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 10DFBCA5FCB for ; Thu, 1 Oct 2026 11:32:40 +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:In-Reply-To: Content-Transfer-Encoding:Content-Type: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=hW1lFRhTfd1XvPXBZZ4fZBn5mUdcZRR29Siru0Ej7Fc=; b=y6GbgXM1Toeo5XFVNUiiP5CzNq wfyP+rv5gqzKwYH8sDH071C+NoC7M0jBqkJ2bWB2oogFp02mVEz8FyjT2SLTUxnx7EuCOy0Ok6l3/ aQ6cYpYqpDt8O1E5V2Q4sbxcB+WOs216WL92j7+uUn+afJca4imQmMisc8fpYZAaLpQHJsNJQywo8 Umy/hmYhNvkhM55z7lzxteRhBjEbERlbflY/9dnVI30bVJyf7S4CquPtx3PYODVh9thENOLx8U98U JMENaOn+H4q1pv8tQr/ZMTu1txhvHtO9P8o8h1xtUWWES7KfBGROwSo8Guy7JvvDPtjfGxYLAIc8o yNNMNOzg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xCF1c-00000008doF-43LG; Thu, 01 Oct 2026 11:32:32 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xCF1b-00000008do7-0U9l for linux-arm-kernel@lists.infradead.org; Thu, 01 Oct 2026 11:32:31 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 7396E60A55; Thu, 1 Oct 2026 11:32:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 870341F000FF; Thu, 1 Oct 2026 11:32:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790854350; bh=hW1lFRhTfd1XvPXBZZ4fZBn5mUdcZRR29Siru0Ej7Fc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=j8lQaessvpy0Sge3/FTK04t5fXsU9wMJx20b79fxBhSvAoPBddsGQ3hHEtwLIkT8m u9z33Vn2IkVC0mgn8cYj87xL8LC57fITgnHCA3D2VPwiiqYBrWAfaxMHAWAeG1+xY3 /Izp8FJBIV0XXc9MYdrIBi3YZOQzPOAGaWL6lgpAJy7ei4msBLXrwu/9B9xcXEd/JS 8DO1mG6E2/IycQa7gfpzr3tjsv6S96JYLuLRhE0ENkMy5GiGp2G/zEqDNtPNYqQPTK ZREKjyVJfzzhlxPKBKy31zJZL0gUd/rCtw06Zl9obkUbYK+z2o8iItqw2JBiO+uswr oNzN1ZYO8yWrw== Date: Thu, 1 Oct 2026 12:32:23 +0100 From: Will Deacon To: Linus Walleij Subject: Re: [PATCH v2 19/21] arm64: entry: The great stack switcheroo Message-ID: References: <20260918161407.2300-1-will@kernel.org> <20260918161407.2300-20-will@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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 , Vladimir Murzin , Arnd Bergmann , Catalin Marinas , linux-kernel@vger.kernel.org, Mostafa Saleh , Marc Zyngier , David Hildenbrand , Lorenzo Stoakes , Oliver Upton , Ard Biesheuvel , 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 Thu, Oct 01, 2026 at 10:38:22AM +0200, Linus Walleij wrote: > On Thu, Oct 1, 2026 at 9:27 AM Will Deacon wrote: > > On Wed, Sep 30, 2026 at 11:36:35PM +0200, Linus Walleij wrote: > > > On Fri, Sep 18, 2026 at 6:15 PM Will Deacon wrote: > > > > > > > With the kernel stack pointer in SP_EL1 and the overflow stack pointer > > > > in SP_EL0, it is now straightforward to switch between the two on > > > > exception entry from EL1 by writing to SPSel. However, since exception > > > > entry sets PSTATE.SP to 1 (selecting SP_EL1 as the stack pointer), > > > > repurposing the overflow stack as a more general kernel exception stack > > > > would require writing to SPSel on every exception entry from the kernel. > > > > > > > > Switch things around so that the overflow stack resides in SP_EL1, with > > > > the kernel stack residing in SP_EL0. > > > > > > > > Signed-off-by: Will Deacon > > > > > > This patch gives me panic, and as can be seen from the review > > > comments need some love... > > > > Please can you share the panic message? I'll definitely be reworking > > this based on the review comments, but if there's a bug it would be > > great to see the details now! > > Haha. I was not referring to the kernel function but the emotion ;D Oh! That kind of panic is easier to fix :) Are you going to LPC? Will