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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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: D93314000E X-Stat-Signature: gmtrmobj1mmmn8cjx3ram1n9tay8c3zi X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1763135652-241624 X-HE-Meta: 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 zdBMQjvt +nacvPgporhZ05EnJcaGgLZz8HYeH+6WjKrIwo0i9/glVR6bjKXdF1xFQ41Z1YgKfy8ox9Ot1Dpz591ipabzedLcLLINHIO0qX/sNGCz0A5pItM38Fvd/I/S+c50FF5ZSApo5sC2JpRy5qvG9Mb18COC71ez7Vnqln8JtI+pBtEtB04I+Ru1ymKUvhABLlu1XHrEd295ORbcFGh/CpRRzBGYO5TlzEJJKlgLdKdkUICumy/Al+mJ4MGZl5CVT3tWW+LVMtEygY8kM+k3w8l3uur7+UQTPLlGtRiOqDSY7gs5omvIjGDK7cAvWcq90dSRYfDYN5eMGiz5fnF8= 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: 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 --- 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_handover.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 { struct khoser_mem_chunk; -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 */ - 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 = { .track = { .orders = XARRAY_INIT(kho_out.track.orders, 0), }, - .sub_fdts = LIST_HEAD_INIT(kho_out.sub_fdts), - .fdts_lock = __MUTEX_INITIALIZER(kho_out.fdts_lock), .finalized = false, }; @@ -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 = virt_to_phys(fdt); + void *root_fdt = kho_out.fdt; + int err = -ENOMEM; + int off, fdt_err; - sub_fdt = kmalloc(sizeof(*sub_fdt), GFP_KERNEL); - if (!sub_fdt) - return -ENOMEM; + guard(mutex)(&kho_out.lock); + + fdt_err = fdt_open_into(root_fdt, root_fdt, PAGE_SIZE); + if (fdt_err < 0) + return err; - INIT_LIST_HEAD(&sub_fdt->l); - sub_fdt->name = name; - sub_fdt->fdt = fdt; + off = fdt_add_subnode(root_fdt, 0, name); + if (off < 0) { + if (off == -FDT_ERR_EXISTS) + err = -EEXIST; + goto out_pack; + } + + err = fdt_setprop(root_fdt, off, PROP_SUB_FDT, &phys, sizeof(phys)); + if (err < 0) + goto out_pack; - 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)); - return 0; +out_pack: + fdt_pack(root_fdt); + + return err; } EXPORT_SYMBOL_GPL(kho_add_subtree); void kho_remove_subtree(void *fdt) { - struct kho_sub_fdt *sub_fdt; + phys_addr_t target_phys = virt_to_phys(fdt); + void *root_fdt = kho_out.fdt; + int off; + int err; + + guard(mutex)(&kho_out.lock); - guard(mutex)(&kho_out.fdts_lock); - list_for_each_entry(sub_fdt, &kho_out.sub_fdts, l) { - if (sub_fdt->fdt == fdt) { - list_del(&sub_fdt->l); - kfree(sub_fdt); + err = fdt_open_into(root_fdt, root_fdt, PAGE_SIZE); + if (err < 0) + return; + + for (off = fdt_first_subnode(root_fdt, 0); off >= 0; + off = fdt_next_subnode(root_fdt, off)) { + const u64 *val; + int len; + + val = fdt_getprop(root_fdt, off, PROP_SUB_FDT, &len); + if (!val || len != sizeof(phys_addr_t)) + continue; + + if ((phys_addr_t)*val == 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); @@ -1145,48 +1164,6 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation) } EXPORT_SYMBOL_GPL(kho_restore_vmalloc); -static int __kho_finalize(void) -{ - void *root = kho_out.fdt; - struct kho_sub_fdt *fdt; - u64 empty_mem_map = 0; - int err; - - err = fdt_create(root, PAGE_SIZE); - err |= fdt_finish_reservemap(root); - err |= fdt_begin_node(root, ""); - err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE); - err |= 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 = virt_to_phys(fdt->fdt); - - err |= fdt_begin_node(root, fdt->name); - err |= fdt_property(root, PROP_SUB_FDT, &phys, sizeof(phys)); - err |= fdt_end_node(root); - } - mutex_unlock(&kho_out.fdts_lock); - - err |= fdt_end_node(root); - err |= fdt_finish(root); - if (err) - goto err_exit; - - err = 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; guard(mutex)(&kho_out.lock); - if (kho_out.finalized) { - kho_update_memory_map(NULL); - kho_out.finalized = false; - } - - ret = __kho_finalize(); + ret = kho_mem_serialize(&kho_out); if (ret) return ret; @@ -1285,6 +1257,26 @@ int kho_retrieve_subtree(const char *name, phys_addr_t *phys) } EXPORT_SYMBOL_GPL(kho_retrieve_subtree); +static __init int kho_out_fdt_setup(void) +{ + void *root = kho_out.fdt; + u64 empty_mem_map = 0; + int err; + + err = fdt_create(root, PAGE_SIZE); + err |= fdt_finish_reservemap(root); + err |= fdt_begin_node(root, ""); + err |= fdt_property_string(root, "compatible", KHO_FDT_COMPATIBLE); + err |= fdt_property(root, PROP_PRESERVED_MEMORY_MAP, &empty_mem_map, + sizeof(empty_mem_map)); + err |= fdt_end_node(root); + err |= 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 = 0; @@ -1309,7 +1301,7 @@ static __init int kho_init(void) if (err) goto err_free_fdt; - err = kho_preserve_folio(virt_to_folio(kho_out.fdt)); + err = kho_out_fdt_setup(); if (err) goto err_free_fdt; -- 2.52.0.rc1.455.g30608eb744-goog