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Perez de Azpillaga" 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 Subject: Re: [PATCH v2] memblock: don't allocate new reserve_mem regions on a KHO boot Message-ID: References: <20261104204235.9066-1-azpijr@gmail.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261104204235.9066-1-azpijr@gmail.com> X-Stat-Signature: ju7y5rrtwcxde63ifayaszagqbjsyk3b X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2AFE740003 X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=unavailable autolearn_force=no version=4.0.1 X-HE-Tag: 1793865599-7434 X-HE-Meta: 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 +Mzzxbez RxsL2NKXswWbfmA1sVH16KSSlq2fbgw/ZRIVbIhk8QQ1zjtI6MPRxv+Un1y58/OcfNQO0NiL3Vd2H2HuTC6tl/y+DJoOO85kkQ/JMhjtyWzSJJEzgN8QRWr8Fp0K801O5bdvyqUyJwniRugUJ+q4eWtpgW2ACfaA62Q9yNCWrQOKtQ5anZZuA3k6SLXQVz3VRZN8n72HuVGAI3gNttDELLFSp+e/fJju5FvYwiyBYj6vgVbnfqMRzVlTzIsXq8YPSEeMzguQLFtRbWL81wK6EXog8VSRrxoJ517yAojFlJOkyEi7eNoEQja7pXCIeJfmM9CQ3Zkn9QFQCVrbDrywqLUMDtNKqR22zUbpb 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 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. > + pr_err("reserve_mem: can't allocate \"%s\" on a KHO boot\n", name); > + return -EOPNOTSUPP; > + } > + > start = memblock_phys_alloc(size, align); > if (!start) { > pr_err("reserve_mem: memblock allocation failed\n"); > > base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4 > -- > 2.56.0 > -- Sincerely yours, Mike.