLHvwig4TvVOVIU7c5RKw32kdPvmGo09C kCoZ1GgYcP9JGp7nl4LykgmK1tVIfLoeyX5XcQaY9SAudwwWGunI1SGckkKyZUQkTNxUoD3zEsVC5 IfT3xeXnJE9z95BXyrjG/wVPJ5nIdhw+r/T0tV9YcNuNW8CCQtY3biGRsMk6IWVLpk80lSATccYu6 OgRkC4jGxgpsjmJOEefM/rndYK0YijEnnI3EcuoJGoLYyYVAP6GEiqMkAYvhPtgampjy1TjMWrw4b sAimWtzEAXH+WX3f4pfQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uRDLL-000000054qm-0V7P; Mon, 16 Jun 2025 17:09:59 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uRBQf-00000004nZF-0FuW for linux-arm-kernel@lists.infradead.org; Mon, 16 Jun 2025 15:07:22 +0000 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 8D41C150C; Mon, 16 Jun 2025 08:06:56 -0700 (PDT) Received: from [10.1.26.178] (e137867.arm.com [10.1.26.178]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 40E3D3F673; Mon, 16 Jun 2025 08:07:16 -0700 (PDT) Message-ID: Date: Mon, 16 Jun 2025 16:07:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 00/13] arm64: debug: remove hook registration, split exception entry To: "Luis Claudio R. Goncalves" References: <20250609173413.132168-1-ada.coupriediaz@arm.com> From: Ada Couprie Diaz Content-Language: en-US Organization: Arm Ltd. In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250616_080721_172700_F2FD6AC4 X-CRM114-Status: GOOD ( 17.29 ) 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: , Cc: Mark Rutland , Catalin Marinas , Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 12/06/2025 19:18, Luis Claudio R. Goncalves wrote: > On Mon, Jun 09, 2025 at 06:34:00PM +0100, Ada Couprie Diaz wrote: >> [...] >> >> PREEMPT_RT >> === >> >> Of note, this allows us to make the single exception handling mostly >> preemptible coming from EL0 in patch 9, fixing an issue with PREEMPT_RT[0]. >> The commit message details the reasoning on why this should be safe. >> It is *definitely* not preemptible at EL1 in the current state, given >> that the EL1 software step exception is handled by KGDB. >> >> CC-ing Luis as he did a lot of testing on v2 and originally >> reported the issue. >> >> Cc: "Luis Claudio R. Goncalves" >> >> We can do the same for the software break exception coming from EL0, >> which works in a very similar way. >> >> However, the hardware breakpoint and watchpoint exceptions also have >> a sleeping while non-preemptible issue with PREEMPT_RT, but this is >> much trickier to fix, so this won't be fixed in this series. >> A bit more details in [1]. >> >> I hesitated to add comments within the BRK64 and single-step handlers, >> on the EL0 paths, to highlight that they would be preemptible and to be >> wary if modifying or adding to them, but I opted not to in the end. >> (Partly as I didn't find a satisfactory way to do it !) >> I would be happy to add some if anyone finds it would be beneficial. > Tested-by: Luis Claudio R. Goncalves > > Works as advertised, fixes the reported RT problem, fails on the specific > case Ada described above. :) > > Best regards, > Luis > Thanks again Luis for the thorough testing and reports ! Best regards, Ada