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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?T3Y1TlBhYVpBdlozU2NqYyt1WjZhZmxMOVpIRzg5cjJ4TFhMelBvaS9lZ0Vm?= =?utf-8?B?ZmdsdkR4VkFXTWNySUNzclRRRFhQSFpDT1NhR01vSm8wNXAxcEo2dC9jS0Rn?= =?utf-8?B?R3VjMDJMQkg3bURXY0ZMemJ2eS9TN2JqZXp5Z2I5WHNZUnJqbUVlS0ZodjZ5?= =?utf-8?B?NnhBTGtsWDhtakhzRFQ0d2NuK1NnN1Vla3EzQkprTWlvdHVHL3NSR1Z4OXY4?= =?utf-8?B?ZFRxTnVMYWY5bkVmZEtYMzVIU2lkWDJ2WWJCNkoxNEFzR1hQKytZbnBoVHZN?= =?utf-8?B?OGgxVElzaDA1NEsxOXlvYTgyM1NmUVIrTG00OEZ6OE94OUwzTEFmeHU1aDND?= =?utf-8?B?cFpyUG02OGZlRW9yamcyRGhlU0wvL0Z2SVY4NEkwZFBjRWFBMWNDYU0vd2d1?= =?utf-8?B?bGFMNkJKSUR0RGNIV1JlM3REVnYxN3dLZnRlUExWZHFlWS9sTkZodWJLU2Jx?= =?utf-8?B?L0h3cWN2aFNXSXQwbnhoYWQ5L3g0bXN3cnczV0xFMUZVUWZLUjRZdmp2SnFH?= =?utf-8?B?YWtDLzNwRklkZDZ2NEQrd3lCRm5TY0k1UUdCQk55OVNSK0J6b1k2em5PWk52?= =?utf-8?B?MWNLcXFsU2ZGVVFHTmovK1U0MHgra21NTnJBYWwrTzJlNmN2RjIzeVBzc2Uw?= =?utf-8?B?bFFhNHlVb1VzV1phbm9UdUdMWCtEWURmUGdFT284R0pENXpiYUUyOGlLL0p2?= =?utf-8?B?dmtQWE8rMDQyMVFUK3M1Z1MrOFpqQjY2dk5OM01yRnV4Njh1ckpWSEJNak8r?= =?utf-8?B?aFpUdFpmQlhpM0paVWlOY3h0aWlMamtyaW91QWlzRVRGa0FTODRVcldoR0F0?= =?utf-8?B?eTJpQVFBcWxQTTQrZlkra3JXSmlTMmozT1NiZStzR3l3WlNBK01ZdTJCY1Ry?= =?utf-8?B?VG5OMUFOZVI2VUxIUlJJRFFrdVBmTDhQNlNFZkhvQmpTdCt3SitkYVdORkNG?= =?utf-8?B?cFFRMGZGMEtQRGV3eGUxUUdUWERodGpIYTU4WXd1YjdoL0lJL1NhZ2g0M0wx?= =?utf-8?B?bTNLcEZxRHZ4WW1RbFZEUFhyemtNdkhYUmxpREgvTmlpalB4eERkZi9NYTAz?= =?utf-8?B?YWlXMWVpRDFkT1ZSSVJvdjQ3a21IVW9RM0cvTDFoKzVMM3U5QXl3K2pGMUZI?= =?utf-8?B?cmkwektsSlM3V3JhYmkrR2VVZmI2RGVLZGlmRkJDQ1dMVjF1YmhLNklibjhK?= =?utf-8?B?NEcybTFQSFlHc1U1bDJ4THYyZDFBY0JJaTFydG83UXhtZEFoYllNakJhNGlz?= =?utf-8?B?UUxqU0RVeEpjYzJ0MS9sTUl0T0J4NVFicEJ2NlZlOEZhdXcvVFdYR3hLdm16?= =?utf-8?B?Zm9EMit4ZVp1RkZGdWlycU4zYkR5SmtVdGFDMEk1NFl0WEZ5ZnlyZ21EaHRi?= =?utf-8?B?citkam51TFpHNlVGWU5FbmI1NklyVys4cFhDamRCcElNRWNwc3VmWWF1UWdW?= =?utf-8?B?S0lJc2ExeU1OdVUwWThkRTNXOU84NEgwYi9nRjZZKzduUEw1eS85ZVVHNTRO?= =?utf-8?B?dFdSejZlaXcrOFlGd01jSnJ5cU9Lb0ZEZWRvQjN6RmlvZWNqczN2NkxkZS91?= =?utf-8?B?N1RqY0hvRkc0a01vd01VMXNkWkdLN0ZKMGVVbFkvZ3pFQ2NGTFpHU25LTWpl?= =?utf-8?B?ME5vd21QWDM0NXlISXB2bVpmRXloWk5sR2x4bXVhN3MxZGRJOWVTMWFBcHJz?= =?utf-8?B?OThnelB0SHd3UCtLNW1nOTIzUHFBU3lIZ1drajQ2ayszNkRYeW5qYkdJSWlj?= =?utf-8?Q?fErSOpDSHPG/ipHTr1rwSr5EVi9yHQOvAHJOAe7?= X-MS-Exchange-CrossTenant-Network-Message-Id: 11486de7-d4fe-4f98-613b-08d9359aa94a X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB3623.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Jun 2021 16:27:43.2924 (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: xEDSQL3WkLjScBg3YM6j6qW1thQgLA7c0jtTLMnGaFxbMZ6XC3o2YEYGrSs5AGNIxuS9Fv4g5RruzLJE+SYkfVAEwnz4r84x0JL+0x9iS08= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY5PR03MB5047 X-OriginatorOrg: citrix.com On 22/06/2021 17:10, Jan Beulich wrote: > On 22.06.2021 17:39, Andrew Cooper wrote: >> This reverts commit aad7b5c11d51d57659978e04702ac970906894e8. >> >> The change from OvmfX64 to OvmfXen causes a change in behaviour, whereby >> OvmfXen maps its shared info page at the top of address space. When try= ing to >> migrate such a domain, XENMEM_maximum_gpfn returns a very large value. = This >> has uncovered multiple issues: >> >> 1) The userspace hypercall wrappers truncate all return values to int o= n >> Linux and Solaris. This needs fixing in Xen. >> 2) 32bit toolstacks can't migrate any domain with RAM above the 2^40 ma= rk, >> because of virtual address constraints. This needs fixing in OVMF. > And I suspect even that presently enforce boundary of 2^40 is actually > too high, and things still wouldn't work when getting close. At the > very least the tool stack then depends on a fairly big chunk of memory > (2^30 bytes) to be available in one single, virtually contiguous piece. > Iirc 32-bit Linux can be configured to not even leave this much space > for user mode. I tested it once during Migration v2 development, and it worked for me, but I do expect that that is as much testing as it has had since... A 3G/1G split is the default under multiple 32bit kernels, and the allocation is made right at the start, so there is a reasonable chance of finding space.=C2=A0 After all, it only needs 4k alignment. Whether ASLR has changed the chances in the meantime remains to be seen, but honestly - 32bit toolstacks on x86 really don't exist in production any more, and Arm still hasn't implemented logdirty support, so the limit has little practical consequence. ~Andrew