From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean-Philippe Brucker Subject: Re: [PATCH] vfio/iommu_type1: report the IOMMU aperture info Date: Thu, 30 Nov 2017 12:57:56 +0000 Message-ID: <1ad1aff9-1651-d1a9-cd1b-07bfd7dd0817@arm.com> References: <1512041678-4563-1-git-send-email-pmorel@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit 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" To: Pierre Morel , "alex.williamson@redhat.com" Return-path: In-Reply-To: <1512041678-4563-1-git-send-email-pmorel@linux.vnet.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.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