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mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.onmicrosoft.com; s=selector2-citrix-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=+n979Kpzz3wOb0UKzWhsUCl9o6Pi8vFOEIIokHfCfXo=; b=H4aX7pdMZ+oUNOpGURL8a6MRFuEMcR/7eTKn80JTrq4jIk32vWyEnbSEU00/VkTyUh9T4Ab21wwZDUfwJEaYOBucbFHtiylppw1/2RBMNS0CyMcPl+ApbxzCVV7IGRoUNzWKBDgrViqgwGO79aGo4DLaZFdhwgyCVh8mBmTks2U= Subject: Re: [PATCH RFC for-4.15] x86/msr: introduce an option for legacy MSR behavior selection From: Andrew Cooper To: Boris Ostrovsky , Roger Pau Monne , CC: Ian Jackson , Wei Liu , Anthony PERARD , Jan Beulich , Jun Nakajima , Kevin Tian References: <20210301162357.76527-1-roger.pau@citrix.com> Message-ID: <9e679925-5d1c-3a43-10ff-dba1bd2ddff9@citrix.com> Date: Thu, 4 Mar 2021 14:17:59 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?YXIyT1dtVkpHU291SmdUWTZnbURhTllNUmJ5dndMajB4WmhOdjQ4bDl5ZWo3?= =?utf-8?B?UVhuSWJ2REx0YjFVL0YxQmc4bkRhamlHNjlxMUhWSmFaNjdHck1WL2daRnNU?= =?utf-8?B?RW51bWk2UlNhaVZmejdqMnhEL0toWE9JVEF0OThlWStHdGpoN05WZ3BLMS9k?= =?utf-8?B?Z0lwTi96NmprdVJ0cUxJUFM3akZxakZsQVdvcW5SUkh3eEsrWkhmQmxBQ0ox?= =?utf-8?B?NjVkUEVzWURIYUFrTzJMQVFUREZFZXExaTBST2ZGYTBVSkxic0dyUlBQeVRw?= =?utf-8?B?ZFRGdHRocW1tSlVuemNCVlNabnVvRnNielFwSm1xMTJxRW9tNWNiWlFteFh4?= =?utf-8?B?aXRUSzl4OGRXNmQvRUJjS2VnMmlzUVFpbUlWcjgzcEdJdVJyWnNIOWZGZ004?= =?utf-8?B?dHFjSVZzSEJDMHZBM3dPdnRXMWNUbmgzYUVaSVZ1MERBWlZnUURLUDJGS1Aw?= =?utf-8?B?SkFwMkJBemp2N1ZvdDVPUGROZFNEM2V6QW1hVDFwMDV3clcwQWo2L0tkSXFu?= =?utf-8?B?cFN3dlhRWXg2TlNpeGxhNlRrK25aTlp3Mk1hMld5UVhRS3ZrTVJSY0pGS3BS?= =?utf-8?B?SUp5eGlNVjIvcVcxbDc5aDQzb2xxZmVWMGhaUm03aUVNdVg3aHpKaFd1QlB6?= =?utf-8?B?UTQ2VkprNjl1WTVlcHBRUFoxbHlMa2djOGZuNkVxc3VsSlBqckdXM3NVS0lS?= =?utf-8?B?R1dFWDlZWjlhWDBYbkFGRTVhTkt4NmZSK0RLVWdYSDg0ejdkZ2x1OTlWbzZO?= =?utf-8?B?T29wM1BFM2k2RDlSUjZkblRERk9Jc2puVW9IV0JjcVZRTUFRWUpzTmNtN1BI?= =?utf-8?B?Qjk5cW1qU1hDak50TW0yTUQza1l5Z1VvU25oOVRZY0tCMlpnaXRUZGdxcUJR?= =?utf-8?B?MVBlSEtqLzdyZDV6cDNtWjlkTEU3dUhpcjFUR0pYWW56cDAwaWZYT0FXbkJy?= =?utf-8?B?RURMUEtwbmJjOFpvSHNBV3FxZ0R6ZkwySTJIMWN6bk9ZS1RnQzh5V2IwV3da?= =?utf-8?B?Zk1XejRGMWJsWjdFNGlxeGdmNWZWV1JvazByRm13SFFWTnZzL2dicHNYdWpL?= =?utf-8?B?Ui8xR1hqSFBjaEVud3o1ZHp3dlZqZWU4b2lBM3ZqbWkwajRyVE1OcXpESWZU?= =?utf-8?B?SUllV1RWVHB2L1lxSTFvbm9jbmVCR2NxZjdFOTgxcjB3SVY2N0dGK3M0VWpK?= =?utf-8?B?YnZHWXVpeGllQXF4Ull0U1Q1aEZqQWZxdGNpRmMza0pyTmNUZDFKRlV1RUwv?= =?utf-8?B?RG5VQm43c29jK2NaaDZsUlB2OVVJYmlHelF5T1gzMjlscGhQMUtpQzQzUVAv?= =?utf-8?B?Qy9VVko0bW9adGdQQ3hxa0JMWm1FYWNObVRMenpoY3AyWVd6OHNKWGdRQjFX?= =?utf-8?B?RkVMQk0vZUNNZDdEZUVuSmxwendQS0drMEY1cFl3Yyt2RkpuOWVsVTZwSWVu?= =?utf-8?B?UzJRRUw3YS9vbStqNlFQRmkrZ2ovbVFSczMxeFRKZGFqeUFIVksvVjV3YUR3?= =?utf-8?B?ZlpjdGRVWmRUeXlpS2xaNGY2K2RVOWRudWlCQW4vQlVrc000Z2xhSzBUa1ZY?= =?utf-8?B?dS9zcEdmd2F6T0g4bW1hVnFpbmhCYUVKYzdzVmRzUzZBcGJ6TmVOck1UQktY?= =?utf-8?B?SHlOY3lQYW43dk9sSVNMaTE2eHNFT2FZWFptY2NuRlhtT1lGbXpTc2lsNWdI?= =?utf-8?B?L3NOMHpXQnNIRzVJTjRCaVIrN3pPT21kRjdVNGVueUxVYklXQ1U1cm9xV3Q0?= =?utf-8?Q?wvbCN3YOlpj5VI+r3/gRcz4oNxxvCVEUNu3obrU?= X-MS-Exchange-CrossTenant-Network-Message-Id: b45c8074-8635-4dd1-b699-08d8df185304 X-MS-Exchange-CrossTenant-AuthSource: BN7PR03MB3618.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Mar 2021 14:18:04.0520 (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: XBvCavDtZhRJNwsTgoLgD7sdO2xHraB7MoqOmmePfWzil2JCz2QjAQTF+iu4yuTfWCI8/AZpiHKojE2B94QlJUIko+obF9owsTHe2dhlLWQ= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN6PR03MB3186 X-OriginatorOrg: citrix.com On 04/03/2021 14:02, Andrew Cooper wrote: > On 01/03/2021 19:33, Boris Ostrovsky wrote: >> On 3/1/21 11:23 AM, Roger Pau Monne wrote: >>> Introduce an option to allow selecting the legacy behavior for >>> accesses to MSRs not explicitly handled. Since commit >>> 84e848fd7a162f669 and 322ec7c89f6640e accesses to MSRs not explicitly >>> handled by Xen result in the injection of a #GP to the guest. This is >>> a behavior change since previously a #GP was only injected if >>> accessing the MSR on the real hardware will also trigger a #GP. >>> >>> This seems to be problematic for some guests, so introduce an option >>> to fallback to this legacy behavior. The main difference between what >>> was previously done is that the hardware MSR value is not leaked to >>> the guests on reads. >>> >>> Signed-off-by: Roger Pau Monné >>> --- >>> Cc: Boris Ostrovsky >>> --- >>> Note that this option is not made available to dom0. I'm not sure >>> whether it makes sense to do so, since anyone updating Xen to such >>> newer version will also likely pair it with a newish kernel that >>> doesn't require such workarounds. >>> >>> RFC because there's still some debate as to how we should solve the >>> MSR issue, this is one possible way, but IMO we need to make a >>> decision soon-ish because of the release timeline. >>> >>> Boris, could you please test with Solaris to see if this fixes the >>> issue? >> Yes, it does. Thanks. > Really?  This doesn't stop #GP being raised for RAPL_POWER_LIMIT > AFAICT.  Or am I mistaken about how the bug manifested? Actually never mind.  I've figured out why.  I have another bugfix to submit. ~Andrew