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h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ED82mNNRqJ3jL9ehZj1qNyPphPq68PfaTZpFEelfjITAU4qGtuUKf/8h/2qFQbOTb z1KR9ENADYHkDYhyQE6kcTPvpTGMdCXLpadop2cSDHl4+GXDg4PBoicMiNEMm93lql VoiWY85vHidBbxkYTZ70BhkP/e8UPe+czQAAmn+DX+aBVknZC79AHLEzoG9ha0j+am SCP54gQMgxT+XKxQYhkvv9+OywRKrIOC1wzvIFNuysd/RhrPoFyZJm2dOHpUU+R+w8 WeoTskL6dViCKt7nP6rDJodk39ucVwwiAZWczO/dN0uXB6SZ4GcR2uXwwiAVO5IZ5L DXoHwdlQ8sxxg== Date: Sun, 26 Oct 2025 18:23:35 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: akpm@linux-foundation.org, brauner@kernel.org, corbet@lwn.net, graf@amazon.com, jgg@ziepe.ca, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, masahiroy@kernel.org, ojeda@kernel.org, pratyush@kernel.org, rdunlap@infradead.org, tj@kernel.org Subject: Re: [PATCH v8 3/8] kho: drop notifiers Message-ID: References: <20251024161002.747372-1-pasha.tatashin@soleen.com> <20251024161002.747372-4-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251024161002.747372-4-pasha.tatashin@soleen.com> X-Rspam-User: X-Stat-Signature: thw67fgy6c63x9hjrbgq99k1edmry7xc X-Rspamd-Queue-Id: 236BD40009 X-Rspamd-Server: rspam09 X-HE-Tag: 1761495824-74003 X-HE-Meta: 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 DLfmiOi5 C7yvtKnKrsBHyY2hbcmryN9E3NPtNcwJloEL0PEOciGc+hnIjFZsqNXRtdZ9LN75cRpdH+csbu//BK24sc4bZjB4lgJocqDaPe9LvtY4YAlN1lahAOQHUg+6lFk5WjRBrDDflUPtIUWPH9mNL3Rf3Cdyn9Y3t7PaaI9Ta3XSWNqYg+FTJ/exrM0ExUzN10DrUY+jiNRPUFdrJKte4zEm8gxZE/Om3kiROREQMfKwKiW7vPLJ9ln+YuN8055o6fOioMMEssVwRKpWOizd+mNBfgtuzcDi/oGTUdmEC2JkwXIYehnM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Oct 24, 2025 at 12:09:57PM -0400, Pasha Tatashin wrote: > From: "Mike Rapoport (Microsoft)" > > The KHO framework uses a notifier chain as the mechanism for clients to > participate in the finalization process. While this works for a single, > central state machine, it is too restrictive for kernel-internal > components like pstore/reserve_mem or IMA. These components need a > simpler, direct way to register their state for preservation (e.g., > during their initcall) without being part of a complex, > shutdown-time notifier sequence. The notifier model forces all > participants into a single finalization flow and makes direct > preservation from an arbitrary context difficult. > This patch refactors the client participation model by removing the > notifier chain and introducing a direct API for managing FDT subtrees. > > The core kho_finalize() and kho_abort() state machine remains, but > clients now register their data with KHO beforehand. > > Signed-off-by: Mike Rapoport (Microsoft) > Co-developed-by: Pasha Tatashin > Signed-off-by: Pasha Tatashin > --- > include/linux/kexec_handover.h | 28 +----- > kernel/kexec_handover.c | 166 +++++++++++++++++-------------- > kernel/kexec_handover_debugfs.c | 17 ++-- > kernel/kexec_handover_internal.h | 5 +- > lib/test_kho.c | 33 +----- > mm/memblock.c | 62 +++--------- > 6 files changed, 126 insertions(+), 185 deletions(-) > diff --git a/lib/test_kho.c b/lib/test_kho.c > index 60cd899ea745..1c6c4ce83666 100644 > --- a/lib/test_kho.c > +++ b/lib/test_kho.c > @@ -120,6 +93,7 @@ static int kho_test_prepare_fdt(struct kho_test_state *state) > > fdt = folio_address(state->fdt); > > + err |= kho_preserve_folio(state->fdt); We should bail out here, no point creating an fdt if it won't be preserved. > err |= fdt_create(fdt, fdt_size); > err |= fdt_finish_reservemap(fdt); > > @@ -131,6 +105,7 @@ static int kho_test_prepare_fdt(struct kho_test_state *state) > > err |= fdt_finish(fdt); > > + err = kho_add_subtree(KHO_TEST_FDT, folio_address(state->fdt)); > if (err) > folio_put(state->fdt); > > @@ -203,7 +178,7 @@ static int kho_test_save(void) > if (err) > goto err_free_folios; > > - err = register_kho_notifier(&kho_test_nb); > + err = kho_add_subtree(KHO_TEST_FDT, folio_address(state->fdt)); This is the second time we add the same subtree, isn't it? > if (err) > goto err_free_fdt; > > @@ -326,7 +301,7 @@ static void kho_test_cleanup(void) > > static void __exit kho_test_exit(void) > { > - unregister_kho_notifier(&kho_test_nb); > + kho_remove_subtree(folio_address(kho_test_state.fdt)); > kho_test_cleanup(); > } > module_exit(kho_test_exit); > diff --git a/mm/memblock.c b/mm/memblock.c > index e23e16618e9b..e3bef9b35d63 100644 > --- a/mm/memblock.c > +++ b/mm/memblock.c > static int __init prepare_kho_fdt(void) > { > int err = 0, i; > + struct page *fdt_page; > void *fdt; > > - kho_fdt = alloc_page(GFP_KERNEL); > - if (!kho_fdt) > + fdt_page = alloc_page(GFP_KERNEL); > + if (!fdt_page) > return -ENOMEM; > > - fdt = page_to_virt(kho_fdt); > + fdt = page_to_virt(fdt_page); > > err |= fdt_create(fdt, PAGE_SIZE); > err |= fdt_finish_reservemap(fdt); > @@ -2499,7 +2464,10 @@ static int __init prepare_kho_fdt(void) > err |= fdt_property_string(fdt, "compatible", MEMBLOCK_KHO_NODE_COMPATIBLE); > for (i = 0; i < reserved_mem_count; i++) { > struct reserve_mem_table *map = &reserved_mem_table[i]; > + struct page *page = phys_to_page(map->start); > + unsigned int nr_pages = map->size >> PAGE_SHIFT; > > + err |= kho_preserve_pages(page, nr_pages); > err |= fdt_begin_node(fdt, map->name); > err |= fdt_property_string(fdt, "compatible", RESERVE_MEM_KHO_NODE_COMPATIBLE); > err |= fdt_property(fdt, "start", &map->start, sizeof(map->start)); > @@ -2507,13 +2475,16 @@ static int __init prepare_kho_fdt(void) > err |= fdt_end_node(fdt); > } > err |= fdt_end_node(fdt); > - > err |= fdt_finish(fdt); > > + err |= kho_preserve_folio(page_folio(fdt_page)); When looking at the end result after patch 8 it becomes a total mess. Let's move this right after the allocation and make it err = kho_preserve_folio(page_folio(fdt_page); if (err) goto err_free_fdt; > + > + if (!err) > + err = kho_add_subtree(MEMBLOCK_KHO_FDT, fdt); and replace this pattern with usual kernel if (err) goto err_free_fdt; err = kho_add_subtree(MEMBLOCK_KHO_FDT, fdt); if (err) goto err_free_fdt; so that only fdt operations will be a part of err |= fdt_ sequence. > if (err) { > pr_err("failed to prepare memblock FDT for KHO: %d\n", err); > - put_page(kho_fdt); > - kho_fdt = NULL; > + put_page(fdt_page); > } > > return err; > @@ -2529,13 +2500,6 @@ static int __init reserve_mem_init(void) > err = prepare_kho_fdt(); > if (err) > return err; > - > - err = register_kho_notifier(&reserve_mem_kho_nb); > - if (err) { > - put_page(kho_fdt); > - kho_fdt = NULL; > - } > - > return err; > } > late_initcall(reserve_mem_init); > -- > 2.51.1.821.gb6fe4d2222-goog > > -- Sincerely yours, Mike.