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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?dlpvd3FaNHIxTHgyMVlqYTlEamc5OTZaWXNEL1IvenpLdjhzVEtIUldyZjVU?= =?utf-8?B?T2lRemF6UWx5cUtGclg1dlBSQWMxNUtENUZvcFBGNDM2ZGJmWnIrL3BuQmM2?= =?utf-8?B?UlVpV2s1VWpQV3NBc29Cc0VUWnZacTFUTDJnUktZWm52SlFKZjJ6d2dFbnhs?= =?utf-8?B?b2xiNVVtYUNpUm1GT1IwREFUMW9TWUFCczU2eHBDTW93ZW5laHgvM3N0RU1K?= =?utf-8?B?cmxZL09PZGladlJ1R1JBQUQ1MC9PcHlpcTBudlVZRHBLOTFzTDB4aWZkRmlB?= =?utf-8?B?K0pWOTFBc0t0TjFmOTg2cWxEcHV1Si8rT0NobWgwSlR5bTBCNkY4ak5SMmwr?= =?utf-8?B?OVpIRTFDRmh3NFVlRkVZUXBFbXp0VWJtMkNlZWxaUkZORDBMZzlwYVl6SVRL?= =?utf-8?B?QTV2WlJ6T2pXSEs5Q1NCZDArQzZLQ2JESzdUMmxkbGt3aGJyWk5MNW1zRkFS?= =?utf-8?B?YS91MnFXZnVoMTluL1h2MmgvR3YzRnQvS0RGWHh4ZTVUbHRMMzkyVDY2QzRp?= =?utf-8?B?RjRDeEJRejBVaEd0ak1tMkk1TFA3a0h0eEZuSHRlT2FkTlc4TnNod25oMmZN?= =?utf-8?B?YlVSZ3Y0QStYcnRueU5QbHBoYzFVSTlLakpBL2V6VUpXSm1UQTFQN0o1UDk2?= =?utf-8?B?VE5OUTdzekpYQ1M4Ym9XUE93UzJ3NEhBMTRVOHFRdFVwYlpFTm1HYlhGUzEy?= =?utf-8?B?QmppU0V6dTVPL1E4QTU3b0M0ZkdUQTl1RzZXRGtDWm9WSGtvZkdvWDNJNGVy?= =?utf-8?B?b1lyTnJUbVdrTzVDS0JudXBUNVl4TDcyY2xFK2tDK3ZDVVlKWlZ1UTEvWmZB?= =?utf-8?B?SzQ4a2IzQUwvWUZCV1Z1ZXJTNjFLaFhld0QrWkdSd3dlUXdTQ3JKYXV2Y2xO?= =?utf-8?B?Zk5xdTYrRUFCOWQ0U296OGRlK1ZoRGRteVJPNEpjZjNnK01IcmY1TVdlZkxm?= =?utf-8?B?Uy8zV0VScDRFcCsvcnhoR21rZnBKelFqT2hDYThMK3BVaDMzbUNNSVJDZXhV?= =?utf-8?B?OXAxODBFZG5NelRvOGlaUzZ6a1JnRklvUGJpZm52T2NZSThKaXFVMVZXQ0dM?= =?utf-8?B?bGlEdmdZa1JoMjU0WG8zd0FtanhBRWcwbUs1Q2xxNG16WE1ESlRQU3NYRENi?= =?utf-8?B?aUZzMnlWNkI5Q3pZNytlN3A3MnA3bTFvYW11cWk1K3NibHJXZFBHM3p5MVd5?= =?utf-8?B?UUlVd0tGbUd2TU4zNDN3R3hVc0I0YmUyd1RKNElQOU5tUlhwcW9TcE52bzB3?= =?utf-8?B?SkRjMm9KdmNkU0E1T1ZON0pKckVnSjRuREYyVXN3SHRVUUlpSlNJbmdtbnFj?= =?utf-8?B?WU84UVNsQXEvWVBtOGtvVkVFV0xXWTl6MVlzRHpnd2owSEVkajVMdW5SUWtr?= =?utf-8?B?NzNOeXFZdE82TGN3QUl2K0Ixa2pIQ1ArQzNhc1BCbCsxVlk5eDhWOVg4YlFO?= =?utf-8?B?UU1tWFhvZzlsWjRReGFKMmpsMlVNWDdWcEFFUjZMK2VtZDVXYmd4VC9hUlZC?= =?utf-8?B?S3hnNXJvMEZneVpTejBlcytTSysxUmFTL3E3Vm96UWZkbDZZTGdiNENZVHFy?= =?utf-8?B?NjFhT1FPMjIybmtoRFV1VjRMN01PVGFFNlNzdHlLWE9POXRlZWs4VE43Ny82?= =?utf-8?B?SmJEdEdWN00xYTZzbFlKbzRwdERkRmNTaE0zc3F1RHo3bGVNSklTOFVZeFBY?= =?utf-8?B?bVIrazYvQlhWZkFVNTRhb3JvSHdPUjNCeitETFNzeU9sbk96ZkF5SXBSNkow?= =?utf-8?Q?3B/nDFgJ6nPDp9guKR4vp/y8aW4PmbJHSms7uq6?= X-MS-Exchange-CrossTenant-Network-Message-Id: 98196949-8a03-4eae-6d11-08d8fe65856c X-MS-Exchange-CrossTenant-AuthSource: DS7PR03MB5608.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Apr 2021 10:18:45.8519 (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: 3PGnbXq+yH5oTQgxpdncpXQMFT0MXVaUpYXtbGehmaCCgFeufGFDO2DM8srjyuXbb3VzikGEBeSa0+Fn8aCdew== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM5PR03MB2556 X-OriginatorOrg: citrix.com On Tue, Apr 13, 2021 at 11:24:09AM +0200, Jan Beulich wrote: > On 12.04.2021 17:31, Roger Pau Monné wrote: > > On Mon, Apr 12, 2021 at 12:40:48PM +0200, Jan Beulich wrote: > >> The address of this page is used by the CPU only to recognize when to > >> access the virtual APIC page instead. No accesses would ever go to this > >> page. It only needs to be present in the (CPU) page tables so that > >> address translation will produce its address as result for respective > >> accesses. > >> > >> By making this page global, we also eliminate the need to refcount it, > >> or to assign it to any domain in the first place. > >> > >> Signed-off-by: Jan Beulich > >> Reviewed-by: Kevin Tian > >> --- > >> v4: Set PGC_extra on the page. Make shadow mode work. > >> v3: Split p2m insertion change to a separate patch. > >> v2: Avoid insertion when !has_vlapic(). Split off change to > >> p2m_get_iommu_flags(). > >> --- > >> I did further consider not allocating any real page at all, but just > >> using the address of some unpopulated space (which would require > >> announcing this page as reserved to Dom0, so it wouldn't put any PCI > >> MMIO BARs there). But I thought this would be too controversial, because > >> of the possible risks associated with this. > > > > Really seems more trouble than reward. Also there are systems with > > MMIO regions in holes on the memory map, like the issue I had with the > > Intel pinctrl stuff that had an MMIO region in a hole on the memory > > map [0], so I'm not sure Xen would be in a position to select a > > suitable unpopulated page anyway. > > > > [0] https://lore.kernel.org/xen-devel/YFx80wYt%2FKcHanC7@smile.fi.intel.com/ > > Yeah, I had seen that. What I'm having trouble to understand is how the > OS will know to avoid that range for e.g. placing BARs. No idea really, I assume they expect that you parse all possible ACPI devices from the dynamic tables before deciding on any BAR placements? I still consider a bug that the pinctrl MMIO region is not marked as reserved in the memory map. > >> + { > >> + const struct page_info *pg = mfn_to_page(mfn); > >> + > >> + if ( !page_get_owner(pg) && (pg->count_info & PGC_extra) ) > >> + { > >> + ASSERT(type == p2m_mmio_direct); > >> + return 0; > > > > Are there any other pages that could pass this check? I don't think > > so, but wanted to assert. > > "Normal" extra pages have an owner, so no, there aren't any others. > If and when any appear, this may need further customizing, albeit > generally I'd hope further pages matching this pattern would also > want similar treatment. I wonder whether we want to add an assert here to make sure only the APIC access page receives this special handling by the shadow code, but maybe that's a bit too much? Thanks, Roger.