From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2189220FABB; Thu, 12 Dec 2024 09:57:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733997428; cv=none; b=uwxDdbXDu1wsP4WAxUwXcxouOfuHigYD8juGWLV7tNHD32IMxw8UIcKqDYnv9zSbe3UYkHeOc7YfiYUT7Xk4pL71hoSVVVK0jMv8fRAL1HrYXF9JRWXd5kQSgKsbTZGhgkisIJLPAcYFiDFEwpjY4fu/VZ3zPIms7Yj3G+LW0N8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733997428; c=relaxed/simple; bh=CR4xKt3dKhiMF/jgSb/r1xl+RaNR7Vqb2fCQvyj4HNs=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=jVoM4RfIPfrf5NfVELbxbfXAwSvpbrvxcMECMKUQS715Ca/0T0WUg3OLR68IgfI/sNonpfjMBzbG68PKEjsmpGdZ/DQqPGmMYVzkbfBR3p+7m11ioX3qiwRomgLzx74JJ7IDS+Zpc7/3OYi4G96DtIuzFCz81DS7b4vGmFvawm8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dwisyUAO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dwisyUAO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ACE41C4CED7; Thu, 12 Dec 2024 09:57:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733997427; bh=CR4xKt3dKhiMF/jgSb/r1xl+RaNR7Vqb2fCQvyj4HNs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=dwisyUAO0Fe6OZk999b8H0f2W5l7v/tFtXoXFpH2iLDcjvQ2Jh+/cr/Oiikwk25Ea hpk9539OgJtSVYvyeBvqBs2mxR3IyU+Xxq1GUDel1LMdEN97lCrb2ACSNcJKnm0mjt HvxwR4/Pk9ZwAggD5eIZnVz/wezev9YpHja2gumgolOyK+UXqhefClt1oOAtPLbQfL POc3mTK8N7Vcvns+D9/ijUNSsiFPsvJWVehyFn/rY9+68WlRSXk2zy/Gqbq/dfimr1 b6AsgRZsKCsGOO3Lsq9ygPPrTIYm4IU9ibALKy4Fa6W+OXI5HB3ZJq1j4Z5A8NdIRh JV2EDm/s3lhvw== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1tLfwP-0031hu-H5; Thu, 12 Dec 2024 09:57:05 +0000 Date: Thu, 12 Dec 2024 09:57:05 +0000 Message-ID: <86msh1rzpq.wl-maz@kernel.org> From: Marc Zyngier To: Ryan Roberts Cc: =?UTF-8?B?TWlrb8WCYWo=?= Lenczewski , 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 1/5] arm64: Add TLB Conflict Abort Exception handler to KVM In-Reply-To: <5d4ccb2c-da45-4471-9bb1-90212b50dad7@arm.com> References: <20241211160218.41404-1-miko.lenczewski@arm.com> <20241211160218.41404-2-miko.lenczewski@arm.com> <86o71irucr.wl-maz@kernel.org> <5d4ccb2c-da45-4471-9bb1-90212b50dad7@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.4 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: ryan.roberts@arm.com, miko.lenczewski@arm.com, 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 X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Hi Ryan, On Thu, 12 Dec 2024 09:23:20 +0000, Ryan Roberts wrote: > > Hi Marc, > > I believe the intent of this patch is to protect the host/KVM against a guest > that is using BBML2. The host/KVM always assumes BBML0 and therefore doesn't do > any operations that are allowed by the arch to cause a conflict abort. Therefore > the host doesn't need to handle it. But a guest could be taking advantage of > BBML2 and therefore it's architiecturally possible for a conflict abort to be > raised to EL2. I think today that would take down the host? > > So really I think this could be considered a stand-alone KVM > hardening improvement? I'm not disputing the need for a TLB Conflict abort handler. It will be a good addition once we agree on what needs to be done. > > However, it doesn't seem to me that the host is equipped to deal with > > this sort of exception for itself. Shouldn't you start with that? > > If the host isn't doing any BBML2 operations it doesn't need to handle it, I > don't think? Obviously that changes later in the series and Miko is adding the > required handling to the host. Yes, and that's what I overlooked yesterday, and I replied to that change this morning. Thanks, M. -- Without deviation from the norm, progress is not possible.