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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?Yk54RTVvSitlODJDREZUTnNRb2JMWDg5dFVoQmJXTUZXK1MxSHkzMWJycThP?= =?utf-8?B?UDBGVnkvRDhkWStMNlNlUjZSTitpM05nTG5KaXQ0S0IwZ1R2TjcxbGtYSGFm?= =?utf-8?B?bUxiSXBpVHZUejMrdUc0WEUzMk54NDZCbzV3YVllREZQUEp2L1dPNXZ0ZCtD?= =?utf-8?B?aDlTTW5qcSs1SFNnNk9mOURKRzVPZkJ6M3gzUGxkTkpqUVJmS2FWRnJXTitR?= =?utf-8?B?WS9IcHc5MCsvc2NBdWdqbC9pQ3d2QUQ3OEdHWXdpczNpNlVscjNIVUx3bDNW?= =?utf-8?B?cFJ5Q1I3QUxLZmpzV3JhZXI3WXR4N3RQQTJ4VDg4VUlVZE8yQ20zRk9DVjFI?= =?utf-8?B?SkczVXIwNThzSHFuVitlMng4ZlF2WnppNXQ5NDJNU1Z4NW51eU80MlNKejZw?= =?utf-8?B?RlNxTkFkKzI5ODI1dk5JTGVIOEFLYlZKSEJua1Z0Y2VGbEdZdzhGRnBISFRG?= =?utf-8?B?T0w4cEJKbWJXaVJRQzZZWTZxbGgxK0Z0WXpxMnNOMmNTeUZINDM3K09kc1dX?= =?utf-8?B?UnZXZWdGbVNmaysvK0VXUDlyOHhYU1dodU9pWkJKRWxsekEvTkZqNTJEN3hQ?= =?utf-8?B?ZnJsNzRhclFtRk1QdzRTbmkyYllrL3ljeVF3T1JpRFNydkVXNFpIZVVFWFNx?= =?utf-8?B?clJ6Z2xmdUZxNEpYTjZ4T29WaDVRb0tCSG04clh1TFVac1prWmlCbGtOWTZG?= =?utf-8?B?dndaNmhzeHRuKzVpdmt4WmVnZExKMUNZN1ZXUEtZaFp4ZHNQOXlDOGpKWUNr?= =?utf-8?B?elJuck9tdktsT2JaWktUeVpTaVBqdmt2eGpYWEd4QVU2NHNJazFNeERHQkkv?= =?utf-8?B?bkdRR1RKak5aZFJYWXVBZDBOemdTcnAyZEQrMTdLTlEraCtEYzFmQ2FXV2FU?= =?utf-8?B?OU9hMldSWERkNDNGTWg5czlLZG9XSjBPR3RiM2FWT3RLUU5yUENnMjVpaXR0?= =?utf-8?B?SSt4YUpMMGhycWFRQUNLWSthVFhObjYyQWN4VitQOWFzZ05KTk1HNjlxRlFC?= =?utf-8?B?UWJ5NytOZ1dHdmRpaW41Vko1MHhXczBJbThNTXpzRDE1NG9VL3BOQWV1K3hL?= =?utf-8?B?bzBqbWpvSit5T2h3SjBKN1NSaTlZTkVNR1BFOCtpWHgzcGxJNFFCUHVFQ1lh?= =?utf-8?B?RHEzMi91UU9RM1hiVGFGZzI5cUtSQ3luTzlMekxGVTNFTkVFUjNTcm5WR0dY?= =?utf-8?B?Q0NqRTYvYW01QlUza0FSN0FNSjIxMHkzOVJFeFZ0RWd5aGNmL2xlcTN3dWlD?= =?utf-8?B?OGRTcllhc05WdnpkOWYyOFBlcU8vL2M2R2Y2cUpHVzRoZlFlRlBnM29zcEpJ?= =?utf-8?B?UjE2bVNtM1V2cUVxVzR4RTU3Q3VEc2lIN1pubXVqbGFDdWwwVVFiS09LY3ZB?= =?utf-8?B?bS9INTEyM3AxaENiNnFQNm9rNmZLRUREY0d2a1VIWW9pcnREOXJBamRoc21j?= =?utf-8?B?RWF1cjRBdzlMTXV0MGREbmlHb3hFTHdOcDh0S2pIbXBwLzcrT09OaDRjTk9K?= =?utf-8?B?dElnZWpXSW1kQVlqRkFHbmdRSzcvTTh5c05WOHc0U1VmeWlFa0d3SmZYakoz?= =?utf-8?B?UE5Ja280emxLV3dhZ1FxbklBanhSbTdjMDZoU0czUzZFdy9VMmhBOFdEVVhI?= =?utf-8?B?MWpXc25XZ2xnWk9GYVM0eWJRYUxhSnA4Q0EvaldNYVZjclRxbWRJRHVuNWVD?= =?utf-8?B?am1UQUtadGJxOXg3cTdFZW9FdlNCN3FXQ2lacnNsZXIxV0pLKy95THh1Y1Nx?= =?utf-8?Q?preCFCU3zJ34NqLVlSsYy/cqCMbOemgHg7N0Xbj?= X-MS-Exchange-CrossTenant-Network-Message-Id: 743f8c3d-d546-4a85-e40b-08d8e22ddfe8 X-MS-Exchange-CrossTenant-AuthSource: DS7PR03MB5608.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Mar 2021 12:29:53.2824 (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: XcHTaJ2T00KyaMFwERWFNs5ePFJM1NpIFXbPXfCBxEBT1LprBz/EzY4CiL4H9ArYHF3Ls1vewWxJnb5qXdhWWw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR03MB3673 X-OriginatorOrg: citrix.com On Mon, Mar 08, 2021 at 12:47:44PM +0100, Jan Beulich wrote: > On 08.03.2021 12:37, Roger Pau Monné wrote: > > On Fri, Mar 05, 2021 at 10:50:54AM +0100, Jan Beulich wrote: > >> Linux has been warning ("firmware bug") about this bit being clear for a > >> long time. While writable in older hardware it has been readonly on more > >> than just most recent hardware. For simplicitly report it always set (if > >> anything we may want to log the issue ourselves if it turns out to be > >> clear on older hardware). > >> > >> Signed-off-by: Jan Beulich > > > > Reviewed-by: Roger Pau Monné > > Thanks. > > > One question below. > > > >> --- > >> v2: New. > >> --- > >> There are likely more bits worthwhile to expose, but for about every one > >> of them there would be the risk of a lengthy discussion, as there are > >> clear downsides to exposing such information, the more that it would be > >> tbd whether the hardware values should be surfaced, and if so what > >> should happen when the guest gets migrated. > >> > >> The main risk with making the read not fault here is that guests might > >> imply they can also write this MSR then. > >> > >> --- a/xen/arch/x86/msr.c > >> +++ b/xen/arch/x86/msr.c > >> @@ -315,6 +315,12 @@ int guest_rdmsr(struct vcpu *v, uint32_t > >> *val = msrs->tsc_aux; > >> break; > >> > >> + case MSR_K8_HWCR: > >> + if ( !(cp->x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON)) ) > >> + goto gp_fault; > >> + *val = K8_HWCR_TSC_FREQ_SEL; > > > > I've been only able to find information about this MSR up to family > > 10h, but I think in theory Xen might also run on family 0Fh, do you > > know if the MSR is present there, and the bit has the same meaning? > > From its name (and its K7 alternative name) it's clear the register > had been there at that point. And indeed the bit has a different > meaning there (its the bottom bit of a 6-bit START_FID field if the > BKDG I'm looking at can be trusted. OK, I cannot seem to find the BKDG for family 0Fh. The oldest BKDG I can find is for Family 10h [0]. > Since I don't think it matters > much whether we expose a value of 0x00 or a value of 0x01 there, > and since we likely don't want to make #GP raising dependent upon > family when we don't _really_ need to, I would want to propose that > the value used is good enough uniformly. I would be fine with setting it to 0 if Fam < 10h if you think that's acceptable. I think the chances of someone running Xen >= 4.15 on such old hardware are quite dim. Thanks, Roger. [0] https://developer.amd.com/resources/developer-guides-manuals/