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Wed, 29 Apr 2026 16:58:52 -0700 (PDT) Date: Thu, 30 Apr 2026 00:58:50 +0100 From: Gregory Price To: Ira Weiny Cc: Dave Jiang , linux-cxl@vger.kernel.org, nvdimm@lists.linux.dev, djbw@kernel.org, iweiny@kernel.org, pasha.tatashin@soleen.com, mclapinski@google.com, rppt@kernel.org, joao.m.martins@oracle.com, jic23@kernel.org, john@groves.net, rick.p.edgecombe@intel.com Subject: Re: [RFC PATCH 00/12] dax: Add DAX to guest memfd support for KVM Message-ID: References: <20260423170219.281618-1-dave.jiang@intel.com> <69f205bc6402_3a7a81004d@xwing.notmuch> Precedence: bulk X-Mailing-List: linux-cxl@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: <69f205bc6402_3a7a81004d@xwing.notmuch> On Wed, Apr 29, 2026 at 08:21:00AM -0500, Ira Weiny wrote: > Gregory Price wrote: I think we're largely in agreement here, so trimming a bunch of this. > > > > The question is ultimately how much flexibility you need to shuffle this > > capacity from one guest to another. > > Yep. And how much control one needs over which exact CXL/DAX devices the > memory comes from. As you know from our community calls that is one thing > I'm not sure the private node idea is great at. But it could be that is > not really required. Or is best handled as a carve out. > If you can do Device<->Node mappings, then this is trivial. If you need more specific handling, then private nodes are not the way. The intent of private nodes is to make mmap()/malloc() etc functional in a heterogenous memory world, which is explicitly different than "give me a specific chunk of physical capacity". Which, tl;dr: "There's a real argument for just handing guest_memfd a chunk of unmapped memory and making it deal with the problem". (shared gmem is... odd... given the original intent not do this :P) ~Gregory