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Thu, 01 Oct 2026 10:15:02 -0700 (PDT) Received: from jgg by wakko with local (Exim 4.97) (envelope-from ) id 1xCKN3-0000000EaHJ-0IkU; Thu, 01 Oct 2026 14:15:01 -0300 Date: Thu, 1 Oct 2026 14:15:01 -0300 From: Jason Gunthorpe To: David Woodhouse Cc: Fred Griffoul , Connor Williamson , ackerleytng@google.com, Hugh Dickins , Baolin Wang , Andrew Morton , Sean Christopherson , Paolo Bonzini , David Hildenbrand , Jonathan Corbet , Shuah Khan , Randy Dunlap , Shuah Khan , vannapurve@google.com, erdemaktas@google.com, jxgao@google.com, rientjes@google.com, fvdl@google.com, jthoughton@google.com, tarunsahu@google.com, pratyush@kernel.org, fuad.tabba@linux.dev, Gregory Price , yan.y.zhao@intel.com, michael.roth@amd.com, suzuki.poulose@arm.com, Christian Brauner , Nicolin Chen , Xu Yilun , aik@amd.com, aneesh.kumar@kernel.org, Vlastimil Babka , kernel-team@android.com, kernel-team@meta.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH RFC 01/17] mm: shmem: Implement guest_memfd provider operations for tmpfs Message-ID: <20261001171501.GD3019323@ziepe.ca> References: <20260925-gmem-tmpfs-backend-v1-0-d36159822d18@google.com> <20260925-gmem-tmpfs-backend-v1-1-d36159822d18@google.com> <9292b27b8f48c515bee3246cf3b3a60762302186.camel@infradead.org> <20261001141743.GB3019323@ziepe.ca> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Oct 01, 2026 at 04:47:54PM +0100, David Woodhouse wrote: > On Thu, 2026-10-01 at 11:17 -0300, Jason Gunthorpe wrote: > > It would be nice if it could handle MMIO and "cachable MMIO" as well. > > As opposed to just MMIO vs. RAM as implemented in the prototype in > https://git.infradead.org/?p=users/dwmw2/linux.git;a=commitdiff;h=a7ca2d8859036 ? Sort of, RAM is a little more permanent than "cachable mmio", I prefer the latter because it conveys it is located on a device, is subject to things like reset. Eg "CXL ram" would be cachable mmio. I haven't heard of anything needing a unique PTE for this yet, but who knows down the road. > I think Fred has a cleaner version of that about ready to post as the > next version of my series. Yeah, cleaned up is needed, I want us to resolve this in the dmabuf code cleanly not add more of the hack mess I made for vfio/iommufd.. Jason