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Thu, 05 Nov 2026 03:56:26 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fea181085sm9708651f8f.1.2026.11.05.03.56.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Nov 2026 03:56:26 -0800 (PST) Message-ID: Date: Thu, 5 Nov 2026 12:56:24 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] memblock: don't allocate new reserve_mem regions on a KHO boot To: Mike Rapoport References: <20261104204235.9066-1-azpijr@gmail.com> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: 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-20261105_115628_822053_CBD994E2 X-CRM114-Status: GOOD ( 20.18 ) X-Spam-Score: -0.2 (/) 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 , Pratyush Yadav Sender: "kexec" X-Spam-Status: No, score=-12.3 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, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 11/5/26 8:59 AM, Mike Rapoport wrote: > On Wed, Nov 04, 2026 at 09:42:17PM +0100, Jose A. Perez de Azpillaga wrote: >> On a KHO boot, a reserve_mem region that can't be revived is allocated >> from KHO_NOPRSRV memory, which includes the bootmem the next kernel >> boots out of. With CONFIG_KEXEC_HANDOVER_DEBUG, preserving the region >> then fails: >> >> WARNING: kernel/liveupdate/kexec_handover.c:1245 at kho_preserve_pages+0x168/0x180 >> failed to prepare memblock FDT for KHO: -22 >> >> Without it, the next kernel puts its memmap on top of the region and >> the ramoops records in it are lost. >> >> There is no use case for adding regions across a live update, so fail >> instead of allocating, and drop the TODO. >> >> Fixes: f99230780211 ("memblock: add KHO support for reserve_mem") >> Signed-off-by: Jose A. Perez de Azpillaga >> --- >> Changes in v2: >> - fail on a KHO boot instead of allocating outside bootmem, as agreed >> with Pratyush [1]. this drops v1's patch 1. >> - not an RFC anymore. >> - based on v7.4-rc1. >> >> v1: https://lore.kernel.org/all/20261021211058.83483-3-azpijr@gmail.com/ >> >> [1] https://lore.kernel.org/all/2vxzfqxglrg6.fsf@kernel.org/ >> >> mm/memblock.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/mm/memblock.c b/mm/memblock.c >> index a450092a80fb..e325e0542c9a 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -2827,7 +2827,16 @@ static int __init reserve_mem(char *p) >> if (reserve_mem_kho_revive(name, size, align)) >> return 1; >> >> - /* TODO: Allocation must be outside of KHO_NOPRSRV region */ >> + /* >> + * On a KHO boot memblock only allocates from KHO_NOPRSRV memory here, >> + * which includes the bootmem the next kernel boots out of. Only regions >> + * handed over by the previous kernel are supported. >> + */ >> + if (is_kho_boot()) { > > This breaks memblock tests, please add a stub there. oops, sorry. will add it in v3 :) -- cheers, jose a. p-a From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 71A48606A32C for ; Thu, 5 Nov 2026 11:56:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256 header.s=20260707 header.b=Ag5J149Z Received: by kanga.kvack.org (Postfix) id 999D56B05B2; Thu, 5 Nov 2026 06:56:33 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 949F56B05B3; Thu, 5 Nov 2026 06:56:33 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 860986B05B9; Thu, 5 Nov 2026 06:56:33 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 61A2C6B05B2 for ; 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Thu, 05 Nov 2026 03:56:26 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fea181085sm9708651f8f.1.2026.11.05.03.56.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Nov 2026 03:56:26 -0800 (PST) Message-ID: Date: Thu, 5 Nov 2026 12:56:24 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] memblock: don't allocate new reserve_mem regions on a KHO boot To: Mike Rapoport Cc: Andrew Morton , Kees Cook , Changyuan Lyu , Alexander Graf , Tony Luck , "Guilherme G. Piccoli" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Pratyush Yadav , Pasha Tatashin , kexec@lists.infradead.org References: <20261104204235.9066-1-azpijr@gmail.com> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Stat-Signature: 5kksdt396fy9sszfbi6p4zwwfzguhpxc X-Spam-Status: No, score=-14.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: 858CA10000C X-Rspam-User: X-HE-Tag: 1793879788-289574 X-HE-Meta: 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 IL0ZLFt+ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 11/5/26 8:59 AM, Mike Rapoport wrote: > On Wed, Nov 04, 2026 at 09:42:17PM +0100, Jose A. Perez de Azpillaga wrote: >> On a KHO boot, a reserve_mem region that can't be revived is allocated >> from KHO_NOPRSRV memory, which includes the bootmem the next kernel >> boots out of. With CONFIG_KEXEC_HANDOVER_DEBUG, preserving the region >> then fails: >> >> WARNING: kernel/liveupdate/kexec_handover.c:1245 at kho_preserve_pages+0x168/0x180 >> failed to prepare memblock FDT for KHO: -22 >> >> Without it, the next kernel puts its memmap on top of the region and >> the ramoops records in it are lost. >> >> There is no use case for adding regions across a live update, so fail >> instead of allocating, and drop the TODO. >> >> Fixes: f99230780211 ("memblock: add KHO support for reserve_mem") >> Signed-off-by: Jose A. Perez de Azpillaga >> --- >> Changes in v2: >> - fail on a KHO boot instead of allocating outside bootmem, as agreed >> with Pratyush [1]. this drops v1's patch 1. >> - not an RFC anymore. >> - based on v7.4-rc1. >> >> v1: https://lore.kernel.org/all/20261021211058.83483-3-azpijr@gmail.com/ >> >> [1] https://lore.kernel.org/all/2vxzfqxglrg6.fsf@kernel.org/ >> >> mm/memblock.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/mm/memblock.c b/mm/memblock.c >> index a450092a80fb..e325e0542c9a 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -2827,7 +2827,16 @@ static int __init reserve_mem(char *p) >> if (reserve_mem_kho_revive(name, size, align)) >> return 1; >> >> - /* TODO: Allocation must be outside of KHO_NOPRSRV region */ >> + /* >> + * On a KHO boot memblock only allocates from KHO_NOPRSRV memory here, >> + * which includes the bootmem the next kernel boots out of. Only regions >> + * handed over by the previous kernel are supported. >> + */ >> + if (is_kho_boot()) { > > This breaks memblock tests, please add a stub there. oops, sorry. will add it in v3 :) -- cheers, jose a. p-a