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b=DTci9JOWIGHKfBoQb3CBfSV1SkaFony1B9cQxR/582XmSaBE0WcAVXehCunpqUihN FcSL9fchO9EriU8hNo2GAlseP1MoOnrrdV/AyxTRDEq1Ol5ptedub8IwkszrzuqoEY swWIWr9i1t5L/RQDig18MQO15ZxE+C2JBWaEWTU4bG25OzyCJ51zbowDDHd3UFF5XE f3PMBjDE+iF6kT+TtVb99M0QRkFKJaZDrOEDpLo7xKZuZMAIMY60GLDzL1TodfoyH4 Wv9HTOujAGR4LZKtOqXySgP/XHA8H65aLq/KqyUT0ASQ0/EqW7VhIL1rPzLeQcwxQS uTq86OLThc6Rg== Date: Thu, 9 Jul 2026 11:26:08 +0100 From: Sudeep Holla To: Shyam Saini Cc: Catalin Marinas , Sudeep Holla , Mike Rapoport , ardb@kernel.org, david@kernel.org, will@kernel.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, bboscaccy@linux.microsoft.com, bp@alien8.de, dapeng1.mi@linux.intel.com, ebiggers@kernel.org, elver@google.com, enelsonmoore@gmail.com, feng.tang@linux.alibaba.com, gpiccoli@igalia.com, kees@kernel.org, kuba@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lirongqing@baidu.com, peterz@infradead.org, rdunlap@infradead.org, tgopinath@linux.microsoft.com, tony.luck@intel.com, Lorenzo Pieralisi , Hanjun Guo Subject: Re: [RFC v2 PATCH] reserve_mem: add support for static memory Message-ID: <20260709-educational-nimble-seagull-5fc031@sudeepholla> References: <20260630170911.43521-1-shyamsaini@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 161CD180004 X-Stat-Signature: 4if1b76nqj68q9o7zafkhdjqwdw39oas X-HE-Tag: 1783592775-983315 X-HE-Meta: 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 Gvz40wXx CSparxH2qE2JoCQ9e2i8eFUo9zeJ8QKvZD2ssZTCRdrNbDCTs27onBMjfncfvwXfVChWF6CCEdykXMeigIwN/8hTdSVXzYYx8A2dceR7/7fOb8oTrxV3g0lpQepi2XdVoffUHxGNfEKPLF/vxGv0hzxjNAm2ZIDbOn863iilKY5DPqVLNP/7PKvx1Lu26jlSe90IZPIFs4q4tjJySXAFdP9dFzKNBE5MExqj1MtlfHdHHYmMdgWBFcQU2+UGO7QxetrCFOrn8DK62IzIuUKASD4YScUtXKtRA0NE4x4DGIcSjtGY= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jul 08, 2026 at 05:37:33PM -0700, Shyam Saini wrote: > Hi Catalin, > > On 08 Jul 2026 11:00, Catalin Marinas wrote: > > Hi Shyam, > > > > Adding Lorenzo, Hanjun, Sudeep. > > > > On Tue, Jun 30, 2026 at 10:09:11AM -0700, Shyam Saini wrote: > > > Following up on this, As Mike pointed that reserve_mem is best effort > > > reservation mechanism, so what is the recommended reliable Linux > > > mechanism, if any, to reserve a predetermined memory range during > > > early boot on ARM64/ACPI platforms for warm boot scenarios? KHO is > > > one option, but I'm specifically looking for a solution that preserves > > > the region across warm reboots. > > > > If you need ramoops-like support, I think ACPI ERST is a better fit and > > we don't need any memory reservation tricks. I'll let the arm ACPI > > maintainers comment further. > > > > while this patch mentions use case of ramoops, there are other uses cases that > requires predetermined memory reservation at boot time, one of them is PMEM. > Like Mike pointed out in this [1] thread, we don't seem to have an > equivalent mechanism for reserving predetermined memory on ARM/ACPI > platforms, as is available on ARM/DTS based platforms. > Indeed, it was been discussed in several forums in the past but AFAIK there is no conclusion or a direction towards solving this yet. -- Regards, Sudeep