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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?dExSSlQ3L0FpZDFGZDEybW1YQkxWZ0kwYWx1R05iSkI2djJ5aFF3RkxQQTkw?= =?utf-8?B?aFFOT0gvM0t1VTlBVXFCNW9WYzBUU0RxQUViU3lCbGRVSys3WHNjcERJdm82?= =?utf-8?B?ZzVMa2djY2xoUnBJOTVvRXVvb012WEp0RDV2bEdKZTk4YlNYdm1iUFNTc282?= =?utf-8?B?SW9jNU9FNXpqZ3BkZ3VHa3hiZnBQRS9vZzJTcTFDUVNNbzNlN2Q2dWl2Szc3?= =?utf-8?B?QU9adnJJazRxcXlhNEpIKzg4QnpRclZtYUhYK3ljTTJWYXZPMHFiQVhrRnRt?= =?utf-8?B?QUY5VGlPU1pGQlhBN1Q0RHQ0VTdWUkhaNWJQTkRBbVhlUmFNV2tIU1k4M3o0?= =?utf-8?B?MGVHb2paTlp2YzY3b25HUTVHOTZoQWo0ZkJKRE5reVBobmRGTG9PZ1pXamd3?= =?utf-8?B?c2xMbktscEFsRnJha09URThRN2pvVXFhM3N5SVZwNFNQZ0hYbW9UdzB1OTBa?= =?utf-8?B?aEdieXNJd1gzM0tmL0xRWWZCeUxRejNGQklMWUl4UUVmZ2txZ1NPTkhaaFMv?= =?utf-8?B?MmxmZ3lEZGxtVGRyaURTUXR3UkhsZUdLK2JORmFJazF4YlR0MDhZSUJwQ3lt?= =?utf-8?B?T3J3clZBRFZ6V0JDMFp4b3lwNEtieWUxdHhMd0lQZ1JPUlY1NGx4YXZOUnlD?= =?utf-8?B?MGFRbWVDUFU1SmZSVGkzUm1icTYwMDI2LytKOWtsYUZwbGR1eDdOdWZyaWNq?= =?utf-8?B?cklpT2EyYzE0Y0l3T3l1N3FQeko3UTBpTVlMRFVNTlowNW5oU0pQRFcvTWFr?= =?utf-8?B?Y3M1OHdzMlZEd2RkZG81NkErdFpja25uR2NGSEZsYkxmYUJ1cHpPTmhxWFBG?= =?utf-8?B?RStZV2RWclBNS0I3RnBxK1MydFZvVGwxRW4vcDVZeFEyYkIvSzY0YTFGQndB?= =?utf-8?B?UmljVTk4OWJrb2dzT1hSQTByMXVrRkFwUFlCZi8zVGVLL2RPNUliTUxtQlVn?= =?utf-8?B?aUl6ZUVhUEtwODZvRklqOXcralcycGlsOEtZVEZ4UEhLcjdySmo1Wjcxa3hO?= =?utf-8?B?OExWUzQ0RE9ad2E1OUo5RHA0Rm9wdGY4NTFqNmVqaXMxN2dINi83bUg4UkRy?= =?utf-8?B?WThxV0trV1VzQVlId1h5WEM4bDVwbzVzN0tkZmtJSXMyLy9rRFVyVFMxZ2F6?= =?utf-8?B?QXYzZWd5MEx0L1k2SVFwRTIvVlRCeERycS90TzY0Q09LL2lkdm9JUzEvR1U3?= =?utf-8?B?L0hJZjdwMUZLdGY4TFlXbTF1QXN3Z2xGTnR1RURBM2F5YVI3aXk4dEl5YjZx?= =?utf-8?B?QW1SSlFUanJGelZja2IyRi9tYXZzWmowdzduaVpLWHZJNlpYSHpXM1plMUJV?= =?utf-8?B?eGRXWnVvR3Y3dnU1R3JSMmh4K3NVcldSQ2dhWlJidGRUWmlFNVJNQ0RROWpZ?= =?utf-8?B?TkFlSHVvYk9ZR0JQcWozTmlmVEJETnVCYlZFanJWT1lQdC9Sam45NGloWWh3?= =?utf-8?B?SmVYZE8rSVRuRCtFVFpCSitoSE9jTWpITkVUL3NFQVVwKzFHWFZrYXBYTTNW?= =?utf-8?B?djhWS3EwNkhBTTdNc0N5Qm13Y2YxQXFHSlJHRW1lV1h0MkVuM0d4aHo4RHVY?= =?utf-8?B?dFJkQ1JMVnZhRzBCeVRhTWtYb0l0VUwrMGtwejVMQVFaL09ybnlEVWs2OWsw?= =?utf-8?B?L2kwZzVQNmJHNlU4RkNmYzhPbHVsMHY3S2Vya0N6bytHNTZKcy9WRVJqRXBE?= =?utf-8?B?cHVrQi9oeThob2RoZXdNMGVIdjlTc25vQjJQZXM1NGtLcWFaRnExcVdEUlkv?= =?utf-8?Q?qY7Bn/KiD10bN5utQ4Uh1o7dvhLdz2tMn98u0Kd?= X-MS-Exchange-CrossTenant-Network-Message-Id: 1f5aa6c1-d177-4827-9bc3-08d8c9f1bcb8 X-MS-Exchange-CrossTenant-AuthSource: DS7PR03MB5608.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Feb 2021 16:18:56.5651 (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: pXCnKu+NoZLzgJh2niRI28REGytsiaIGksCkC4Lrl398eZX3lhMqO5352f2Sz5MU2W6TOsKMS9AR4U8QivLcFg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR03MB4603 X-OriginatorOrg: citrix.com On Fri, Feb 05, 2021 at 05:13:22PM +0100, Jan Beulich wrote: > On 05.02.2021 16:43, Roger Pau Monné wrote: > > On Thu, Jan 14, 2021 at 04:04:11PM +0100, Jan Beulich wrote: > >> The "guest" variants are intended to work with (potentially) fully guest > >> controlled addresses, while the "unsafe" variants are not. > > > > Just to clarify, both work against user addresses, but guest variants > > need to be more careful because the guest provided address can also be > > modified? > > > > I'm trying to understand the difference between "fully guest > > controlled" and "guest controlled". > > Not exactly, not. "unsafe" means access to anything which may > fault, guest controlled or not. do_invalid_op()'s reading of > the insn stream is a good example - the faulting insn there > isn't guest controlled at all, but we still want to be careful > when trying to read these bytes, as we don't want to fully > trust %rip there. Would it make sense to threat everything as 'guest' accesses for the sake of not having this difference? I think having two accessors it's likely to cause confusion and could possibly lead to the wrong one being used in unexpected contexts. Does it add a too big performance penalty to always use the most restrictive one? Thanks, Roger.