From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752730AbdGLRy4 (ORCPT ); Wed, 12 Jul 2017 13:54:56 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:57464 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752617AbdGLRyy (ORCPT ); Wed, 12 Jul 2017 13:54:54 -0400 Date: Wed, 12 Jul 2017 18:54:56 +0100 From: Will Deacon To: Eric Auger Cc: eric.auger.pro@gmail.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, robin.murphy@arm.com, Jean-Philippe.Brucker@arm.com, christoffer.dall@linaro.org, Marc.Zyngier@arm.com, alex.williamson@redhat.com, peterx@redhat.com, mst@redhat.com Subject: Re: [RFC 0/2] arm-smmu-v3 tlbi-on-map option Message-ID: <20170712175454.GF15191@arm.com> References: <1499613303-30173-1-git-send-email-eric.auger@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1499613303-30173-1-git-send-email-eric.auger@redhat.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Eric, On Sun, Jul 09, 2017 at 05:15:01PM +0200, Eric Auger wrote: > This series adds a new tlbi-on-map option to the smmuv3 driver. > When set, the IO_PGTABLE_QUIRK_TLBI_ON_MAP quirk is applied for > LPAE tables and the smmuv3 driver sends TLB invalidations on map. > > This mode is useful when running the driver on a guest as it allows > the virtualizer to trap any change to the translation structures. > This is similar to the Intel vtd caching mode (CM). > > This is especially needed for VFIO integration integration where > guest mappings must be applied to the physical IOMMU. > > At the moment the option only is available for DT probing. I'm really not a fan of this approach. If a virtual IOMMU implementation is advertising itself as an SMMUv3, then it should adhere to the SMMUv3 architecture and not require non-standard behaviour from the driver. If we're going to allow that, then we're better off going the extra mile and using a PV approach. Given that the the SMMU3 architecture does *not* require TLBI on map, then I don't think we should be quirking our behaviour in this way. The fact that you only have this implemented for DT is the canary in the coal mine imo. Will