From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 1/3] swiotlb: Export maximum allocation size Date: Mon, 14 Jan 2019 16:59:27 -0500 Message-ID: <20190114165800-mutt-send-email-mst@kernel.org> References: <20190110134433.15672-1-joro@8bytes.org> <20190110134433.15672-2-joro@8bytes.org> <20190110170205.GB27546@char.us.oracle.com> <20190111091231.GB5825@8bytes.org> <20190114204907.GH32038@char.us.oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190114204907.GH32038@char.us.oracle.com> Sender: linux-kernel-owner@vger.kernel.org To: Konrad Rzeszutek Wilk Cc: Joerg Roedel , Jason Wang , Jens Axboe , virtualization@lists.linux-foundation.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, jfehlig@suse.com, jon.grimm@amd.com, brijesh.singh@amd.com, hch@lst.de, Joerg Roedel List-Id: iommu@lists.linux-foundation.org On Mon, Jan 14, 2019 at 03:49:07PM -0500, Konrad Rzeszutek Wilk wrote: > On Fri, Jan 11, 2019 at 10:12:31AM +0100, Joerg Roedel wrote: > > On Thu, Jan 10, 2019 at 12:02:05PM -0500, Konrad Rzeszutek Wilk wrote: > > > Why not use swiotlb_nr_tbl ? That is how drivers/gpu/drm use to figure if they > > > need to limit the size of pages. > > > > That function just exports the overall size of the swiotlb aperture, no? > > What I need here is the maximum size for a single mapping. > > Yes. The other drivers just assumed that if there is SWIOTLB they would use > the smaller size by default (as in they knew the limitation). > > But I agree it would be better to have something smarter - and also convert the > DRM drivers to piggy back on this. > > Or alternatively we could make SWIOTLB handle bigger sizes.. Just a thought: is it a good idea to teach blk_queue_max_segment_size to get the dma size? This will help us find other devices possibly missing this check. > > > > Regards, > > > > Joerg