From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id A7FE4204C28; Thu, 12 Dec 2024 10:37:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733999854; cv=none; b=GQ9sgw1FZuBuKV4utl1NGoApnjrY5Ldhv/BJkKinWMnwAeeyq5VhYkHpJAR/+c/89e3vkZz1e2qlMNxaYePcNIxGMddCKKgbpzaBXn3lXPyggL4tk9hwiZq+fo9tR1aoJH9ObLLYIIosS+kZxONQXJgxnRLXJ3VJV5uo9taoALM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733999854; c=relaxed/simple; bh=yy/4XN030xD33beCc1FfwV0Weof0Er6ZiG6oMzwCIWA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=G7dYJbDJkgzGzIJVgdSlU8D5tB7ndIYjzq0rzmCzRNa7Z5iTsvvt6XC6LywZBzDPOcADP4nNUgGUlDMunQLlQcRj2K9aCoGsl5BQ91fJXO96m1sGR5tC8DZMxyVttvyujpagcF48dWisxMQ++IVMZjcTm8FtHWfxW9GVYf5HMzs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 F35C0169E; Thu, 12 Dec 2024 02:37:59 -0800 (PST) Received: from [10.57.92.2] (unknown [10.57.92.2]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 77FB63F58B; Thu, 12 Dec 2024 02:37:29 -0800 (PST) Message-ID: <342b9c16-690d-42ed-a6f4-bb3972193a8f@arm.com> Date: Thu, 12 Dec 2024 10:37:27 +0000 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RESEND RFC PATCH v1 1/5] arm64: Add TLB Conflict Abort Exception handler to KVM Content-Language: en-GB To: Marc Zyngier Cc: =?UTF-8?Q?Miko=C5=82aj_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 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> <86msh1rzpq.wl-maz@kernel.org> From: Ryan Roberts In-Reply-To: <86msh1rzpq.wl-maz@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12/12/2024 09:57, Marc Zyngier wrote: > 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. OK great, glad we are on the same page. I'll leave Miko to work through the details. > >>> 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. >