+ kho-print-which-scratch-buffer-failed-to-be-reserved.patch added to mm-nonmm-unstable branch

+ kho-print-which-scratch-buffer-failed-to-be-reserved.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: kho: print which scratch buffer failed to be reserved
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     kho-print-which-scratch-buffer-failed-to-be-reserved.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kho-print-which-scratch-buffer-failed-to-be-reserved.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Pratyush Yadav (Google)" <pratyush@kernel.org>
Subject: kho: print which scratch buffer failed to be reserved
Date: Fri, 16 Jan 2026 16:54:11 +0000

When scratch area fails to reserve, KHO prints a message indicating that. 
But it doesn't say which scratch failed to allocate.  This can be useful
information for debugging.  Even more so when the failure is hard to
reproduce.

Along with the current message, also print which exact scratch area failed
to be reserved.

Link: https://lkml.kernel.org/r/20260116165416.1262531-1-pratyush@kernel.org
Signed-off-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/liveupdate/kexec_handover.c |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

--- a/kernel/liveupdate/kexec_handover.c~kho-print-which-scratch-buffer-failed-to-be-reserved
+++ a/kernel/liveupdate/kexec_handover.c
@@ -651,8 +651,10 @@ static void __init kho_reserve_scratch(v
 	kho_scratch_cnt = num_online_nodes() + 2;
 	size = kho_scratch_cnt * sizeof(*kho_scratch);
 	kho_scratch = memblock_alloc(size, PAGE_SIZE);
-	if (!kho_scratch)
+	if (!kho_scratch) {
+		pr_err("Failed to reserve scratch array\n");
 		goto err_disable_kho;
+	}
 
 	/*
 	 * reserve scratch area in low memory for lowmem allocations in the
@@ -661,8 +663,10 @@ static void __init kho_reserve_scratch(v
 	size = scratch_size_lowmem;
 	addr = memblock_phys_alloc_range(size, CMA_MIN_ALIGNMENT_BYTES, 0,
 					 ARCH_LOW_ADDRESS_LIMIT);
-	if (!addr)
+	if (!addr) {
+		pr_err("Failed to reserve lowmem scratch buffer\n");
 		goto err_free_scratch_desc;
+	}
 
 	kho_scratch[i].addr = addr;
 	kho_scratch[i].size = size;
@@ -671,8 +675,10 @@ static void __init kho_reserve_scratch(v
 	/* reserve large contiguous area for allocations without nid */
 	size = scratch_size_global;
 	addr = memblock_phys_alloc(size, CMA_MIN_ALIGNMENT_BYTES);
-	if (!addr)
+	if (!addr) {
+		pr_err("Failed to reserve global scratch buffer\n");
 		goto err_free_scratch_areas;
+	}
 
 	kho_scratch[i].addr = addr;
 	kho_scratch[i].size = size;
@@ -683,8 +689,10 @@ static void __init kho_reserve_scratch(v
 		addr = memblock_alloc_range_nid(size, CMA_MIN_ALIGNMENT_BYTES,
 						0, MEMBLOCK_ALLOC_ACCESSIBLE,
 						nid, true);
-		if (!addr)
+		if (!addr) {
+			pr_err("Failed to reserve nid %d scratch buffer\n", nid);
 			goto err_free_scratch_areas;
+		}
 
 		kho_scratch[i].addr = addr;
 		kho_scratch[i].size = size;
_

Patches currently in -mm which might be from pratyush@kernel.org are

kho-simplify-page-initialization-in-kho_restore_page.patch
kho-print-which-scratch-buffer-failed-to-be-reserved.patch