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[156.34.48.30]) by smtp.gmail.com with ESMTPSA id y66sm769077qka.24.2020.05.19.17.20.56 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 19 May 2020 17:20:56 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1jbCTf-0003SK-R4; Tue, 19 May 2020 21:20:55 -0300 Date: Tue, 19 May 2020 21:20:55 -0300 From: Jason Gunthorpe To: Alex Williamson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cohuck@redhat.com, peterx@redhat.com Subject: Re: [PATCH 2/2] vfio: Introduce strict PFNMAP mappings Message-ID: <20200520002055.GC31189@ziepe.ca> References: <158947414729.12590.4345248265094886807.stgit@gimli.home> <158947512947.12590.4756232870747830161.stgit@gimli.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <158947512947.12590.4756232870747830161.stgit@gimli.home> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 14, 2020 at 10:52:09AM -0600, Alex Williamson wrote: > vfio_unregister_iommu_driver(&vfio_noiommu_ops); > diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > index 62ba6bd8a486..8d6286d89230 100644 > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -61,6 +61,11 @@ module_param_named(dma_entry_limit, dma_entry_limit, uint, 0644); > MODULE_PARM_DESC(dma_entry_limit, > "Maximum number of user DMA mappings per container (65535)."); > > +static bool strict_mmio_maps = true; > +module_param_named(strict_mmio_maps, strict_mmio_maps, bool, 0644); > +MODULE_PARM_DESC(strict_mmio_maps, > + "Restrict DMA mappings of MMIO to those provided by vfio bus drivers supporting invalidation (true)."); > + This should probably explain that 'false' allows some kind of security issue and maybe taint the kernel? Do you think there is a reason to have this anyhow? Jason