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X-MS-Exchange-AntiSpam-MessageData: =?utf-8?B?UGU3Wk1wT2JXWDNkbm03djFQSFJWSjFPSy9lbG8zSDdNektWVlUxLzdHbHBh?= =?utf-8?B?WDUzeS9teGFrSlJwczQ2aWZ4SC9Qd3RHVEdmL0t6akM2SzEwanZqem5QSGpB?= =?utf-8?B?dUwzNllNTm5HaU1aOHE1bE5WcEZnWU1veEZibDJYWjV1TjdCYzA0cFFvZ3Y5?= =?utf-8?B?K0FRcmQ2N1pkeXU3bEJXbjcwSFE5S3Z2eFdzUlNYS09NdlFoaTA4ekdQbWRY?= =?utf-8?B?S09sMnc2UnRSSnFuNGlhUHNZSUdMdUVDY1Fld1NIWGVMQmw0eE9EMDIzL3Vh?= =?utf-8?B?V3ppQ3RTR3F3NjA0QXJvNmorZEczbUF1TjJuWHYzSFJyS0tLSHNJWkl4Vitr?= =?utf-8?B?V04zNGx2WW9CMGVldDZnanBBTW42eXBCbWlFaFZjSEsvZVhseEdZbGtiNEJ5?= =?utf-8?B?NWM3UEltdUpRNmNldXlQNE5lbStGMkZYMmZyUmdMSUFKZDQwWFVJdGxzRzdB?= =?utf-8?B?aHFVelRhaHh4U0pPU1UyVE12Qmg1NFRtdzhCbW9lK2hGSFpzYWpFWDdYQ1Jw?= =?utf-8?B?Wjc5c2R2aE1abU05TXVlVWhFbk5XdE10Z1NBM0xKQVc2ZmdkeHMzam5mYS9C?= =?utf-8?B?dU5ZRklrSUdLTm1xV1VDUWFxVWsyWEZuajVRdndNWU5GaTRKanVlZk9VVjJI?= =?utf-8?B?aUJEUXZPRy9Wazdoc0ZIQjdlT0xyRlBwWmZkN25ZTkpCWHJBZnlrOHIrYlAw?= =?utf-8?B?bnl2TU00S1MySGQ0RUVSRHpPRU45a0FsQitCS2ROOUJCaWt4ZkVrRjhhbGtR?= =?utf-8?B?aDI1V3ZQVGI4bkpLd2Q3N1Y1QklkdzR5QWw2QjlnWDA1UFBWU1ZCdURPcG5j?= =?utf-8?B?M2NUZDVDWDlQUTVjU1U4a2dPeGJVRTlGV1lNVVUyU1hrQ1RoQy9xc3dRalNk?= =?utf-8?B?cXBETHJ3Qkx2blI4bk5SMDMvczJucElyS3A4bVFSL2JwQ0h1SUVCTWVaa0d0?= =?utf-8?B?Rk95TlEzNU8rVVRudi9kTVNWMjhOV2RrNG1OYWUvVk94cmcxMGQvU0NNblo2?= =?utf-8?B?bmRBaWV6d3lPVWthRGRJVWo3VWR1UzA4TUpYMHArTGZQbm5obVBVemFuWWZK?= =?utf-8?B?UjhHNTJONjJGbUZoWHMya0wyMnpYbWdrNUdxbzdIaFlieGpZTXRZdWpLVEFN?= =?utf-8?B?bnJ4dFdCNnRzeFZNb0szVzZUSFJlL2t3MU1ibVFNa0RxOTZPOFdjOXFLdEFR?= =?utf-8?B?cVRWS1U2U1RsNmtDd2puL1p4SEp3Si8rV05sVDVIeEFUME5SUmFxMlBRVWpY?= =?utf-8?B?YUlCV3BTcW5FNHpzRld5Sno0MmNxNWtES3k4aGUyRFRjaWlCT1dkNjc5Z290?= =?utf-8?B?Z2xsZTJoRkVzM2Q1YThMSTN0MUVaNGd0UWRaa3NRcFNJK05TYWREWGVERVdW?= =?utf-8?B?VFo0M0orOHdMNmFTSVBNU2JvZDFEZDRFbkgrOExhRTd3SnVCcDVoTjJLRytu?= =?utf-8?B?RWwwVFl3b2UyQ3F3ZG9oM0o3UmUvd3Ruekc5N1Y0ei9FblZkbklZZE5ZUkx4?= =?utf-8?B?VXc5SnRrKzkzeS9WR0hhUEw5L3p3Y1dSUEUreStnVGhrSEZQM1AzSnNISjJU?= =?utf-8?B?Yi9XV1hqQUJWOU5TWnZNZ0N5NnFSRlA1Y0lYa0wvM0ZvakpSM1dNMFBnQWpX?= =?utf-8?B?eHpkR0ltRkFYcS9vV3RYTXhSVXQyNjVRakJ6MDJzYUpOdW1KZGd2Y2lac1J1?= =?utf-8?B?WWFuUDN3S2RyTUtNY2NoaFZrMUNsQXc3ZUNhUmYyN1VlVkw5UUE3UHJUZzdG?= =?utf-8?Q?9aRJEQZOxF8qrC2Yya6cwdrvZVhcpnwOXPfXBa4?= X-MS-Exchange-CrossTenant-Network-Message-Id: f39bcf40-6f10-4b43-a480-08d9032bf917 X-MS-Exchange-CrossTenant-AuthSource: DS7PR03MB5608.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 Apr 2021 12:09:24.8742 (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: HLihlHaNlHbOubSvi9cc3C1br7hL2MfN18IgYfbUR8h9MnDpHLdVQk+EmG3NhSA92YoWMntJ/LXLsFIVPYDFjA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR03MB4220 X-OriginatorOrg: citrix.com On Mon, Apr 19, 2021 at 01:46:02PM +0200, Jan Beulich wrote: > On 19.04.2021 11:16, Roger Pau Monné wrote: > > Adding Paul also for the Viridian part. > > > > On Fri, Apr 16, 2021 at 03:16:41PM +0200, Jan Beulich wrote: > >> Zapping leaf data for out of range leaves is just one half of it: To > >> avoid guests (bogusly or worse) inferring information from mere leaf > >> presence, also shrink maximum indicators such that the respective > >> trailing entry is not all blank (unless of course it's the initial > >> subleaf of a leaf that's not the final one). > >> > >> This is also in preparation of bumping the maximum basic leaf we > >> support, to ensure guests not getting exposed related features won't > >> observe a change in behavior. > >> > >> Signed-off-by: Jan Beulich > >> --- > >> v3: Record the actual non-empty subleaf in p->basic.raw[0x7], rather > >> than subleaf 0. Re-base over Viridian leaf 40000005 addition. > >> v2: New. > >> > >> --- a/tools/tests/cpu-policy/test-cpu-policy.c > >> +++ b/tools/tests/cpu-policy/test-cpu-policy.c > >> @@ -8,10 +8,13 @@ > >> #include > >> > >> #include > >> +#include > >> #include > >> #include > >> #include > >> > >> +#define XSTATE_FP_SSE (X86_XCR0_FP | X86_XCR0_SSE) > >> + > >> static unsigned int nr_failures; > >> #define fail(fmt, ...) \ > >> ({ \ > >> @@ -553,6 +556,103 @@ static void test_cpuid_out_of_range_clea > >> } > >> } > >> > >> +static void test_cpuid_maximum_leaf_shrinking(void) > >> +{ > >> + static const struct test { > >> + const char *name; > >> + struct cpuid_policy p; > >> + } tests[] = { > >> + { > >> + .name = "basic", > >> + .p = { > >> + /* Very basic information only. */ > >> + .basic.max_leaf = 1, > >> + .basic.raw_fms = 0xc2, > >> + }, > >> + }, > >> + { > >> + .name = "cache", > >> + .p = { > >> + /* Cache subleaves present. */ > >> + .basic.max_leaf = 4, > >> + .cache.subleaf[0].type = 1, > > > > On a private conversation with Andrew he raised the issue that the > > shrinking might be overly simplistic. For example if the x2APIC > > feature bit in leaf 1 is set then the max leaf should be at least 0xb > > in order to be able to fetch the x2APIC ID, even if it's 0. > > But in such a case the "type" field of leaf 0xb's first sub-leaf is > going to be non-zero, isn't it? Right, as type 0 is invalid according to Intel SDM, so you will never be able to shrink below 0xb while having x2APIC set. I still wonder however if there's any other such dependency, where shrinking the max cpuid leaf could force us to drop features exposed in inferior leaves. > > I also wonder if we are shrinking the leaves too much, for example we > > should always report up to 0x40000000 (or 0x40000100) plus the Xen > > leaves, as we never hide those and it's also documented in the public > > headers? > > Not sure I follow - I'm likely confused by you quoting 0x40000000 > and 0x40000100 rather than 0x400000nn and 0x400001nn, as elsewhere > you suggested we may not want to clip sub-leaves there. Can you > clarify whether you really mean only the first sub-leaves (each) > here, and if so why you say "up to"? Furthermore for the Xen leaves > I don't think I do excessive clipping ... No, sorry, I was confused. What you do is fine, I would even (as said in the previous patch) just report the max leaf unconditionally even if empty, as we are not leaking any hardware state in this case. Thanks, Roger.