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Message-ID: <3a455e81-6db1-be47-42f1-9aa49531d715@suse.com> Date: Fri, 3 Mar 2023 08:31:38 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Content-Language: en-US To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , Wei Liu , =?utf-8?q?Roger_Pau_Monn=C3=A9?= , George Dunlap , Kevin Tian , Jun Nakajima From: Jan Beulich Subject: [PATCH] x86/altp2m: help gcc13 to avoid it emitting a warning X-ClientProxiedBy: FR2P281CA0182.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:9f::10) To VE1PR04MB6560.eurprd04.prod.outlook.com (2603:10a6:803:122::25) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: VE1PR04MB6560:EE_|DB9PR04MB8073:EE_ X-MS-Office365-Filtering-Correlation-Id: b58a69f4-ecf5-4e1d-cf2a-08db1bb95485 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VE1PR04MB6560.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230025)(39860400002)(376002)(346002)(366004)(136003)(396003)(451199018)(31686004)(5660300002)(4326008)(41300700001)(36756003)(83380400001)(66556008)(66946007)(66476007)(2906002)(316002)(8676002)(8936002)(6916009)(6486002)(38100700002)(186003)(6506007)(31696002)(6512007)(2616005)(478600001)(26005)(86362001)(54906003)(43740500002)(45980500001);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?q?ToLEOiQen1uGrfHOyJ7mkhqrbAEW?= =?utf-8?q?ZKT77mY6DTxX4+gLuoXzDqXIHn8R9U4N/LuupifdAfBYrUx01j74f+tDq+TC1uSMk?= =?utf-8?q?3OZLijtmKZTCV2nFfEwHrobyg2/d+j6GE7TYAiWcC/uwxmPqqzPb0sbpQhFCSBA3H?= =?utf-8?q?n8T1gbLY+V5yKEpvUrIOMQvoqUsoJRHWf6KWae+BBVfylENY1CuXW6hLW3G6mk6Yi?= =?utf-8?q?pqdg4qqvjh1j4lJMkIyUBfOspdtClitS3vvysrZemV/9J8HMLZBuhD/Y4ureG6lMg?= =?utf-8?q?Gs1XvCg9RSCUKodrl4Py/Z1j2d//DjU8N/xmb+9okxTBN8qehETfJJUr8H1AZChTN?= =?utf-8?q?JZ98Udw8SkxZ8+zoQQvaHt33surIl7AXGThU/KLjlI7oXHSHBaVk0vZD0bmoPYAlS?= =?utf-8?q?ekJ9RtNM4xo4M6mG9WPv2tLyuET5c0zzi0jbVaEBock3ksVNO1q3gV72V50TzDzd2?= =?utf-8?q?EBSLIAR1zEdVT84RxjLnfY2o9RMGsEsuqh49/TT/C6loI1Am6wXxDNV+ejXcIki4g?= =?utf-8?q?IG4CYKHe6tbb9u7LQ17YnF9YJLTd9C8RKZ8ZIP8ky/+WlU7KaQsjr6C4Nxm8+qyfJ?= =?utf-8?q?SKgsr0TDSZ5t7KvIw2E7+/QtWPKTWU7t3IFdDorjQhNGjwOLXTTcKC1sWeLJ2iUZM?= =?utf-8?q?MlfX6Dsnv9M4uaH0odbbxB7molIykh9f89YHUAg9GWPCgU2HPeMvs6/lb+fj7Eu72?= =?utf-8?q?tNIB8biwFZ049mSqAxSuar8kF6a3LGtY5OqqE203LfNrTFWfz5Kp5ywFq0/lYDLE8?= =?utf-8?q?UVhGDf5TIyeqtNYWExRbZ2wgyvtZdLEUtZi6ykahQO6YGAsTeSjAJ5c/NCuG/txrL?= =?utf-8?q?D8FNgHULDGCqEd+5wrkpSpYb/hMGJHHaYGuQ4ZjxPN/8xGyu064+5FYLV7P1cXRky?= =?utf-8?q?3w0CBa+VxHWhnWF+aWCRIR1tQZUO5uDD7TSY/irAgIxlPJ1DMwtGc68wvAbQQxc9H?= =?utf-8?q?Tu06KJQ2DQp1FcPJBKNy/mVcmw8K9eNHuM/ih48Zqq50QkmhN3ABtnh0TjVgtNfhe?= =?utf-8?q?DwV3aO/LJVVMi8Ykuy5AVGjkoeoAcukAUukUagKIR+DYH57S5//S8H5oKoUIQGT8o?= =?utf-8?q?4wPJuEQ5ssiP/tQzSTxeEAZKqGn1rJhN2iOe4Ve96BCfpXdiDGGE1k7ARETOtPCUF?= =?utf-8?q?RIL6K4JEqMTv32cH7tlOs53ay1sevHruNmYQpWJoZyw2RQpXmNW49+8DQSi1rLigK?= =?utf-8?q?d+drB2YWEhfU36AJbEV4IsK8LLhkN1f5sjNFgLPaKM1Pc6HJiCIuRyKLclQ2q92Gh?= =?utf-8?q?FWEOP9DSd8W1mOiecN430p1hulVP7CtCV4AFjcrPNcf1tD0UQD6j8qcaNIERM6Aw5?= =?utf-8?q?E6Fy9W0CwDONim7ExHNgDvaYg9AoSqABNM0XtTsCB0A0y1V49v0r51ZMO725p4Wi1?= =?utf-8?q?V97LFEmqgPY3mqpPzuCSiLKOqY5yptV1IgtHEFTUiaJ95E99kSsLJ2ZZWJRiW3ei7?= =?utf-8?q?pOOgJiUdQkwBcpWvBBNIxKxhay/w0mrjx2vlixSp4pJ8ItbTukbrlkjVNpXGsievK?= =?utf-8?q?/BLEVFWdJBjp?= X-OriginatorOrg: suse.com X-MS-Exchange-CrossTenant-Network-Message-Id: b58a69f4-ecf5-4e1d-cf2a-08db1bb95485 X-MS-Exchange-CrossTenant-AuthSource: VE1PR04MB6560.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Mar 2023 07:31:40.5106 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: uXxlcHujF+/J1cAMm5HdWwlnZGcmMtKByR49lA5a0HBPxpaV/4O97cwyIjfrdYVR1jlWYV1elGbiw5YYC9URtA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB9PR04MB8073 Switches of altp2m-s always expect a valid altp2m to be in place (and indeed altp2m_vcpu_initialise() sets the active one to be at index 0). The compiler, however, cannot know that, and hence it cannot eliminate p2m_get_altp2m()'s case of returnin (literal) NULL. If then the compiler decides to special case that code path in the caller, the dereference in instances of atomic_dec(&p2m_get_altp2m(v)->active_vcpus); can, to the code generator, appear to be NULL dereferences, leading to In function 'atomic_dec', inlined from '...' at ...: ./arch/x86/include/asm/atomic.h:182:5: error: array subscript 0 is outside array bounds of 'int[0]' [-Werror=array-bounds=] Aid the compiler by adding a BUG_ON() checking the return value of the problematic p2m_get_altp2m(). Since with the use of the local variable the 2nd p2m_get_altp2m() each will look questionable at the first glance (Why is the local variable not used here?), open-code the only relevant piece of p2m_get_altp2m() there. To avoid repeatedly doing these transformations, and also to limit how "bad" the open-coding really is, convert the entire operation to an inline helper, used by all three instances (and accepting the redundant BUG_ON(idx >= MAX_ALTP2M) in two of the three cases). Reported-by: Charles Arnold Signed-off-by: Jan Beulich Acked-by: Andrew Cooper Reviewed-by: Kevin Tian --- a/xen/arch/x86/hvm/vmx/vmx.c +++ b/xen/arch/x86/hvm/vmx/vmx.c @@ -4128,13 +4128,7 @@ void vmx_vmexit_handler(struct cpu_user_ } } - if ( idx != vcpu_altp2m(v).p2midx ) - { - BUG_ON(idx >= MAX_ALTP2M); - atomic_dec(&p2m_get_altp2m(v)->active_vcpus); - vcpu_altp2m(v).p2midx = idx; - atomic_inc(&p2m_get_altp2m(v)->active_vcpus); - } + p2m_set_altp2m(v, idx); } if ( unlikely(currd->arch.monitor.vmexit_enabled) ) --- a/xen/arch/x86/include/asm/p2m.h +++ b/xen/arch/x86/include/asm/p2m.h @@ -879,6 +879,26 @@ static inline struct p2m_domain *p2m_get return v->domain->arch.altp2m_p2m[index]; } +/* set current alternate p2m table */ +static inline bool p2m_set_altp2m(struct vcpu *v, unsigned int idx) +{ + struct p2m_domain *orig; + + BUG_ON(idx >= MAX_ALTP2M); + + if ( idx == vcpu_altp2m(v).p2midx ) + return false; + + orig = p2m_get_altp2m(v); + BUG_ON(!orig); + atomic_dec(&orig->active_vcpus); + + vcpu_altp2m(v).p2midx = idx; + atomic_inc(&v->domain->arch.altp2m_p2m[idx]->active_vcpus); + + return true; +} + /* Switch alternate p2m for a single vcpu */ bool_t p2m_switch_vcpu_altp2m_by_id(struct vcpu *v, unsigned int idx); --- a/xen/arch/x86/mm/p2m.c +++ b/xen/arch/x86/mm/p2m.c @@ -1789,13 +1789,8 @@ bool_t p2m_switch_vcpu_altp2m_by_id(stru if ( d->arch.altp2m_eptp[idx] != mfn_x(INVALID_MFN) ) { - if ( idx != vcpu_altp2m(v).p2midx ) - { - atomic_dec(&p2m_get_altp2m(v)->active_vcpus); - vcpu_altp2m(v).p2midx = idx; - atomic_inc(&p2m_get_altp2m(v)->active_vcpus); + if ( p2m_set_altp2m(v, idx) ) altp2m_vcpu_update_p2m(v); - } rc = 1; } @@ -2072,13 +2067,8 @@ int p2m_switch_domain_altp2m_by_id(struc if ( d->arch.altp2m_visible_eptp[idx] != mfn_x(INVALID_MFN) ) { for_each_vcpu( d, v ) - if ( idx != vcpu_altp2m(v).p2midx ) - { - atomic_dec(&p2m_get_altp2m(v)->active_vcpus); - vcpu_altp2m(v).p2midx = idx; - atomic_inc(&p2m_get_altp2m(v)->active_vcpus); + if ( p2m_set_altp2m(v, idx) ) altp2m_vcpu_update_p2m(v); - } rc = 0; }