linux-kernel - [PATCH v1 08/13] kho: Remove abort functionality and support state refresh

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Message-ID: <20251114155358.2884014-9-pasha.tatashin@soleen.com>
Date: Fri, 14 Nov 2025 10:53:53 -0500
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: akpm@...ux-foundation.org,
	bhe@...hat.com,
	pasha.tatashin@...een.com,
	rppt@...nel.org,
	jasonmiu@...gle.com,
	arnd@...db.de,
	coxu@...hat.com,
	dave@...ilevsky.ca,
	ebiggers@...gle.com,
	graf@...zon.com,
	kees@...nel.org,
	linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org,
	linux-mm@...ck.org
Subject: [PATCH v1 08/13] kho: Remove abort functionality and support state refresh

Previously, KHO required a dedicated kho_abort() function to clean up
state before kho_finalize() could be called again. This was necessary
to handle complex unwind paths when using notifiers.

With the shift to direct memory preservation, the explicit abort step
is no longer strictly necessary.

Remove kho_abort() and refactor kho_finalize() to handle re-entry.
If kho_finalize() is called while KHO is already finalized, it will
now automatically clean up the previous memory map and state before
generating a new one. This allows the KHO state to be updated/refreshed
simply by triggering finalize again.

Update debugfs to return -EINVAL if userspace attempts to write 0 to
the finalize attribute, as explicit abort is no longer supported.

Suggested-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
---
 kernel/liveupdate/kexec_handover.c          | 21 ++++-----------------
 kernel/liveupdate/kexec_handover_debugfs.c  |  2 +-
 kernel/liveupdate/kexec_handover_internal.h |  1 -
 3 files changed, 5 insertions(+), 19 deletions(-)

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index f1c3dd1ef680..8ab77cb85ca9 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -1145,21 +1145,6 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
 }
 EXPORT_SYMBOL_GPL(kho_restore_vmalloc);
 
-int kho_abort(void)
-{
-	if (!kho_enable)
-		return -EOPNOTSUPP;
-
-	guard(mutex)(&kho_out.lock);
-	if (!kho_out.finalized)
-		return -ENOENT;
-
-	kho_update_memory_map(NULL);
-	kho_out.finalized = false;
-
-	return 0;
-}
-
 static int __kho_finalize(void)
 {
 	void *root = kho_out.fdt;
@@ -1210,8 +1195,10 @@ int kho_finalize(void)
 		return -EOPNOTSUPP;
 
 	guard(mutex)(&kho_out.lock);
-	if (kho_out.finalized)
-		return -EEXIST;
+	if (kho_out.finalized) {
+		kho_update_memory_map(NULL);
+		kho_out.finalized = false;
+	}
 
 	ret = __kho_finalize();
 	if (ret)
diff --git a/kernel/liveupdate/kexec_handover_debugfs.c b/kernel/liveupdate/kexec_handover_debugfs.c
index ac739d25094d..2abbf62ba942 100644
--- a/kernel/liveupdate/kexec_handover_debugfs.c
+++ b/kernel/liveupdate/kexec_handover_debugfs.c
@@ -87,7 +87,7 @@ static int kho_out_finalize_set(void *data, u64 val)
 	if (val)
 		return kho_finalize();
 	else
-		return kho_abort();
+		return -EINVAL;
 }
 
 DEFINE_DEBUGFS_ATTRIBUTE(kho_out_finalize_fops, kho_out_finalize_get,
diff --git a/kernel/liveupdate/kexec_handover_internal.h b/kernel/liveupdate/kexec_handover_internal.h
index 52ed73659fe6..0202c85ad14f 100644
--- a/kernel/liveupdate/kexec_handover_internal.h
+++ b/kernel/liveupdate/kexec_handover_internal.h
@@ -24,7 +24,6 @@ extern unsigned int kho_scratch_cnt;
 
 bool kho_finalized(void);
 int kho_finalize(void);
-int kho_abort(void);
 
 #ifdef CONFIG_KEXEC_HANDOVER_DEBUGFS
 int kho_debugfs_init(void);
-- 
2.52.0.rc1.455.g30608eb744-goog