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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=Ia1kB0C85GHc1LlulK+3kx3ilzfPvMweUNMVqRuPZ9w=; b=PS/lYVWY1SneTaChXQuvC0NZNJE8kubIeqC+oc8TCVQgvO4QL22iwb7wctJU60W760czC+YP7mP7XhgbDheIP0JGFYlTiYS2lo0e0UtHfncJ5YdygMINm7T9AJVpTh4BKutrBOP8s/OPQEvw5C3ychBF9AfV2Mz7Rjia0m/myHo= Subject: Re: [PATCH 1/4] x86/PVH: de-duplicate mappings for first Mb of Dom0 memory To: Jan Beulich CC: Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , "xen-devel@lists.xenproject.org" References: <013c49f5-7a14-9d9e-4d25-75934bf6349f@suse.com> <9cfc122f-dc4e-9dc0-0b57-48abf941025a@citrix.com> <866a3677-1f1a-e0e5-7ab0-10c210e25610@suse.com> <2265ca67-2a30-a858-38ba-a6343782929e@suse.com> From: Andrew Cooper Message-ID: <2ef761cf-e609-e0df-e360-9e904f5ad9a2@citrix.com> Date: Tue, 31 Aug 2021 14:27:50 +0100 User-Agent: Mozilla/5.0 (X11; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?U2FKSHFoVytHcTdwdUVHY1VPR1FrQnYvd1hreFBlZFVybEgzNlNuOEVOL0Uy?= =?utf-8?B?c2RVMU1VYnVZUUJJdUpSQXdpd1p4T1ZyT1JNSXh6ci9qclhTYUxzdUQvMEtN?= =?utf-8?B?akN4dG5wdzZTR2kxUzdPVmZHZGV0dWV3RC84eDNtMEVSbHNEdEszZmpsZWFk?= =?utf-8?B?a21JYkVhR3Z5VGRMWXBRdlJlR1h3SWtVQk84ZnR1VFFVeVU0LytzMzBZNFJo?= =?utf-8?B?RUhGZGc4Smx0VjFIVGZJT3VxN01TL0FiR1lQZ0FIL2Y1UlcvcVpwRi9qeFVM?= =?utf-8?B?b0txaklwZzdUbU45cG9uekJVZEhCMHJ2bFluVjFYWm1jZHJ4WlFWUC9HeEt6?= =?utf-8?B?dTV2R0cwcWx1K2dkbk5GdkhNd1NqRjIzd3RpR1dvRVYzZFE2S002UUY2M0Rm?= =?utf-8?B?TElucEFQRHBDUkhHSHdkV2VIWkVkQzFoOHpwYnpRaVFuZ1ZOeVhMWGdXQThM?= =?utf-8?B?WFVnOXR6Q3hwUGdwQlB3SHh3QlQ0QjczcWFVSE1FaVB3ZU5BU21uelFvMVp1?= =?utf-8?B?eDlzdUdzWWU4YWFjcmJibHc1M2RZSlM5Qm8yM0tKamRETlFYQmhCU09YcjYr?= =?utf-8?B?QjR2OGVOZnNZQ0JNRWc4NmtGZHJ1WkN0aFh5aDIvWjVoektvVllUMWFnWlYr?= =?utf-8?B?T1FjRzVkWWRiM0p3OWQ0RURyRFpzRGtFSXNLYnVFTy9OTzg5SlllTEhQOE80?= =?utf-8?B?Z2Y3YmpCSEhoQ01PdzU5RVluTXZYUGlraWdZVTA4YVhPeE91S2drcDdCaUtr?= =?utf-8?B?U2FJRkVWaDVKZno1dFpSRnMydFdSREdZUFhZT0J1dk1SYkZHajlKREhNSmor?= =?utf-8?B?eUNHVFVpUXFOKzVaRGU1LytwMFFPeHArTXVhSnM5SXV2ZGgzelBSYm9OYUNO?= =?utf-8?B?U3RjaU5VcWxaeHZIWitJNGtGcTlJc3ppSUJrUjRxeksyK1JsWUlyaXJNTng2?= =?utf-8?B?YUJWMDlFalZyOXpwWHl6RVBJZmx0Uy9PVjRUaUEzaWxCNjVLVmltUXdPeHJX?= =?utf-8?B?RFlYc2EyT0l4dC9LVjIyWkkrQlAxeWdQMUQ5THZqVUtzNU95RnFzcWRkUnlm?= =?utf-8?B?ZTBka3hZK0hTNlJJNHhqWENtVmlWOVM5eDNYblBHZkROQ1JRUWdyTVB5U1dk?= =?utf-8?B?Q2FuRWE2TnNpSFl1UTFUaXpFVXB2OWdMOThRN2RkY1BzTjFzODZvbFBZT09m?= =?utf-8?B?N09semQxczlDaFhTdmxGb20vVkdYd2NSK1I1UU8xbGNqRWIzQjNRM0hHUUxL?= =?utf-8?B?ZElaYWhsbjNDdnJMQlgyN1pVOXVBeWJMK1cyaG5YSW9YaWgva2xLOEtsTWxx?= =?utf-8?B?S3ZCdXQvUVY0Ym5wc0phOVpuYmd3cDFZZlRDdUo3VGNPOFZnVmswRUFQUy84?= =?utf-8?B?Zis4bytMQ0t3Slh0NU0zTTZXQzkzKzJDeFZ2aEZhN240cVZuTy9kOGwwZ3c1?= =?utf-8?B?MGFXdDd6a2FoT2pybzVNVEszNjk5NjU0enlCWDJoYXBNYlAzZVdZS0cyenZj?= =?utf-8?B?cElweXRPa0t1MWJtaTFkQmUvQjR3VGVmNDFQUzFCVklBM2Y0YVBjRDczajhm?= =?utf-8?B?Y1g1RFk2SE10d3dWVUxpRGtMY3JwZG5XNTdBSEswZUZianlyZnI5YjJhZW9y?= =?utf-8?B?ZURwa2lMZ1dBRGtBc284ZVJ3S3VRUENlMUVscXZJdUtuV0szaG90ekZ1NG1H?= =?utf-8?B?RXM3MWU5cVg1Qk5ZL0xqNUZ1eXVvODBFWFltZ0prUXlHQnpUSTROQlFDRlh1?= =?utf-8?Q?SXdi+9Np1PuEaQBrUSKvmbii8H+m9fQcuTHvCNo?= X-MS-Exchange-CrossTenant-Network-Message-Id: 64fc5d37-e797-405b-6298-08d96c832524 X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB3623.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 31 Aug 2021 13:27:57.0492 (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: /TMBd8KILGdqm9krhMf4hMXU/5vXbrO0Jcmc/5tmZk9ccQhgsFaFTGr6rVc7RGsX+QMeldd3xOucjAwH5YRX4HqqR5JCI6UF7LddfEH9W4c= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR03MB3495 X-OriginatorOrg: citrix.com On 31/08/2021 14:19, Jan Beulich wrote: >>>> @@ -1095,6 +1101,17 @@ static int __init pvh_setup_acpi(struct >>>> nr_pages = PFN_UP((d->arch.e820[i].addr & ~PAGE_MASK) + >>>> d->arch.e820[i].size); >>>> >>>> + /* Memory below 1MB has been dealt with by pvh_populate_p2m(). */ >>>> + if ( pfn < PFN_DOWN(MB(1)) ) >>>> + { >>>> + if ( pfn + nr_pages <= PFN_DOWN(MB(1)) ) >>>> + continue; >>>> + >>>> + /* This shouldn't happen, but is easy to deal with. */ >>> I'm not sure this comment is helpful. >>> >>> Under PVH, there is nothing special about the 1M boundary, and we can >>> reasonably have something else here or crossing the boundary. >> As long as we have this special treatment of the low Mb, the boundary >> is meaningful imo. I'd see the comment go away when the handling in >> general gets streamlined. > I should have added: And as long as Dom0's E820 map gets cloned from > the host's, which will necessarily consider the 1Mb boundary special. Not when you're booting virtualised in the first place. ~Andrew