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Sun, 04 Oct 2026 08:09:03 -0700 (PDT) X-Received: by 2002:a05:600c:4453:b0:4a0:2423:946 with SMTP id 5b1f17b1804b1-4a1680f109emr87154015e9.15.1791126543248; Sun, 04 Oct 2026 08:09:03 -0700 (PDT) Received: from px13 ([2a06:5902:822:4600:8c2f:7cc8:bd95:9422]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a027727cecsm272425775e9.9.2026.10.04.08.09.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 04 Oct 2026 08:09:02 -0700 (PDT) Date: Sun, 4 Oct 2026 16:09:00 +0100 From: Chris Bainbridge To: Pratyush Yadav Cc: Mike Rapoport , Pasha Tatashin , Jason Miu , Alexander Graf , Ran Xiaokai , regressions@lists.linux.dev, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, =?utf-8?B?TWljaGHFgiBDxYJhcGnFhHNraQ==?= Subject: Re: [BUG] KHO handover hangs when memmap reserves PMEM Message-ID: References: <2vxzcxtplh4i.fsf@kernel.org> 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: <2vxzcxtplh4i.fsf@kernel.org> On Sun, Oct 04, 2026 at 03:39:25PM +0200, Pratyush Yadav wrote: > > Just to confirm, the first kernel boots without memmap= right? Yes. > I think the main problem is that the radix tree pages can be anywhere in > memory. So on the first kernel, they can land in an area that the second > kernel's memmap= reserves. So kho_memory_init() might end up using > memory that memmap= reserved. I'm not sure why exactly the next kernel > doesn't produce any output, but IIRC memmap= memory is not mapped to the > direct map, so accessing those pages likely causes a page fault. That's correct, kho_memory_init() page faults. It happens before the serial console is available, so there is no output.