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 8213AE7717F for ; Fri, 13 Dec 2024 16:56:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: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: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=MeRRGLDDb0ux1182zAHVdE8lHrLfJb7fiMK9nZBfy2I=; b=V4gFMVdIw2ZqzgzEjGssiAW3rR 4jwZjuZ/3JupgnAxm51/R9GzW38WC4MgA1+5YVsxCC1sB1vK+KC34sLMC01DBNNds0sHMMVx2PBCl HGD6t19rVA9Pav+H5c/k5FEsdB3A/vt0dTCjbBVnTF7XY+LRfLYho9nnVWjLbMtiKuSYtbliHqxGC nhZnzkHgRygNjW6MrDmycRmZGmzzH/iZ3kk6+PG1whnZHLsZFsJs6WCMgNFWYUlpT017XaoVF3fJ6 qnnGrKAG6+OU+72PXb2wNbTkwGjI1Eo6ebRo/BJzTIbkFD7MUN+5X8xNVSl1RvLfV9fqbV0UZ57Jw 9VrdXnGQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tM8xS-00000004UtA-2lvp; Fri, 13 Dec 2024 16:56:06 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tM8ui-00000004UB2-20TQ for linux-arm-kernel@lists.infradead.org; Fri, 13 Dec 2024 16:53:17 +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 C9E841480; Fri, 13 Dec 2024 08:53:41 -0800 (PST) Received: from mazurka.cambridge.arm.com (mazurka.cambridge.arm.com [10.1.196.66]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C20F33F5A1; Fri, 13 Dec 2024 08:53:11 -0800 (PST) Date: Fri, 13 Dec 2024 16:53:09 +0000 From: =?utf-8?Q?Miko=C5=82aj?= Lenczewski To: Marc Zyngier Cc: Ryan Roberts , catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev Subject: Re: [RESEND RFC PATCH v1 2/5] arm64: Add BBM Level 2 cpu feature Message-ID: <20241213165309.GE30314@mazurka.cambridge.arm.com> References: <20241211160218.41404-1-miko.lenczewski@arm.com> <20241211160218.41404-3-miko.lenczewski@arm.com> <87cyhxs3xq.wl-maz@kernel.org> <084c5ada-51af-4c1a-b50a-4401e62ddbd6@arm.com> <86ikrprn7w.wl-maz@kernel.org> <2b1cc228-a8d5-4383-ab25-abbbcccd2e2c@arm.com> <86h678sy00.wl-maz@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <86h678sy00.wl-maz@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241213_085316_558726_08718500 X-CRM114-Status: GOOD ( 21.74 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org > > > > From the ARM: > > """ > > RFCPSG: If level 1 or level 2 is supported and the Contiguous bit in a set of > > Block descriptors or Page descriptors is changed, then a TLB conflict abort can > > be generated because multiple translation table entries might exist within a TLB > > that translates the same IA. > > """ > > > > Although I guess it's not totally explicit, I've interpretted that as saying > > that conflicting TLB entries can only arise for the IA range for which the > > contiguous bits have been modified in the translation tables. > > Right, that's reassuring, thanks for digging that one. > Thanks Ryan, will improve the comment and commit messages to make this clearer and to include references to this information. > > > If anything, this should absolutely check for FAR_EL1 and assert that > > > this is indeed caused by such change. > > > > I'm not really sure how we would check this reliably? Without patch 5, the > > problem is somewhat constrained; we could have as many changes in flight as > > there are CPUs so we could keep a list of all the {mm_struct, VA-range} that are > > being modified. But if patch 5 is confirmed to be architecturally sound, then > > there is no "terminating tlbi" so there is no bound on the set of {mm_struct, > > VA-range}'s that could legitimately cause a conflict abort. > > I didn't mean to imply that we should identify the exact cause of the > abort. I was hoping to simply check that FAR_EL1 reports a userspace > VA. Why wouldn't that work? > Will do so. Kind regards, MikoĊ‚aj