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Thu, 10 Sep 2026 15:42:36 -0700 (PDT) Date: Thu, 10 Sep 2026 15:42:36 -0700 In-Reply-To: <20260910221832.GH3968357@nvidia.com> Mime-Version: 1.0 References: <20260903023452.721732-1-loganodell@google.com> <20260904160009.GV4157646@nvidia.com> <20260905012403.GX4157646@nvidia.com> <20260910143448.GD3968357@nvidia.com> <20260910171210.GF3968357@nvidia.com> <20260910221832.GH3968357@nvidia.com> Message-ID: Subject: Re: [RFC PATCH 0/3] liveupdate: Move to feature flags for LUO and memfd ABI compatibility From: Sean Christopherson To: Jason Gunthorpe Cc: David Matlack , Logan Odell , arnd@arndb.de, pasha.tatashin@soleen.com, rppt@kernel.org, pratyush@kernel.org, graf@amazon.com, akpm@linux-foundation.org, pbonzini@redhat.com, maz@kernel.org, oupton@kernel.org, bhelgaas@google.com, alex@shazbot.org, kevin.tian@intel.com, dwmw2@infradead.org, baolu.lu@linux.intel.com, joro@8bytes.org, will@kernel.org, robin.murphy@arm.com, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-pci@vger.kernel.org, iommu@lists.linux.dev Content-Type: text/plain; charset="us-ascii" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260910_154238_905388_1DE06670 X-CRM114-Status: UNSURE ( 7.87 ) X-CRM114-Notice: Please train this message. X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On Thu, Sep 10, 2026, Jason Gunthorpe wrote: > Sean's initial email was asking for strict never-break ABI compatability > rules on top, and that is what I've been reacting to. No, I was never asking for that. I think we just have a different interpretation of ABI, or rather are talking about different pieces of ABI. I am still asking for never-break serialization format compatibility, i.e. the more literal save/restore ABI. I'm not asking for full backwards/forwards compatibility across all kernels version, i.e. the higher level "kernel" ABI. To phrase things differently: I am a-ok if kernels are inherently incompatible because they fundamentally operate differently and/or support different features. I am not ok if we end up with incompatible kernels because the save/restore interfaces and payloads are poorly designed, lack abstraction, etc.