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[34.85.221.182]) by smtp.gmail.com with ESMTPSA id 00721157ae682-78822125317sm16468577b3.37.2025.11.14.07.54.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 14 Nov 2025 07:54:11 -0800 (PST) From: Pasha Tatashin To: akpm@linux-foundation.org, bhe@redhat.com, pasha.tatashin@soleen.com, rppt@kernel.org, jasonmiu@google.com, arnd@arndb.de, coxu@redhat.com, dave@vasilevsky.ca, ebiggers@google.com, graf@amazon.com, kees@kernel.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: [PATCH v1 09/13] kho: Update FDT dynamically for subtree addition/removal Date: Fri, 14 Nov 2025 10:53:54 -0500 Message-ID: <20251114155358.2884014-10-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.52.0.rc1.455.g30608eb744-goog In-Reply-To: <20251114155358.2884014-1-pasha.tatashin@soleen.com> References: <20251114155358.2884014-1-pasha.tatashin@soleen.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, sub-FDTs were tracked in a list (kho_out.sub_fdts) and the final FDT is constructed entirely from scratch during kho_finalize(). We can maintain the FDT dynamically: 1. Initialize a valid, empty FDT in kho_init(). 2. Use fdt_add_subnode and fdt_setprop in kho_add_subtree to update the FDT immediately when a subsystem registers. 3. Use fdt_del_node in kho_remove_subtree to remove entries. This removes the need for the intermediate sub_fdts list and the reconstruction logic in kho_finalize(). kho_finalize() now only needs to trigger memory map serialization. Signed-off-by: Pasha Tatashin Reviewed-by: Pratyush Yadav --- kernel/liveupdate/kexec_handover.c | 144 ++++++++++++++--------------- 1 file changed, 68 insertions(+), 76 deletions(-) diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_h= andover.c index 8ab77cb85ca9..822da961d4c9 100644 --- a/kernel/liveupdate/kexec_handover.c +++ b/kernel/liveupdate/kexec_handover.c @@ -102,20 +102,11 @@ struct kho_mem_track { =20 struct khoser_mem_chunk; =20 -struct kho_sub_fdt { - struct list_head l; - const char *name; - void *fdt; -}; - struct kho_out { void *fdt; bool finalized; struct mutex lock; /* protects KHO FDT finalization */ =20 - struct list_head sub_fdts; - struct mutex fdts_lock; - struct kho_mem_track track; struct kho_debugfs dbg; }; @@ -125,8 +116,6 @@ static struct kho_out kho_out =3D { .track =3D { .orders =3D XARRAY_INIT(kho_out.track.orders, 0), }, - .sub_fdts =3D LIST_HEAD_INIT(kho_out.sub_fdts), - .fdts_lock =3D __MUTEX_INITIALIZER(kho_out.fdts_lock), .finalized =3D false, }; =20 @@ -724,37 +713,67 @@ static void __init kho_reserve_scratch(void) */ int kho_add_subtree(const char *name, void *fdt) { - struct kho_sub_fdt *sub_fdt; + phys_addr_t phys =3D virt_to_phys(fdt); + void *root_fdt =3D kho_out.fdt; + int err =3D -ENOMEM; + int off, fdt_err; =20 - sub_fdt =3D kmalloc(sizeof(*sub_fdt), GFP_KERNEL); - if (!sub_fdt) - return -ENOMEM; + guard(mutex)(&kho_out.lock); + + fdt_err =3D fdt_open_into(root_fdt, root_fdt, PAGE_SIZE); + if (fdt_err < 0) + return err; =20 - INIT_LIST_HEAD(&sub_fdt->l); - sub_fdt->name =3D name; - sub_fdt->fdt =3D fdt; + off =3D fdt_add_subnode(root_fdt, 0, name); + if (off < 0) { + if (off =3D=3D -FDT_ERR_EXISTS) + err =3D -EEXIST; + goto out_pack; + } + + err =3D fdt_setprop(root_fdt, off, PROP_SUB_FDT, &phys, sizeof(phys)); + if (err < 0) + goto out_pack; =20 - guard(mutex)(&kho_out.fdts_lock); - list_add_tail(&sub_fdt->l, &kho_out.sub_fdts); WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, name, fdt, false)); =20 - return 0; +out_pack: + fdt_pack(root_fdt); + + return err; } EXPORT_SYMBOL_GPL(kho_add_subtree); =20 void kho_remove_subtree(void *fdt) { - struct kho_sub_fdt *sub_fdt; + phys_addr_t target_phys =3D virt_to_phys(fdt); + void *root_fdt =3D kho_out.fdt; + int off; + int err; + + guard(mutex)(&kho_out.lock); =20 - guard(mutex)(&kho_out.fdts_lock); - list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) { - if (sub_fdt->fdt =3D=3D fdt) { - list_del(&sub_fdt->l); - kfree(sub_fdt); + err =3D fdt_open_into(root_fdt, root_fdt, PAGE_SIZE); + if (err < 0) + return; + + for (off =3D fdt_first_subnode(root_fdt, 0); off >=3D 0; + off =3D fdt_next_subnode(root_fdt, off)) { + const u64 *val; + int len; + + val =3D fdt_getprop(root_fdt, off, PROP_SUB_FDT, &len); + if (!val || len !=3D sizeof(phys_addr_t)) + continue; + + if ((phys_addr_t)*val =3D=3D target_phys) { + fdt_del_node(root_fdt, off); kho_debugfs_fdt_remove(&kho_out.dbg, fdt); break; } } + + fdt_pack(root_fdt); } EXPORT_SYMBOL_GPL(kho_remove_subtree); =20 @@ -1145,48 +1164,6 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *= preservation) } EXPORT_SYMBOL_GPL(kho_restore_vmalloc); =20 -static int __kho_finalize(void) -{ - void *root =3D kho_out.fdt; - struct kho_sub_fdt *fdt; - u64 empty_mem_map =3D 0; - int err; - - err =3D fdt_create(root, PAGE_SIZE); - err |=3D fdt_finish_reservemap(root); - err |=3D fdt_begin_node(root, ""); - err |=3D fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE); - err |=3D fdt_property(root, PROP_PRESERVED_MEMORY_MAP, &empty_mem_map, - sizeof(empty_mem_map)); - if (err) - goto err_exit; - - mutex_lock(&kho_out.fdts_lock); - list_for_each_entry(fdt, &kho_out.sub_fdts, l) { - phys_addr_t phys =3D virt_to_phys(fdt->fdt); - - err |=3D fdt_begin_node(root, fdt->name); - err |=3D fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys)); - err |=3D fdt_end_node(root); - } - mutex_unlock(&kho_out.fdts_lock); - - err |=3D fdt_end_node(root); - err |=3D fdt_finish(root); - if (err) - goto err_exit; - - err =3D kho_mem_serialize(&kho_out); - if (err) - goto err_exit; - - return 0; - -err_exit: - pr_err("Failed to convert KHO state tree: %d\n", err); - return err; -} - int kho_finalize(void) { int ret; @@ -1195,12 +1172,7 @@ int kho_finalize(void) return -EOPNOTSUPP; =20 guard(mutex)(&kho_out.lock); - if (kho_out.finalized) { - kho_update_memory_map(NULL); - kho_out.finalized =3D false; - } - - ret =3D __kho_finalize(); + ret =3D kho_mem_serialize(&kho_out); if (ret) return ret; =20 @@ -1285,6 +1257,26 @@ int kho_retrieve_subtree(const char *name, phys_addr= _t *phys) } EXPORT_SYMBOL_GPL(kho_retrieve_subtree); =20 +static __init int kho_out_fdt_setup(void) +{ + void *root =3D kho_out.fdt; + u64 empty_mem_map =3D 0; + int err; + + err =3D fdt_create(root, PAGE_SIZE); + err |=3D fdt_finish_reservemap(root); + err |=3D fdt_begin_node(root, ""); + err |=3D fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE); + err |=3D fdt_property(root, PROP_PRESERVED_MEMORY_MAP, &empty_mem_map, + sizeof(empty_mem_map)); + err |=3D fdt_end_node(root); + err |=3D fdt_finish(root); + if (err) + return err; + + return kho_preserve_folio(virt_to_folio(kho_out.fdt)); +} + static __init int kho_init(void) { int err =3D 0; @@ -1309,7 +1301,7 @@ static __init int kho_init(void) if (err) goto err_free_fdt; =20 - err =3D kho_preserve_folio(virt_to_folio(kho_out.fdt)); + err =3D kho_out_fdt_setup(); if (err) goto err_free_fdt; =20 --=20 2.52.0.rc1.455.g30608eb744-goog