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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=ZmcK9Y4uFBjkYUXcotUtMKLlgljfb7Qzt6kbazAoOsk=; b=RMayFyUtWHoO4EkfVTm2gIzorjWatpulWVMlBF0WhLU2nTdK0PfZsTdvmrbm37YLlDLbPmJHIWSC1XVoLrDE2UYNzpo+I+Z5amYgmRMH7dh3ZDpFxUuqgECDxZhxngu4X3WAJmspPitAGLmCjnXMzTb9XFFB1Z1KXpAIF6RASbY= Subject: Re: [PATCH] common: don't require use of DOMID_SELF To: Jan Beulich , Julien Grall CC: George Dunlap , Ian Jackson , Stefano Stabellini , Wei Liu , "xen-devel@lists.xenproject.org" References: <72c9f0ec-81e3-63f9-2513-46e463642219@suse.com> <6b80d9bd-58a1-0854-2ff9-7153ddecae26@xen.org> From: Andrew Cooper Message-ID: <96130e56-9054-3e7e-fa83-e8d9be6b7323@citrix.com> Date: Thu, 14 Jan 2021 15:36:36 +0000 User-Agent: Mozilla/5.0 (X11; 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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?alZTZm5kREIxSmZ4eU02a0l4MERHZldXUW1zb2cyRFU1MkloN2lsQUlxUTdx?= =?utf-8?B?WTF2RjI0TmE2MXlubUlCMVUzUkdZTExrVnYzQ05JTnJrNCtSVjQ0Zjl2Q0Vh?= =?utf-8?B?TXNZdUZ1ZjBGYitVaVNwb1lKeGUwcE00ZlhpYVZ1SVB6Q0t3U2lvc0NMQmJT?= =?utf-8?B?VFJWZHFKQVE1SkRsZFZSR2hUa3JXZWxZcWlGWUlIZldXSmtRTWlyUGZlclVS?= =?utf-8?B?TGlvZFZxMCszT0JlL0tZMktmVGc2ZFRqUUJGcHdON002MFJSV1lRdUtKdGM4?= =?utf-8?B?aUp6MnlkOTZBY1NiZzhBTThtM3hNU1VNbW8rK1ZLZEhIeks4VlFrVVFMSnlo?= =?utf-8?B?aUxJenpIdW5Ga0xneFIySWhQQkllcWpVTE9kaTVtbTRCK20rZS9UUmxnVnRu?= =?utf-8?B?WkdadzJkanh2MEVYTHdmUUx3MWpQQ1N3OFlld0lucWZxdlJCakpVQXhiUm1Q?= =?utf-8?B?SysrektubG9RVXhwVEVwTEhRYzVLcVRGdmZ0R2tnSjZpS2RsajdDWTg4VFU0?= =?utf-8?B?YUtyc2lzWjlJNjJOTGhtdTZLMHJrM1JGTzFuZ01yYStkK29LdGRGVE5rT2I0?= =?utf-8?B?QWhaQWx3dEljZUhZQVA5MHlWbTVwZ0lTZ1Irc05MUzhMalRMZUlIdEkrOWc5?= =?utf-8?B?S1lnSHFZcW1lZVhBZ0pFM3ZxRUowQWdqYTRGNGdPL3pxWTVXV2lmTk11VEI4?= =?utf-8?B?UkpxN1dqM2dOdWU4eEEvWjR4VlRBOGo0L3lyU1EyMjdUcHNBYVpkd3pLRHdj?= =?utf-8?B?K2pkeWluOUlpUGllSEJxSWRrWktUMjRUZkUrM1JPa1VSQlhIeW43NjRLU0lo?= =?utf-8?B?djErcVJXZTgvWGJOOUh5aWRGQ2trTjJtdkpOdXI1ZWlYSFROVzRBRU1Qbkw4?= =?utf-8?B?VHprTkIydXd6ZGNWMXl4MWlxVXBmdWdpWU9zR0x3TU1iYk1GelNvSTNia2FO?= =?utf-8?B?L3paajFVOFE3dXRhazJnMkNjT3BVZUtXRjR1UVUwd0cvVnp5YkpoZWhXRks1?= =?utf-8?B?ZkZEckFsamowbnhkVGhGbUx3UUlpV3hIVE8xM0tvUHJGbjRDbTZhTWVXWTQz?= =?utf-8?B?b2ZKRXIyQWtBSjlIZHQ2bkYxN0grQXRqbnJRK01FckhsRzdqSk1HdFZOdFd1?= =?utf-8?B?Uk9GWnE3dU1qNVJRb3ZOZ3R2RzNjYWxoQW5HZk1wTmtISmRJYzY5Tm9LYjJS?= =?utf-8?B?bG5ySGdSNmhzd0V4dDd3NmU1Vk41a0kwN09vZzBvTHBDeEJod1Bicnk2amJn?= =?utf-8?B?SXAva0JQQ3lRdjM0TkF5RHhtUE4zdi8ybmlzWkd0bWZOSFJQaDQwckxBNzBG?= =?utf-8?Q?S2kqoyR1bPBO1TjI6gG0uOeGj603sk3tzO?= X-MS-Exchange-CrossTenant-AuthSource: BYAPR03MB4728.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Jan 2021 15:36:42.5996 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 335836de-42ef-43a2-b145-348c2ee9ca5b X-MS-Exchange-CrossTenant-Network-Message-Id: 5fb5d101-2ef4-4a3e-759b-08d8b8a23178 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: /RGHGOz0IlX1G29AbWihpKGx0xm3f2u3ksaK11Kr8gMLjwgtQixf2CG77q2LoBmW8cv/9kLxRRvQ+Oha1gQ9XEOxD8BxNO1vPvkXz71fOVY= X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR03MB4773 X-OriginatorOrg: citrix.com On 14/01/2021 15:30, Jan Beulich wrote: > On 14.01.2021 15:43, Julien Grall wrote: >> On 14/01/2021 14:02, Jan Beulich wrote: >>> It's not overly difficult for a domain to figure out its ID, so >>> requiring the use of DOMID_SELF in a very limited set of places isn't >>> really helpful towards keeping the ID opaque to the guest. >> So I agree that a domid can be figured out really easily today and in >> principle it would be fine to relax it. >> >> However, most of the guest OSes will care about running on older Xen >> versions. Therefore they are not going to be able to use this relaxation. >> >> So I am not entirely convinced the relaxation is actually worth it for >> existing hypercalls. > I'm aware of the concern (Andrew has voiced it both here and in > earlier contexts), but personally I think undue restrictions should > not be retained just because they used to be enforced. We've gone > this same route in a few other occasions not overly long ago, and > iirc there are two patches going in a similar direction (different > area of course) that I have still pending and which neither got > ack-ed nor firmly rejected. > >> Anyway, if we decide to relax it, then I think we should update the >> public headers because an OS using this relaxation will not work on >> older Xen. A developper will not be able to know that without looking at >> the implementation. > Well, DOMID_SELF exists because that's the preferred form to use. > I can certainly add commentary, but it would feel a little odd to > do so. To be honest I'm also not sure how helpful this is going to > be, considering that consumers often have their own clones of our > headers. What I envisioned would be an RST ::warning in the "how to grant table" guide for guest kernel developers in the sphinx docs. Of course, this presupposed that such a doc exists, but its the only useful place to put a note. ~Andrew