linux-kernel - [PATCH] kho: print which scratch buffer failed to be reserved

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Message-ID: <20260116165416.1262531-1-pratyush@kernel.org>
Date: Fri, 16 Jan 2026 16:54:11 +0000
From: Pratyush Yadav <pratyush@...nel.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Graf <graf@...zon.com>,
	Mike Rapoport <rppt@...nel.org>,
	Pasha Tatashin <pasha.tatashin@...een.com>,
	Pratyush Yadav <pratyush@...nel.org>
Cc: kexec@...ts.infradead.org,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Samiullah Khawaja <skhawaja@...gle.com>,
	David Matlack <dmatlack@...gle.com>,
	Jason Miu <jasonmiu@...gle.com>
Subject: [PATCH] kho: print which scratch buffer failed to be reserved

From: "Pratyush Yadav (Google)" <pratyush@...nel.org>

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.

Signed-off-by: Pratyush Yadav (Google) <pratyush@...nel.org>
---
 kernel/liveupdate/kexec_handover.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index 49bf2cecab12..636bd96780ae 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -651,8 +651,10 @@ static void __init kho_reserve_scratch(void)
 	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(void)
 	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(void)
 	/* 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(void)
 		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;

base-commit: c37fac0551448c68e36f14782acaf662c7a1775e
-- 
2.52.0.457.g6b5491de43-goog