From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B919396D35; Wed, 21 Jan 2026 18:25:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769019903; cv=none; b=CITfl2QUh4fZg+IoYMKdxgtfBkBFbloAtdWn2H6T/4jPe5i6k9J14xNKO8+M5lYYVm7RhsUXeLH8ad/vWg/9S6/HK10Tt2klJ8srLco+iW+s4bWcXE6DhG3h5bE0L+1fN8LfkE06axp7x2wNsBmdyWQbxgcgqtBpMce3zvGko+o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769019903; c=relaxed/simple; bh=cXdbeIzn3w/5hUJ53lxu5+790yZkEebBTltqCC7zNX0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=CFgSSPHePpvk0JNtgv9uHFq3sA+6cFKtzxjFGXmnQEbYPgVdUfNQ7ISPCEOhaAEY/Z2swjl6YlY4klm792EB2nUs96p4Ua51WUqzgpHlBVIdDBfo8lHVsixw7UbrsVzclaiO1KWwvafGAZHuQbuZr/wjiuawvkdkdIJUY4XPDiE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=bEkG3/Cb; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="bEkG3/Cb" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 821A0C4CEF1; Wed, 21 Jan 2026 18:25:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1769019903; bh=cXdbeIzn3w/5hUJ53lxu5+790yZkEebBTltqCC7zNX0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bEkG3/CbMf+7Q4zVy3egl31AFoz0d93IMwb3fUNil3uONcEqNzAgXAqtbQzXBE7ca U5LasbwvC/OOq9ce5Z1R5MOPmBZLzX0lKz7vwHTvUwCq6HLDyCtCCu525RMuCyXTHT bvz5TRfnyOwRUEOkmCLOSsr0m8q1zrHu3uadQZFU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Bruno Faccini , David Hildenbrand , John Hubbard , "Mike Rapoport (Microsoft)" , Zi Yan , Andrew Morton , Sasha Levin Subject: [PATCH 6.12 131/139] mm/fake-numa: allow later numa node hotplug Date: Wed, 21 Jan 2026 19:16:19 +0100 Message-ID: <20260121181416.167077132@linuxfoundation.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260121181411.452263583@linuxfoundation.org> References: <20260121181411.452263583@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Bruno Faccini [ Upstream commit 63db8170bf34ce9e0763f87d993cf9b4c9002b09 ] Current fake-numa implementation prevents new Numa nodes to be later hot-plugged by drivers. A common symptom of this limitation is the "node was absent from the node_possible_map" message by associated warning in mm/memory_hotplug.c: add_memory_resource(). This comes from the lack of remapping in both pxm_to_node_map[] and node_to_pxm_map[] tables to take fake-numa nodes into account and thus triggers collisions with original and physical nodes only-mapping that had been determined from BIOS tables. This patch fixes this by doing the necessary node-ids translation in both pxm_to_node_map[]/node_to_pxm_map[] tables. node_distance[] table has also been fixed accordingly. Details: When trying to use fake-numa feature on our system where new Numa nodes are being "hot-plugged" upon driver load, this fails with the following type of message and warning with stack : node 8 was absent from the node_possible_map WARNING: CPU: 61 PID: 4259 at mm/memory_hotplug.c:1506 add_memory_resource+0x3dc/0x418 This issue prevents the use of the fake-NUMA debug feature with the system's full configuration, when it has proven to be sometimes extremely useful for performance testing of multi-tasked, memory-bound applications, as it enables better isolation of processes/ranks compared to fat NUMA nodes. Usual numactl output after driver has “hot-plugged”/unveiled some new Numa nodes with and without memory : $ numactl --hardware available: 9 nodes (0-8) node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 0 size: 490037 MB node 0 free: 484432 MB node 1 cpus: node 1 size: 97280 MB node 1 free: 97279 MB node 2 cpus: node 2 size: 0 MB node 2 free: 0 MB node 3 cpus: node 3 size: 0 MB node 3 free: 0 MB node 4 cpus: node 4 size: 0 MB node 4 free: 0 MB node 5 cpus: node 5 size: 0 MB node 5 free: 0 MB node 6 cpus: node 6 size: 0 MB node 6 free: 0 MB node 7 cpus: node 7 size: 0 MB node 7 free: 0 MB node 8 cpus: node 8 size: 0 MB node 8 free: 0 MB node distances: node 0 1 2 3 4 5 6 7 8 0: 10 80 80 80 80 80 80 80 80 1: 80 10 255 255 255 255 255 255 255 2: 80 255 10 255 255 255 255 255 255 3: 80 255 255 10 255 255 255 255 255 4: 80 255 255 255 10 255 255 255 255 5: 80 255 255 255 255 10 255 255 255 6: 80 255 255 255 255 255 10 255 255 7: 80 255 255 255 255 255 255 10 255 8: 80 255 255 255 255 255 255 255 10 With recent M.Rapoport set of fake-numa patches in mm-everything and using numa=fake=4 boot parameter : $ numactl --hardware available: 4 nodes (0-3) node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 0 size: 122518 MB node 0 free: 117141 MB node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 1 size: 219911 MB node 1 free: 219751 MB node 2 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 2 size: 122599 MB node 2 free: 122541 MB node 3 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 3 size: 122479 MB node 3 free: 122408 MB node distances: node 0 1 2 3 0: 10 10 10 10 1: 10 10 10 10 2: 10 10 10 10 3: 10 10 10 10 With recent M.Rapoport set of fake-numa patches in mm-everything, this patch on top, using numa=fake=4 boot parameter : # numactl —hardware available: 12 nodes (0-11) node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 0 size: 122518 MB node 0 free: 116429 MB node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 1 size: 122631 MB node 1 free: 122576 MB node 2 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 2 size: 122599 MB node 2 free: 122544 MB node 3 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 node 3 size: 122479 MB node 3 free: 122419 MB node 4 cpus: node 4 size: 97280 MB node 4 free: 97279 MB node 5 cpus: node 5 size: 0 MB node 5 free: 0 MB node 6 cpus: node 6 size: 0 MB node 6 free: 0 MB node 7 cpus: node 7 size: 0 MB node 7 free: 0 MB node 8 cpus: node 8 size: 0 MB node 8 free: 0 MB node 9 cpus: node 9 size: 0 MB node 9 free: 0 MB node 10 cpus: node 10 size: 0 MB node 10 free: 0 MB node 11 cpus: node 11 size: 0 MB node 11 free: 0 MB node distances: node 0 1 2 3 4 5 6 7 8 9 10 11 0: 10 10 10 10 80 80 80 80 80 80 80 80 1: 10 10 10 10 80 80 80 80 80 80 80 80 2: 10 10 10 10 80 80 80 80 80 80 80 80 3: 10 10 10 10 80 80 80 80 80 80 80 80 4: 80 80 80 80 10 255 255 255 255 255 255 255 5: 80 80 80 80 255 10 255 255 255 255 255 255 6: 80 80 80 80 255 255 10 255 255 255 255 255 7: 80 80 80 80 255 255 255 10 255 255 255 255 8: 80 80 80 80 255 255 255 255 10 255 255 255 9: 80 80 80 80 255 255 255 255 255 10 255 255 10: 80 80 80 80 255 255 255 255 255 255 10 255 11: 80 80 80 80 255 255 255 255 255 255 255 10 Link: https://lkml.kernel.org/r/20250106120659.359610-2-bfaccini@nvidia.com Signed-off-by: Bruno Faccini Cc: David Hildenbrand Cc: John Hubbard Cc: Mike Rapoport (Microsoft) Cc: Zi Yan Signed-off-by: Andrew Morton Stable-dep-of: f46c26f1bcd9 ("mm: numa,memblock: include for 'numa_nodes_parsed'") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/acpi/numa/srat.c | 86 +++++++++++++++++++++++++++++++++++++++++++ include/acpi/acpi_numa.h | 5 ++ include/linux/numa_memblks.h | 3 + mm/numa_emulation.c | 45 +++++++++++++++++++--- mm/numa_memblks.c | 2 - 5 files changed, 133 insertions(+), 8 deletions(-) --- a/drivers/acpi/numa/srat.c +++ b/drivers/acpi/numa/srat.c @@ -81,6 +81,92 @@ int acpi_map_pxm_to_node(int pxm) } EXPORT_SYMBOL(acpi_map_pxm_to_node); +#ifdef CONFIG_NUMA_EMU +/* + * Take max_nid - 1 fake-numa nodes into account in both + * pxm_to_node_map()/node_to_pxm_map[] tables. + */ +int __init fix_pxm_node_maps(int max_nid) +{ + static int pxm_to_node_map_copy[MAX_PXM_DOMAINS] __initdata + = { [0 ... MAX_PXM_DOMAINS - 1] = NUMA_NO_NODE }; + static int node_to_pxm_map_copy[MAX_NUMNODES] __initdata + = { [0 ... MAX_NUMNODES - 1] = PXM_INVAL }; + int i, j, index = -1, count = 0; + nodemask_t nodes_to_enable; + + if (numa_off || srat_disabled()) + return -1; + + /* find fake nodes PXM mapping */ + for (i = 0; i < MAX_NUMNODES; i++) { + if (node_to_pxm_map[i] != PXM_INVAL) { + for (j = 0; j <= max_nid; j++) { + if ((emu_nid_to_phys[j] == i) && + WARN(node_to_pxm_map_copy[j] != PXM_INVAL, + "Node %d is already binded to PXM %d\n", + j, node_to_pxm_map_copy[j])) + return -1; + if (emu_nid_to_phys[j] == i) { + node_to_pxm_map_copy[j] = + node_to_pxm_map[i]; + if (j > index) + index = j; + count++; + } + } + } + } + if (WARN(index != max_nid, "%d max nid when expected %d\n", + index, max_nid)) + return -1; + + nodes_clear(nodes_to_enable); + + /* map phys nodes not used for fake nodes */ + for (i = 0; i < MAX_NUMNODES; i++) { + if (node_to_pxm_map[i] != PXM_INVAL) { + for (j = 0; j <= max_nid; j++) + if (emu_nid_to_phys[j] == i) + break; + /* fake nodes PXM mapping has been done */ + if (j <= max_nid) + continue; + /* find first hole */ + for (j = 0; + j < MAX_NUMNODES && + node_to_pxm_map_copy[j] != PXM_INVAL; + j++) + ; + if (WARN(j == MAX_NUMNODES, + "Number of nodes exceeds MAX_NUMNODES\n")) + return -1; + node_to_pxm_map_copy[j] = node_to_pxm_map[i]; + node_set(j, nodes_to_enable); + count++; + } + } + + /* creating reverse mapping in pxm_to_node_map[] */ + for (i = 0; i < MAX_NUMNODES; i++) + if (node_to_pxm_map_copy[i] != PXM_INVAL && + pxm_to_node_map_copy[node_to_pxm_map_copy[i]] == NUMA_NO_NODE) + pxm_to_node_map_copy[node_to_pxm_map_copy[i]] = i; + + /* overwrite with new mapping */ + for (i = 0; i < MAX_NUMNODES; i++) { + node_to_pxm_map[i] = node_to_pxm_map_copy[i]; + pxm_to_node_map[i] = pxm_to_node_map_copy[i]; + } + + /* enable other nodes found in PXM for hotplug */ + nodes_or(numa_nodes_parsed, nodes_to_enable, numa_nodes_parsed); + + pr_debug("found %d total number of nodes\n", count); + return 0; +} +#endif + static void __init acpi_table_print_srat_entry(struct acpi_subtable_header *header) { --- a/include/acpi/acpi_numa.h +++ b/include/acpi/acpi_numa.h @@ -17,11 +17,16 @@ extern int node_to_pxm(int); extern int acpi_map_pxm_to_node(int); extern unsigned char acpi_srat_revision; extern void disable_srat(void); +extern int fix_pxm_node_maps(int max_nid); extern void bad_srat(void); extern int srat_disabled(void); #else /* CONFIG_ACPI_NUMA */ +static inline int fix_pxm_node_maps(int max_nid) +{ + return 0; +} static inline void disable_srat(void) { } --- a/include/linux/numa_memblks.h +++ b/include/linux/numa_memblks.h @@ -29,7 +29,10 @@ int __init numa_cleanup_meminfo(struct n int __init numa_memblks_init(int (*init_func)(void), bool memblock_force_top_down); +extern int numa_distance_cnt; + #ifdef CONFIG_NUMA_EMU +extern int emu_nid_to_phys[MAX_NUMNODES]; int numa_emu_cmdline(char *str); void __init numa_emu_update_cpu_to_node(int *emu_nid_to_phys, unsigned int nr_emu_nids); --- a/mm/numa_emulation.c +++ b/mm/numa_emulation.c @@ -8,11 +8,12 @@ #include #include #include +#include #define FAKE_NODE_MIN_SIZE ((u64)32 << 20) #define FAKE_NODE_MIN_HASH_MASK (~(FAKE_NODE_MIN_SIZE - 1UL)) -static int emu_nid_to_phys[MAX_NUMNODES]; +int emu_nid_to_phys[MAX_NUMNODES]; static char *emu_cmdline __initdata; int __init numa_emu_cmdline(char *str) @@ -379,6 +380,7 @@ void __init numa_emulation(struct numa_m size_t phys_size = numa_dist_cnt * numa_dist_cnt * sizeof(phys_dist[0]); int max_emu_nid, dfl_phys_nid; int i, j, ret; + nodemask_t physnode_mask = numa_nodes_parsed; if (!emu_cmdline) goto no_emu; @@ -395,7 +397,6 @@ void __init numa_emulation(struct numa_m * split the system RAM into N fake nodes. */ if (strchr(emu_cmdline, 'U')) { - nodemask_t physnode_mask = numa_nodes_parsed; unsigned long n; int nid = 0; @@ -465,9 +466,6 @@ void __init numa_emulation(struct numa_m */ max_emu_nid = setup_emu2phys_nid(&dfl_phys_nid); - /* commit */ - *numa_meminfo = ei; - /* Make sure numa_nodes_parsed only contains emulated nodes */ nodes_clear(numa_nodes_parsed); for (i = 0; i < ARRAY_SIZE(ei.blk); i++) @@ -475,10 +473,21 @@ void __init numa_emulation(struct numa_m ei.blk[i].nid != NUMA_NO_NODE) node_set(ei.blk[i].nid, numa_nodes_parsed); - numa_emu_update_cpu_to_node(emu_nid_to_phys, ARRAY_SIZE(emu_nid_to_phys)); + /* fix pxm_to_node_map[] and node_to_pxm_map[] to avoid collision + * with faked numa nodes, particularly during later memory hotplug + * handling, and also update numa_nodes_parsed accordingly. + */ + ret = fix_pxm_node_maps(max_emu_nid); + if (ret < 0) + goto no_emu; + + /* commit */ + *numa_meminfo = ei; + + numa_emu_update_cpu_to_node(emu_nid_to_phys, max_emu_nid + 1); /* make sure all emulated nodes are mapped to a physical node */ - for (i = 0; i < ARRAY_SIZE(emu_nid_to_phys); i++) + for (i = 0; i < max_emu_nid + 1; i++) if (emu_nid_to_phys[i] == NUMA_NO_NODE) emu_nid_to_phys[i] = dfl_phys_nid; @@ -501,12 +510,34 @@ void __init numa_emulation(struct numa_m numa_set_distance(i, j, dist); } } + for (i = 0; i < numa_distance_cnt; i++) { + for (j = 0; j < numa_distance_cnt; j++) { + int physi, physj; + u8 dist; + + /* distance between fake nodes is already ok */ + if (emu_nid_to_phys[i] != NUMA_NO_NODE && + emu_nid_to_phys[j] != NUMA_NO_NODE) + continue; + if (emu_nid_to_phys[i] != NUMA_NO_NODE) + physi = emu_nid_to_phys[i]; + else + physi = i - max_emu_nid; + if (emu_nid_to_phys[j] != NUMA_NO_NODE) + physj = emu_nid_to_phys[j]; + else + physj = j - max_emu_nid; + dist = phys_dist[physi * numa_dist_cnt + physj]; + numa_set_distance(i, j, dist); + } + } /* free the copied physical distance table */ memblock_free(phys_dist, phys_size); return; no_emu: + numa_nodes_parsed = physnode_mask; /* No emulation. Build identity emu_nid_to_phys[] for numa_add_cpu() */ for (i = 0; i < ARRAY_SIZE(emu_nid_to_phys); i++) emu_nid_to_phys[i] = i; --- a/mm/numa_memblks.c +++ b/mm/numa_memblks.c @@ -7,7 +7,7 @@ #include #include -static int numa_distance_cnt; +int numa_distance_cnt; static u8 *numa_distance; nodemask_t numa_nodes_parsed __initdata;