From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Date: Sat, 21 Mar 2020 08:20:41 +0000 Subject: Re: [PATCH 3/4] mm: simplify device private page handling in hmm_range_fault Message-Id: <20200321082041.GA28613@lst.de> List-Id: References: <7256f88d-809e-4aba-3c46-a223bd8cc521@nvidia.com> <20200317121536.GQ20941@ziepe.ca> <20200317122445.GA11662@lst.de> <20200317122813.GA11866@lst.de> <20200317124755.GR20941@ziepe.ca> <20200317125955.GA12847@lst.de> <24fca825-3b0f-188f-bcf2-fadcf3a9f05a@nvidia.com> <20200319181716.GK20941@ziepe.ca> <89e33770-a0ab-e1ec-d5e5-535edefd3fd3@nvidia.com> <20200320000345.GO20941@ziepe.ca> In-Reply-To: <20200320000345.GO20941@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Jason Gunthorpe Cc: Ralph Campbell , Christoph Hellwig , Dan Williams , Bharata B Rao , Christian =?iso-8859-1?Q?K=F6nig?= , Ben Skeggs , Jerome Glisse , kvm-ppc@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org On Thu, Mar 19, 2020 at 09:03:45PM -0300, Jason Gunthorpe wrote: > > Should tests enable the feature or the feature enable the test? > > IMHO, if the feature is being compiled into the kernel, that should > > enable the menu item for the test. If the feature isn't selected, > > no need to test it :-) > > I ment if DEVICE_PRIVATE should be a user selectable option at all, or > should it be turned on when a driver like nouveau is selected. I don't think it should be user selectable. This is an implementation detail users can't know about. > Is there some downside to enabling DEVICE_PRIVATE? The option itself adds a little more code to the core kernel, and introduces a few additional branches in core mm code. But more importantly it pulls in the whole pgmap infrastructure.