From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752835AbdK3Myq (ORCPT ); Thu, 30 Nov 2017 07:54:46 -0500 Received: from foss.arm.com ([217.140.101.70]:52058 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752359AbdK3Myo (ORCPT ); Thu, 30 Nov 2017 07:54:44 -0500 Subject: Re: [PATCH] vfio/iommu_type1: report the IOMMU aperture info To: Pierre Morel , "alex.williamson@redhat.com" Cc: "cohuck@redhat.com" , "borntraeger@de.ibm.com" , "zyimin@linux.vnet.ibm.com" , "pasic@linux.vnet.ibm.com" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" References: <1512041678-4563-1-git-send-email-pmorel@linux.vnet.ibm.com> From: Jean-Philippe Brucker Message-ID: <1ad1aff9-1651-d1a9-cd1b-07bfd7dd0817@arm.com> Date: Thu, 30 Nov 2017 12:57:56 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <1512041678-4563-1-git-send-email-pmorel@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On 30/11/17 11:34, Pierre Morel wrote: [...] > +/** > + * vfio_get_aperture - report minimal aperture of a vfio_iommu > + * @iommu: the current vfio_iommu > + * @start: a pointer to the aperture start > + * @end : a pointer to the aperture end > + * > + * This function iterate on the domains using the given vfio_iommu > + * and restrict the aperture to the minimal aperture common > + * to all domains sharing this vfio_iommu. > + */ > +static void vfio_get_aperture(struct vfio_iommu *iommu, uint64_t *start, > + uint64_t *end) > +{ > + struct iommu_domain_geometry geometry; > + struct vfio_domain *domain; > + > + *start = 0; > + *end = U64_MAX; I wonder if the default values should also reflect what the VFIO implementation actually supports. Looking at vfio_dma_do_map, a 32-bit host will reject any iova greater than 32 bits. In addition, vfio_dma_do_unmap doesn't support unmapping the last page of a 64-bit address space (existing IOMMUs would probably reject map requests with IOVA > 52 bits anyway, but if they don't report a domain aperture, VFIO can't guess it). I think it's convenient to use VFIO_IOMMU_UNMAP_DMA on the full address space when an unmap-all is needed, maybe we could provide default aperture values that help doing this? (~0U for 32-bit and (~0ULL - PAGE_SIZE) for 64-bit) Thanks, Jean