Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 29 Sep 2020 07:03:07 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Eric Auger <eric.auger@redhat.com>
Cc:     eric.auger.pro@gmail.com, joro@8bytes.org,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        will.deacon@arm.com, robin.murphy@arm.com, dwmw2@infradead.org,
        alex.williamson@redhat.com, jean-philippe.brucker@arm.com
Subject: Re: [RFC 2/3] iommu: Account for dma_mask and iommu aperture in IOVA
 reserved regions
Message-ID: <20200929060307.GA6564@infradead.org>
References: <20200928195037.22654-1-eric.auger@redhat.com>
 <20200928195037.22654-3-eric.auger@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200928195037.22654-3-eric.auger@redhat.com>
Precedence: bulk

On Mon, Sep 28, 2020 at 09:50:36PM +0200, Eric Auger wrote:
> VFIO currently exposes the usable IOVA regions through the
> VFIO_IOMMU_GET_INFO ioctl. However it fails to take into account
> the dma_mask of the devices within the container. The top limit
> currently is defined by the iommu aperture.

Can we take a step back here?  The dma_mask only has a meaning for
the DMA API, and not the iommu API, it should have no relevance here.

More importantly if we are using vfio no dma_mask should be set to
start with.

> +		if (geo.aperture_end < ULLONG_MAX && geo.aperture_end != geo.aperture_start) {

Please avoid pointlessly overlong lines.