From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B6ABE21A449 for ; Sun, 18 May 2025 14:23:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747578206; cv=none; b=GVPJdRqeGO1Ne/NeA0EGFJsdr2u2VoR/DlckDzkxP9pDAZTQkLVngLZ79rtHBkGIBdDRbiP/PC8zU0Ctt6ZI6KQVy8JZcj7HYcX8uoZoaHrqovyASAl5LNE7xXNurXMr7bOlGP664KlsmQKWjbr8ylcDWoyf/K4MfrvTAsi0ztI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747578206; c=relaxed/simple; bh=HlY1Rgy1m/NrGt8ssBWeV2Cp9h8sHt3xlMmuqGbg52U=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Y7tn4g8V5TGuMmH3i1iTOsEhFpyV6LkhU2z5M+uw93YZUPQjs1DU+MREggxtwcIO/JaJ/gPaXKCt9XiTGxbntuGBwVct9IzEQQUj21aUfDr/m3nhZVPJk/9/s+dGetROgWXEDnau4972rONmXjtzOwBpNgNwfG4AIohNYF723pA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--changyuanl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=pEA4C0Xk; arc=none smtp.client-ip=209.85.214.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--changyuanl.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="pEA4C0Xk" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-231d4e36288so20956505ad.2 for ; Sun, 18 May 2025 07:23:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1747578204; x=1748183004; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=jT7mfe7LbtE5wHDmsO21gdSBNUHVNX5bvSxUgvXaBdw=; b=pEA4C0XkWsnnH/eeUcBT8OAL89n5zUMF6QnWIl7mivlMcrfAvmbEENizThcI/V1eGm sfcuLxpZ4cp6UkyJhKfMGPjWCT+hJ8vNOgvwuEGlmcD/gDxfaNpb/0rX9Vp0XKmVOPD1 HUa8cwGHBbLfvhDhrc8SKYUNiH+mVj02FFHfXobs9w1yg9mGEuewHHFXr0cJMC+rnKvH ETsL3d1SXl8MtU8VeKAF2pLiCf0Us0/samWgKXUVIRWVSVcZFUsf9zKCiJIhwPvsH1v/ b2thnZjsI2kEufaXUcaJWkVgMpLuJRkvzdLGNRXmbVL5NXr5sCOqufTtsg+C+QtJQP/7 Ta1g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747578204; x=1748183004; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=jT7mfe7LbtE5wHDmsO21gdSBNUHVNX5bvSxUgvXaBdw=; b=KLAnSVvpcmFE4EfqRTfIbna51lbg4if9PtCw/Tn1eQfzuKqJXF6xGc4+Lx6FySRBlV hFoNW2N7F8bE2HACq/fojkBeEEfE8fGGaOJMUj4Tf6AaShKf6ihD9mCPEktNeO8FnmRU BGg1RHwfGL4H5dcria92AYAeKYMZakqyNkEx9bLmflsJY2T1FRdYKV/7gEOeae7d1246 53WGvn5H8J88bi4tpm1vndUNPX9H9GubepAkJ3qf3mxBZRygAFMJA63wLUWB6hTKfgFq bJJBVE3pBtS9RLG4fx1uJHj84h0x3kvxmVqZy9DJE1oohcyxzJhmaA1MHKTeGftFGImm zAaw== X-Forwarded-Encrypted: i=1; AJvYcCWaKE40jTcHT38OJ4+Y3Mc1kKpkUi1kHldvi35uBFztf0wZVtpSRAH6ubIWETurUtM1CUbK1Kw7xRM5xBU=@vger.kernel.org X-Gm-Message-State: AOJu0Yx+FK1WzY44P22Ijsb7WtaXqNLQJ3wTCOx+Q8SqpY2A1n3SJUeU GAiYZ1ZVgPIcVlBfTp5bks7lnqBEXEfYtIWk5YON/EKF+3OZTG0TY+U8uVV6rgeuspejEZbbLAn 7S8aY4UWJAX7KvUKod083Kw== X-Google-Smtp-Source: AGHT+IGypgJXeP8ubYjhVjl0jk8L37IfHdOWll/4sSzsWQWyLqo/POjIy3VpEHrpZd9cWUYbykkM//Boenh7zHui X-Received: from ploh6.prod.google.com ([2002:a17:902:f706:b0:22e:3312:15a5]) (user=changyuanl job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:94f:b0:220:ea90:191e with SMTP id d9443c01a7336-231d43d9ca1mr147409035ad.4.1747578203986; Sun, 18 May 2025 07:23:23 -0700 (PDT) Date: Sun, 18 May 2025 07:23:14 -0700 In-Reply-To: <20250518142315.241670-1-changyuanl@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250518142315.241670-1-changyuanl@google.com> X-Mailer: git-send-email 2.49.0.1101.gccaa498523-goog Message-ID: <20250518142315.241670-2-changyuanl@google.com> Subject: [PATCH 1/2] memblock: show a warning if allocation in KHO scratch fails From: Changyuan Lyu To: rppt@kernel.org, akpm@linux-foundation.org Cc: graf@amazon.com, bhe@redhat.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, chrisl@kernel.org, pasha.tatashin@soleen.com, jasonmiu@google.com, Changyuan Lyu Content-Type: text/plain; charset="UTF-8" When we kexec into a new kernel from an old kernel with KHO enabled, the new kernel allocates vmemmap in the scratch area. If the KHO scratch size is too small, vmemmap allocation would fail and cause kernel panic, like the following, [ 0.027133] Faking a node at [mem 0x0000000000000000-0x00000004ffffffff] [ 0.027877] NODE_DATA(0) allocated [mem 0x4e4bd5a00-0x4e4bfffff] [ 0.029696] sparse_init_nid: node[0] memory map backing failed. Some memory will not be available. [ 0.029698] Zone ranges: [ 0.030974] DMA [mem 0x0000000000001000-0x0000000000ffffff] [ 0.031627] DMA32 [mem 0x0000000001000000-0x00000000ffffffff] [ 0.032281] Normal [mem 0x0000000100000000-0x00000004ffffffff] [ 0.032930] Device empty [ 0.033251] Movable zone start for each node [ 0.033710] Early memory node ranges [ 0.034108] node 0: [mem 0x0000000000001000-0x000000000007ffff] [ 0.034801] node 0: [mem 0x0000000000100000-0x00000000773fffff] [ 0.035461] node 0: [mem 0x0000000077400000-0x00000000775fffff] [ 0.036116] node 0: [mem 0x0000000077600000-0x000000007fffffff] [ 0.036768] node 0: [mem 0x0000000100000000-0x00000004ccbfffff] [ 0.037423] node 0: [mem 0x00000004ccc00000-0x00000004e4bfffff] [ 0.038111] BUG: kernel NULL pointer dereference, address: 0000000000000010 [ 0.038880] #PF: supervisor write access in kernel mode [ 0.039474] #PF: error_code(0x0002) - not-present page [ 0.040056] PGD 0 P4D 0 [ 0.040335] Oops: Oops: 0002 [#1] SMP [ 0.040745] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc4+ #275 NONE [ 0.041541] RIP: 0010:__bitmap_set+0x2b/0x80 [ 0.041992] Code: 0f 1e fa 55 48 89 e5 89 f1 89 f0 c1 e8 06 48 8d 04 c7 48 c7 c7 ff ff ff ff 48 d3 e7 41 89 f0 41 83 c8 c0 44 89 c6 01 d6 78 43 <48> 09 38 48 83 c0 08 83 fe 40 72 1a 41 8d 3c 10 83 c7 40 48 c7 00 [ 0.043986] RSP: 0000:ffffffff96203df0 EFLAGS: 00010047 [ 0.044546] RAX: 0000000000000010 RBX: 000000000000cc00 RCX: 0000000000000000 [ 0.045311] RDX: 0000000000000040 RSI: 0000000000000000 RDI: ffffffffffffffff [ 0.046075] RBP: ffffffff96203df0 R08: 00000000ffffffc0 R09: ffffffff9626c950 [ 0.046830] R10: 000000000002fffd R11: 0000000000000004 R12: 0000000000008000 [ 0.047574] R13: 0000000000000000 R14: 000000000000003f R15: 000000000000009b [ 0.048313] FS: 0000000000000000(0000) GS:0000000000000000(0000) knlGS:0000000000000000 [ 0.049151] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 0.049751] CR2: 0000000000000010 CR3: 00000004d123e000 CR4: 00000000000200b0 [ 0.050494] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 0.051238] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 0.051978] Call Trace: [ 0.052235] [ 0.052455] subsection_map_init+0xe4/0x130 [ 0.052891] free_area_init+0x217/0x3d0 [ 0.053290] zone_sizes_init+0x5e/0x80 [ 0.053682] paging_init+0x27/0x30 [ 0.054046] setup_arch+0x307/0x3e0 [ 0.054422] start_kernel+0x59/0x390 [ 0.054820] x86_64_start_reservations+0x28/0x30 [ 0.055307] x86_64_start_kernel+0x70/0x80 [ 0.055736] common_startup_64+0x13b/0x140 [ 0.056165] [ 0.056392] CR2: 0000000000000010 [ 0.056737] ---[ end trace 0000000000000000 ]--- [ 0.057218] RIP: 0010:__bitmap_set+0x2b/0x80 [ 0.057667] Code: 0f 1e fa 55 48 89 e5 89 f1 89 f0 c1 e8 06 48 8d 04 c7 48 c7 c7 ff ff ff ff 48 d3 e7 41 89 f0 41 83 c8 c0 44 89 c6 01 d6 78 43 <48> 09 38 48 83 c0 08 83 fe 40 72 1a 41 8d 3c 10 83 c7 40 48 c7 00 [ 0.059650] RSP: 0000:ffffffff96203df0 EFLAGS: 00010047 [ 0.060218] RAX: 0000000000000010 RBX: 000000000000cc00 RCX: 0000000000000000 [ 0.060985] RDX: 0000000000000040 RSI: 0000000000000000 RDI: ffffffffffffffff [ 0.061728] RBP: ffffffff96203df0 R08: 00000000ffffffc0 R09: ffffffff9626c950 [ 0.062486] R10: 000000000002fffd R11: 0000000000000004 R12: 0000000000008000 [ 0.063228] R13: 0000000000000000 R14: 000000000000003f R15: 000000000000009b [ 0.063968] FS: 0000000000000000(0000) GS:0000000000000000(0000) knlGS:0000000000000000 [ 0.064812] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 0.065423] CR2: 0000000000000010 CR3: 00000004d123e000 CR4: 00000000000200b0 [ 0.066175] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 0.066926] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 0.067678] Kernel panic - not syncing: Attempted to kill the idle task! [ 0.068403] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- The panic above can be easily reproduced by the following steps, 1. boot a VM with 20GiB physical memory (or larger) and kernel command line "kho=on kho_scratch=2m,256m,128m" 2. echo 1 > /sys/kernel/debug/kho/out/finalize 3. kexec to a new kernel The current panic log above is confusing and it's hard to find the root cause. Add an error log to make it easier to debug such kind of panics. Fixes: d59f43b57480 ("memblock: add support for scratch memory") Signed-off-by: Changyuan Lyu --- mm/memblock.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/memblock.c b/mm/memblock.c index 154f1d73b61f..ed886bfd3de7 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -1573,6 +1573,9 @@ phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size, goto again; } + if (flags & MEMBLOCK_KHO_SCRATCH) + pr_err_once("Could not allocate %pap bytes in KHO scratch\n", &size); + return 0; done: -- 2.49.0.1101.gccaa498523-goog