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Thu, 01 Oct 2026 10:15:02 -0700 (PDT) Received: from ziepe.ca ([130.41.10.202]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-6dd97aff835sm3239083eaf.6.2026.10.01.10.15.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Stat-Signature: y1ojx84zxpfax7qp7ozfgh3e6ggoq19h X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 28337140005 X-HE-Tag: 1790874904-144011 X-HE-Meta: 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 2Rz9kVPm 3EYGRMLRrsauOO6VFtE5vPNEjg2ewF8q9upoItY5BrodiBFK+TseOf3JM75MEFE113ZB3TZrv3nx+lnPLmkZ+yTiKt4GSX1mmX94dNyEXm+YAb4yDM816d6kk0pdHqfcK4KmdXmBBLup9TJ6f49GnkPVh/8ZKW2a09u5lGEEhmUPpMZTyvYa5JpX4YWHpc+68SYZJW+IOybptv6Xxpe/xGX0xrxFzSutVJOOZ4zzyL9tlNyTONtR+MwnePkUAcPMBRbd+92UUHyQHhoGoqs3jdAtlmPwXBQS4d/wrEQGhqC3m9tGqrwMoscv5DPQiS4R2ENSHo0gIshOvghvkBddyr+8cnXPXWNfTUAH9rsj5DjIhR/3jiza7N2BTjpo6eTS57esQbf+oOlyagRg= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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