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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?TG95cUZpQWhONVVIODhvakxlMmFla3IrZTBxTzM1VWFhU0w4VnBMRitiZXcr?= =?utf-8?B?MVk0Y2R6S1pZSXJBOWVRL2EwMEpHbHNFT3p3Qm1JR1B5QnRTbTdVby9mZ1g1?= =?utf-8?B?T2dUTXR1WE9hSk5ndjQzcVFhOXlaNTJJUXQ1U01IQ0E4TThBczhobGh6SzFH?= =?utf-8?B?eDJhZERJcVFZeERTOWRORCttSmxEcTVVVzgrbm1SUCtWdFFMS3hkMTllM2x6?= =?utf-8?B?UTV1RXIzakR0V2prd1ZqUFhJcktnTkp2NTNGOTM2a2YxOFVtTGFuUC8rSGhr?= =?utf-8?B?SjA3TG56MndwVVY4WU1jSUduZUFLRHE4MEZUMkpxTXZLcHV5MlNjeUJlVjNs?= =?utf-8?B?TlB4MElVQnRrQ1YxdFdkUTBqbi9XeWNBZlRDS0k3T084c0x4UXhLWUhMR2d2?= =?utf-8?B?N29OUDVFa2d4VDRLRHI3akc5TllOMnlwS1ZZWjltNTlrZ3JoWDZ1VXhycVhL?= =?utf-8?B?V3NUT1BXOGpWanNLdGdJNE1LUTg3UG44MWV2TXBndWRNaURyR3FnSzlzSFho?= =?utf-8?B?bWlSNDZURkVBcVhvNjhtYU4vMTBiSGF5VDY4SVBUY2ZPekxwMzRuWVJnTEJL?= =?utf-8?B?MUo2ZTR5amNNeUVJMFJhTXdDMXZ1cXNTN0RhVkpaMmh4M29aRG1Wb2F3Vm1P?= =?utf-8?B?RnJ2V3BwSkxoNmdkSlhLSlhjQzRZS1lJb1doREJmVHhCY2EyZDY4MG9qM0cr?= =?utf-8?B?Z0szUk9RR2lBenhMV2JOb3h3TXduRkVMek5oVkM1WnVsdkNVKzM2eE1jbzNk?= =?utf-8?B?czAxK05mVWZYSGltcis0cVRobmNScGhpa2MxelZPSW0yeitneTJaWmJ4TFlQ?= =?utf-8?B?ZzJPb2VzL2hMSFhvQytHMWtiZVgzZlovaTR1ZVFnS0UyUHhQWVVNRVVzKzlP?= =?utf-8?B?RCt5Sm5kVkF4OUVqRjNZd3dZYTBJSHVseFhJdk9jb3l5c014WUQ4TU11YjNK?= =?utf-8?B?RTlGU2J5WTEwam5RQXQxQ3VsU1RvWHlPSWV0cWVRMWo3eWtCbCtPQjNzM2tv?= =?utf-8?B?ZjlzQXY4NmxVQ0c1UFRYTWVPallBYld0NU5xVTRwWm9DUU5NRXZEOGk4ZlZv?= =?utf-8?B?MXhmTmRlMlZGSmh1T0ZiRmdlVXk2S09SSnNnSHgrNGFlQXRLd3lTN3NQbkEy?= =?utf-8?B?SkkybmFJakJMV3RDRlRUdGRBQmxtejNjWnFVQjhOL2FZdFEzN20wazdnNHJ3?= =?utf-8?B?b0l6M2pldm5RSlArc1k1ZmpWeWtGSFN6VXE4NGhHKzFLUCtUMnMxSUpkT3A3?= =?utf-8?B?RWorWEdYVXdVVXpOU0c3OXRna2FPNXpEeGNEUHBYNHIyRzU4QkRSZDlieE0w?= =?utf-8?B?YldUZ2tSWnFYc0RTQS9vUUFBUVNDcjVOaXhXbnM0SU5lRmx3ZDh2TVRNNXFh?= =?utf-8?B?NEFPcHdEYUNzd2VhWVBBZW9Mb0RHcXVXZWtZR3RORVYxdmNZL09ieklUQ1Fy?= =?utf-8?B?QzBXcWJqTkNaOFlHT0xVZzZoVE81Nlh0UlVPd1BhUS9VNEpkcDBHczVpUUVx?= =?utf-8?B?M2cwS3EyVHVCTS82TG5pWU1uOFp5eGU0QTJUdEtlZUp3UjYxUUhiQy9uVWNx?= =?utf-8?B?M1FsMUs3dnVRdENoTDhSRURNcmdvZzNLaTgwdUFNM2JqUUMxUHhxWVJ6dUtG?= =?utf-8?B?eXNibVhMQ3hBSTh4WVpkbElwaTlIazVRTXlGa0JLclBQWG8rM1Y4c1Y5MXAx?= =?utf-8?B?ODQzZ0d4OW1ETDNoekowTDBQam1SbmpNbUNVc2ZjSEJjYTUyWW5TRjZZR00z?= =?utf-8?Q?Hmu+vC6LcvOh4RwEbGhKr6Ei92yqOmpzzK/Ztkk?= X-MS-Exchange-CrossTenant-Network-Message-Id: 064d84b0-459f-4ee2-685f-08d97825193e X-MS-Exchange-CrossTenant-AuthSource: DS7PR03MB5608.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Sep 2021 08:44:58.4280 (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: vGHoWiff+HrpNl5xY06bqkMFkoEuOOTKp+BD1lvQbBKmtahyUlJkSybW/s96Swa9ydFudKuC7SZHTliZqPp1Aw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR03MB3947 X-OriginatorOrg: citrix.com On Wed, Sep 15, 2021 at 10:16:41AM +0200, Jan Beulich wrote: > On 15.09.2021 10:03, Roger Pau Monne wrote: > > If the new gfn matches the previous one (ie: gpfn == old_gpfn) > > xenmem_add_to_physmap_one will issue a duplicated call to > > guest_physmap_remove_page with the same guest frame number, because > > the get_gpfn_from_mfn call has been moved by commit f8582da041 to be > > performed before the original page is removed. This leads to the > > second guest_physmap_remove_page failing, which was not the case > > before commit f8582da041. > > > > Add a shortcut to skip modifying the p2m if the mapping is already as > > requested. > > I've meanwhile had further thoughts here - not sure in how far they > affect what to do (including whether to go back to v1, with the > description's 1st paragraph adjusted as per above): > > > --- a/xen/arch/x86/mm/p2m.c > > +++ b/xen/arch/x86/mm/p2m.c > > @@ -2799,6 +2799,13 @@ int xenmem_add_to_physmap_one( > > goto put_all; > > } > > > > + if ( gfn_eq(_gfn(old_gpfn), gpfn) ) > > + { > > + /* Nothing to do, mapping is already as requested. */ > > + ASSERT(mfn_eq(prev_mfn, mfn)); > > + goto put_all; > > + } > > The mapping may not be "already as requested" because of p2m type or > p2m access. Thoughts? (At the very least the new check would likely > want to move after the p2m_mmio_direct one.) Is the type really relevant for the caller? If the mapping is already setup as requested, I don't think it makes sense to return -EPERM if the type is mmio. I'm also unsure whether we can get into that state in the first place. I'm unsure regarding the access, I would say changing the access type should be done by other means rather that replying on xenmem_add_to_physmap. v1 was indeed more similar to the previous behavior IMO, so it's likely a safer approach. Thanks, Roger.