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Wed, 04 Nov 2026 04:29:44 -0800 (PST) Message-ID: Date: Wed, 4 Nov 2026 13:29:43 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/2] memblock: keep reserve_mem regions out of KHO bootmem To: Pratyush Yadav Cc: Mike Rapoport , Andrew Morton , Kees Cook , Alexander Graf , Changyuan Lyu , Tony Luck , "Guilherme G. Piccoli" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Pasha Tatashin , kexec@lists.infradead.org References: <20261021211058.83483-1-azpijr@gmail.com> <2vxzqzhhg8l3.fsf@kernel.org> <32dd1f28-db55-4674-99bc-74d9d3ab25db@gmail.com> <70686061-787c-4c99-ba5b-ff982c8cc2ad@gmail.com> <2vxzfqxglrg6.fsf@kernel.org> Content-Language: en-US From: "Jose A. 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Perez de Azpillaga wrote: > >> On 10/22/26 10:16 PM, Jose A. Perez de Azpillaga wrote: >>> On 10/22/26 3:37 PM, Pratyush Yadav wrote: >>>> On Wed, Oct 21 2026, Jose A. Perez de Azpillaga wrote: >>>> >>>>> On a KHO boot, a reserve_mem= region that can't be revived (new name, >>>>> size or alignment) can be allocated from KHO bootmem, which the next >>>>> kernel boots out of. With CONFIG_KEXEC_HANDOVER_DEBUG preserving it >>>>> fails; without it, the next kernel's memmap ends up on top of it. >>>> What's your use-case? Why are you adding new reserve_mem regions after >>>> cold boot? I'd rather avoid making purely theoretical fixes. >>> >>> I don't have one, I found it through the TODO. a different reserve_mem= >>> in the cmdline passed to kexec is enough to hit it. > > If there was a use case, I wouldn't mind fixing it. But I'd rather not > add code we don't have a use case for. > >>> >>> if it isn't meant to work across a live update, would you rather have >>> reserve_mem() fail on KHO boot when it can't revive the region? > > This sounds good I think. > okay, I'll drop 1/2 and send that as v2 :) -- cheers, jose a. p-a From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9B5D9606A326 for ; Wed, 4 Nov 2026 12:29:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=3/gfTs2g; dkim=fail reason="signature verification failed" (2048-bit key, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=rzu3Yuuf DKIM-Signature: v=1; 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Wed, 04 Nov 2026 04:29:44 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b2aae24b32sm129017035e9.12.2026.11.04.04.29.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Nov 2026 04:29:44 -0800 (PST) Message-ID: Date: Wed, 4 Nov 2026 13:29:43 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 0/2] memblock: keep reserve_mem regions out of KHO bootmem To: Pratyush Yadav References: <20261021211058.83483-1-azpijr@gmail.com> <2vxzqzhhg8l3.fsf@kernel.org> <32dd1f28-db55-4674-99bc-74d9d3ab25db@gmail.com> <70686061-787c-4c99-ba5b-ff982c8cc2ad@gmail.com> <2vxzfqxglrg6.fsf@kernel.org> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <2vxzfqxglrg6.fsf@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261104_042951_523983_9B963766 X-CRM114-Status: GOOD ( 14.43 ) X-Spam-Score: -2.1 (--) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Tony Luck , Pasha Tatashin , linux-mm@kvack.org, Kees Cook , Changyuan Lyu , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Alexander Graf , Andrew Morton , Mike Rapoport Sender: "kexec" X-Spam-Status: No, score=-2.3 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 11/4/26 1:19 PM, Pratyush Yadav wrote: > On Wed, Nov 04 2026, Jose A. Perez de Azpillaga wrote: > >> On 10/22/26 10:16 PM, Jose A. Perez de Azpillaga wrote: >>> On 10/22/26 3:37 PM, Pratyush Yadav wrote: >>>> On Wed, Oct 21 2026, Jose A. Perez de Azpillaga wrote: >>>> >>>>> On a KHO boot, a reserve_mem= region that can't be revived (new name, >>>>> size or alignment) can be allocated from KHO bootmem, which the next >>>>> kernel boots out of. With CONFIG_KEXEC_HANDOVER_DEBUG preserving it >>>>> fails; without it, the next kernel's memmap ends up on top of it. >>>> What's your use-case? Why are you adding new reserve_mem regions after >>>> cold boot? I'd rather avoid making purely theoretical fixes. >>> >>> I don't have one, I found it through the TODO. a different reserve_mem= >>> in the cmdline passed to kexec is enough to hit it. > > If there was a use case, I wouldn't mind fixing it. But I'd rather not > add code we don't have a use case for. > >>> >>> if it isn't meant to work across a live update, would you rather have >>> reserve_mem() fail on KHO boot when it can't revive the region? > > This sounds good I think. > okay, I'll drop 1/2 and send that as v2 :) -- cheers, jose a. p-a