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action=none header.from=citrix.com; Date: Thu, 14 May 2026 17:30:16 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jan Beulich Cc: "xen-devel@lists.xenproject.org" , Andrew Cooper Subject: Re: [PATCH for-4.22 v2 8/8] x86/mwait-idle: Add C-states validation Message-ID: References: <178739fe-fa41-4ff7-b16e-67c4b2a99b38@suse.com> Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: BN0PR07CA0023.namprd07.prod.outlook.com (2603:10b6:408:141::6) To CH7PR03MB7860.namprd03.prod.outlook.com (2603:10b6:610:24e::14) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CH7PR03MB7860:EE_|DS0PR03MB7179:EE_ X-MS-Office365-Filtering-Correlation-Id: 50415295-9392-43d0-0321-08deb1cdb475 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|376014|366016|4143699003|18002099003|3023799003|22082099003|56012099003|11063799003; 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=?utf-8?B?WWhiTExTMUlYY09jMlRMUUlQYW1GRjRiL0JVMzhxaGhRRjFiczA4dz09?= X-OriginatorOrg: citrix.com X-MS-Exchange-CrossTenant-Network-Message-Id: 50415295-9392-43d0-0321-08deb1cdb475 X-MS-Exchange-CrossTenant-AuthSource: CH7PR03MB7860.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 May 2026 15:30:18.9519 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: Ym+g6zuwxblsUW6JFzgoZukwgnELBlyjG26KIUpyZxXAQ+xGXCyLnUJLqEkLIwlVgbrIbpsUb/QC2SyP9jz6bQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR03MB7179 X-purgate-ID: tlsNG-ebf023/1778772622-407713FF-D04EDE9D/0/0 X-purgate-type: clean X-purgate-size: 3182 On Tue, May 12, 2026 at 05:38:32PM +0200, Jan Beulich wrote: > From: Artem Bityutskiy > > Add validation for C-states specified via the "table=" module parameter. > Treat this module parameter as untrusted input and validate it thoroughly. > > Signed-off-by: Artem Bityutskiy > Link: https://patch.msgid.link/20251216080402.156988-4-dedekind1@gmail.com > Signed-off-by: Rafael J. Wysocki > Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git be6a150829b3 > > Add __init to validate_cmdline_cstate(). Other adjustments to fit our env. > > Signed-off-by: Jan Beulich Acked-by: Roger Pau Monné One comment below. > --- > v2: Const-ify validate_cmdline_cstate()'s parameters. > > --- a/xen/arch/x86/cpu/mwait-idle.c > +++ b/xen/arch/x86/cpu/mwait-idle.c > @@ -72,6 +72,11 @@ boolean_param("mwait-idle", opt_mwait_id > > /* The maximum allowed length for the 'table' module parameter */ > #define MAX_CMDLINE_TABLE_LEN 256 > +/* Maximum allowed C-state latency */ > +#define MAX_CMDLINE_LATENCY_US (5 * 1000 /* USEC_PER_MSEC */) > +/* Maximum allowed C-state target residency */ > +#define MAX_CMDLINE_RESIDENCY_US (100 * 1000 /* USEC_PER_MSEC */) > + > static char cmdline_table_str[MAX_CMDLINE_TABLE_LEN] __initdata; > string_param("mwait-idle.table", cmdline_table_str); > > @@ -1590,6 +1595,41 @@ static char *__init get_cmdline_field(ch > } > > /** > + * validate_cmdline_cstate - Validate a C-state from cmdline. > + * @state: The C-state to validate. > + * @prev_state: The previous C-state in the table or NULL. > + * > + * Return: 0 if the C-state is valid or -EINVAL otherwise. > + */ > +static int __init validate_cmdline_cstate(const struct cpuidle_state *state, > + const struct cpuidle_state *prev_state) > +{ > + if (state->exit_latency == 0) > + /* Exit latency 0 can only be used for the POLL state */ > + return -EINVAL; > + > + if (state->exit_latency > MAX_CMDLINE_LATENCY_US) > + return -EINVAL; > + > + if (state->target_residency > MAX_CMDLINE_RESIDENCY_US) > + return -EINVAL; > + > + if (state->target_residency < state->exit_latency) > + return -EINVAL; > + > + if (!prev_state) > + return 0; > + > + if (state->exit_latency <= prev_state->exit_latency) > + return -EINVAL; > + > + if (state->target_residency <= prev_state->target_residency) > + return -EINVAL; > + > + return 0; > +} > + > +/** > * cmdline_table_adjust - Adjust the C-states table with data from cmdline. > * > * Adjust the C-states table with data from the 'mwait-idle.table' parameter > @@ -1697,6 +1737,21 @@ static void __init cmdline_table_adjust( > state->name, state->exit_latency, state->target_residency); > } > > + /* Validate the adjusted C-states */ > + for (i = 0; i < state_count; i++) { > + struct cpuidle_state *prev_state; const? FWIW, you could also init the field at definition, but I understand this might diverge too much from the Linux code. Thanks, Roger.