Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH 2/2] xen: reset legacy rtc flag for PV domU
To:     Juergen Gross <jgross@suse.com>, xen-devel@lists.xenproject.org,
        x86@kernel.org, linux-kernel@vger.kernel.org
Cc:     Stefano Stabellini <sstabellini@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, stable@vger.kernel.org
References: <20210903084937.19392-1-jgross@suse.com>
 <20210903084937.19392-3-jgross@suse.com>
From:   Boris Ostrovsky <boris.ostrovsky@oracle.com>
Message-ID: <b2cd2936-7ec4-e0b2-458e-51c12a3f56aa@oracle.com>
Date:   Wed, 8 Sep 2021 10:54:07 -0400
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0)
 Gecko/20100101 Thunderbird/78.14.0
In-Reply-To: <20210903084937.19392-3-jgross@suse.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Content-Language: en-US
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?NmJ3WmE2ZjVaUE15TUFiVFFQV2dvUTFiY3RIc3M2RGNlTEcxNlBjMDdwenkv?=
 =?utf-8?B?aXl6enFldUJ3YTVXRWVCVFo1aUNCNzNuU1Y0ZFBqakxoRWVETG9paEFKdGZU?=
 =?utf-8?B?QUF3T1F2SVNKVy81YnlLSEV4SG9OK1U0czZBYlQxS3hKNElZTlNhdTVORVMv?=
 =?utf-8?B?ZDJpVjdaamJWL1F3R0VmdzRJQVVjeno2K2Y4bzVuZ0lRcXJQajB5dUw1MktW?=
 =?utf-8?B?ZkxRenc1TlVtRGc1RWk3TTFXS2c2L0hTVC82MDRnR3hjTG5tVFI4ZndjeWx2?=
 =?utf-8?B?Z0VGV1IveGVRYnZrL1R1UzIwb1MzQ0FVMTh4QldaNHhzdlh5dnh5Si81OVk1?=
 =?utf-8?B?Zk91NzIxVkd0VC9GTXMveXNxQjZ2cVdTeGpiTWxweFF0REZ5MjNXWmEvNUZ1?=
 =?utf-8?B?VHNMZjdMOUs1Uk12MDVBUTZrRnRRQ2F1R0diS1g3Y2lXMk1wV0Nta1ZtNkJW?=
 =?utf-8?B?VlJ6cEFiaGppdWFHcWNHbWlxTlhnUk1EZm8vYWh6eVlEcFFVZTJKUis3RlZn?=
 =?utf-8?B?K3gvbkdNYUV6MWFEcWZtdlRsRks0dTgzejBncGg5WC80VkJ4bm82WHFrc1BK?=
 =?utf-8?B?bkdRSDZaWkdScVJSeVAyL3lmOUpMYmlwVnI0Q2V0YjdGdGhnMzFnc2YvQ0FD?=
 =?utf-8?B?ODNmQlJFWjI1Wm5MeDhnaWxMZzltY1UrVVNWQVpLMnh5akN1K3gwZFU4ZmZI?=
 =?utf-8?B?QWlIRWt4amFyU1dXd0pRRjFIb2E4TXd4ZHl4NGlaQXpOTCt0bysrTk1LVzBG?=
 =?utf-8?B?S3FSTWN1QW1wWWZTWmFOVGhpbzFxejYzOHp3U2pLS3g3MUZHejlGTzllWFky?=
 =?utf-8?B?ekozKzhBcllQUzhzT29EeGM1YTdTdlhRSVFUR3FwZm9BQ2JicUxQbm9xa05R?=
 =?utf-8?B?dGZreElZWVBkY1BiRGZ6RC9zb2dORjlwYmVHc1R6N1RId3pMVVpYL1ZmNEdW?=
 =?utf-8?B?eFlEZFJ5ZnpNaXJPMUc2VUkwUUxaZWZZM1dYcjgwcU5GeUFWM3hwOTVsTFJh?=
 =?utf-8?B?dzZSU1NwdlNPbWFxZWJCTkl2anBMV2FueGxSUnREZWdqM1VUQXFUWXVBdzBW?=
 =?utf-8?B?ZU56bnJjT0dtajlmazRuSXlXQ2NWMkhWQk9lVU10eDV6T05OdlREN284Q0VR?=
 =?utf-8?B?b2NKNWtFMFFUc2FiYVRDa2ZwMmgzaVM5WDNaYmhlc3BNQTlJam1QTFc1TEdB?=
 =?utf-8?B?UE5ZODI2Qy9WeVNBM1dOTEJwZ01XUDVrakM3TGhXVzlTYlViOE11RjV0SjRY?=
 =?utf-8?B?ZGdsTHpPTEx3QXl6dEdkRWNQcUl6VXNBRG1reUtKVHZpRWlKek5iNmJFN0dV?=
 =?utf-8?B?bngySEZQVVVzNmw2UnpkSFg2RUVCejEzSDdPazBPQTdpS25zVkV3bzRMU1RF?=
 =?utf-8?B?NjRlbGpSUWVOcG82dXJMYWQrT01UYTBPbDlDaDFVcHhCWXhmZFlES2tlWUVC?=
 =?utf-8?B?YkYxTjl3QmlLLzBLaHFRbGxFc0g3d1NwS1RMR3RWZWlEb2VmelRCZlVydjBo?=
 =?utf-8?B?eDEwR29jQUZWZHR5NmttdE5UVDRIUEk2bWNSREEwWFRGeWFyOEloczdNNUpp?=
 =?utf-8?B?NXY4VVl6WnJwbytvRzdTLzlzcENiZU5xRkhqS3pRUXRLeGhoVXZyaVRTK1Ux?=
 =?utf-8?B?dnpLS1BBQkNvOWdrVnNDd295T1VXcnJ0WEd1VXNHQWZVc3E2TGtibjFpclY1?=
 =?utf-8?B?NnJXNmI1bFVmU29VREl1aUdpSWRBNnp3endIN0RJNU8yN1FoLyswS2xJdWVK?=
 =?utf-8?Q?RolcjRs08WzEtLzjiX//bpizM7Ep4Jk4NIYKF2y?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 9c67d3e7-3179-4284-7f7a-08d972d88477
X-MS-Exchange-CrossTenant-AuthSource: BLAPR10MB5009.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2021 14:54:11.2224
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: bRLXF+EPkNc+8N4+wrckUmzNzw6wmUKX47qx1iM1qj71KHEXpzkBfkpVqixhoI4FZdeCcSKvzyMkI1AsP0rVnUWo1EHuAJarqO9Fle6pkXQ=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL0PR10MB3444
X-Proofpoint-Virus-Version: vendor=nai engine=6300 definitions=10101 signatures=668682
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 phishscore=0 bulkscore=0
 mlxlogscore=999 malwarescore=0 spamscore=0 mlxscore=0 suspectscore=0
 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2109030001 definitions=main-2109080093
X-Proofpoint-GUID: 7U7S6iHGs1PIrquqq2ApWZHCvSLEFWlN
X-Proofpoint-ORIG-GUID: 7U7S6iHGs1PIrquqq2ApWZHCvSLEFWlN
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On 9/3/21 4:49 AM, Juergen Gross wrote:
> A Xen PV guest doesn't have a legacy RTC device, so reset the legacy
> RTC flag. Otherwise the following WARN splat will occur at boot:
>
> [    1.333404] WARNING: CPU: 1 PID: 1 at /home/gross/linux/head/drivers/rtc/rtc-mc146818-lib.c:25 mc146818_get_time+0x1be/0x210
> [    1.333404] Modules linked in:
> [    1.333404] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W         5.14.0-rc7-default+ #282
> [    1.333404] RIP: e030:mc146818_get_time+0x1be/0x210
> [    1.333404] Code: c0 64 01 c5 83 fd 45 89 6b 14 7f 06 83 c5 64 89 6b 14 41 83 ec 01 b8 02 00 00 00 44 89 63 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3 <0f> 0b 48 c7 c7 30 0e ef 82 4c 89 e6 e8 71 2a 24 00 48 c7 c0 ff ff
> [    1.333404] RSP: e02b:ffffc90040093df8 EFLAGS: 00010002
> [    1.333404] RAX: 00000000000000ff RBX: ffffc90040093e34 RCX: 0000000000000000
> [    1.333404] RDX: 0000000000000001 RSI: 0000000000000000 RDI: 000000000000000d
> [    1.333404] RBP: ffffffff82ef0e30 R08: ffff888005013e60 R09: 0000000000000000
> [    1.333404] R10: ffffffff82373e9b R11: 0000000000033080 R12: 0000000000000200
> [    1.333404] R13: 0000000000000000 R14: 0000000000000002 R15: ffffffff82cdc6d4
> [    1.333404] FS:  0000000000000000(0000) GS:ffff88807d440000(0000) knlGS:0000000000000000
> [    1.333404] CS:  10000e030 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    1.333404] CR2: 0000000000000000 CR3: 000000000260a000 CR4: 0000000000050660
> [    1.333404] Call Trace:
> [    1.333404]  ? wakeup_sources_sysfs_init+0x30/0x30
> [    1.333404]  ? rdinit_setup+0x2b/0x2b
> [    1.333404]  early_resume_init+0x23/0xa4
> [    1.333404]  ? cn_proc_init+0x36/0x36
> [    1.333404]  do_one_initcall+0x3e/0x200
> [    1.333404]  kernel_init_freeable+0x232/0x28e
> [    1.333404]  ? rest_init+0xd0/0xd0
> [    1.333404]  kernel_init+0x16/0x120
> [    1.333404]  ret_from_fork+0x1f/0x30
>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Juergen Gross <jgross@suse.com>


Fixes: 211e5db19d15 ("rtc: mc146818: Detect and handle broken RTCs") ?


Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>