Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) client-ip=23.128.96.35;
Message-ID: <5d8040b2-c761-4cea-a2ec-39319603e94a@amd.com>
Date:   Thu, 2 Nov 2023 17:37:36 +0530
User-Agent: Mozilla Thunderbird
Reply-To: nikunj@amd.com
Subject: Re: [PATCH v5 13/14] x86/tsc: Mark Secure TSC as reliable clocksource
Content-Language: en-US
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc:     Dave Hansen <dave.hansen@intel.com>, linux-kernel@vger.kernel.org,
        thomas.lendacky@amd.com, x86@kernel.org, kvm@vger.kernel.org,
        bp@alien8.de, mingo@redhat.com, tglx@linutronix.de,
        dave.hansen@linux.intel.com, dionnaglaze@google.com,
        pgonda@google.com, seanjc@google.com, pbonzini@redhat.com
References: <20231030063652.68675-1-nikunj@amd.com>
 <20231030063652.68675-14-nikunj@amd.com>
 <57d63309-51cd-4138-889d-43fbdf5ec790@intel.com>
 <ae267e31-5722-4784-9146-28bb13ca7cf5@amd.com>
 <20231102103306.v7ydmrobd5ibs4yn@box.shutemov.name>
From:   "Nikunj A. Dadhania" <nikunj@amd.com>
In-Reply-To: <20231102103306.v7ydmrobd5ibs4yn@box.shutemov.name>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?R0xsMXVtNjFkbzRwcXJScnhlb0hsN05OVWVjSFBJRXQrZWZNSmdVR0U3L1Zw?=
 =?utf-8?B?eW5ZUEhTQ2s5cWxXR1NsWTR5bGNtQmhkU1NLbVFCOU1DUDBxVjRZRXFTVmdt?=
 =?utf-8?B?ZVJ4N2hpbTRFTDh3cVBLZDBoeXRzN2lDbGFPeStJeW9zMk4vNWE2S29DR054?=
 =?utf-8?B?Z1kwU0k4VlJUSFZTOENjeFgyTXNCQW0zYlNJOFpISjkwakV0RncwUkZPbHZF?=
 =?utf-8?B?bExEZVd6dmM0dHdzQkwvTWpxdnRqREM0SFZqMkY4QzVpaDR5bFZINk1laUhr?=
 =?utf-8?B?K0xqRyt4OEY4U25SYVRYQzRkaklGdmtNNUpmUXhQZHpPbzMzbUJtUk9ZSEhz?=
 =?utf-8?B?a2YwbXArREtxNW9OS2Q5TG0zMHM4YS9uRGZlK1hUSFVzSk1XTElqdm1QUnV6?=
 =?utf-8?B?N05qejlxeStkWkJ1ZXZ1ODZqR3BwZ3NNY2pxMXA3TjRRQkl3dG9NcTdnWks4?=
 =?utf-8?B?NHVycUM0OUhEM3ZTRHhBR2g5OUs5dm5IWjF5MFVYdnlxYzZPd01GZ3V3eitz?=
 =?utf-8?B?VVdvamhpT1VTMWs0SDF1QlJ3U3NlSTJvWXN0NUcxekdqL2EwRFA2ejBCR0tQ?=
 =?utf-8?B?UDZ6aEJtaXdVR1g3U1owMWxBZXJtMmg4UEw1RTgzOW9ZU0NTTWZPeS93eFc4?=
 =?utf-8?B?ZTVhK2VPSFBWM2NSOTBQWTdJdWhnMi9ZVldDVjB3V0ZIY0VHUjQxMkcxMFF2?=
 =?utf-8?B?dHh0ZlloZjdTQ2plRFdwOXlFRFJyRE85c0tZc1VmSkIvQldqMWh6ZjR1Z3c0?=
 =?utf-8?B?ekdCSzFlek1US0dVY2hIaWtsY1BNWWRmcmxpSHd0M3IxRE1FUUZJMm9RRDRo?=
 =?utf-8?B?clhQelpIVGYrV3N0RmNZUzVOUFJqK3RTdTdKdTJyeEdOMlhjZ3ZqcU93cUhu?=
 =?utf-8?B?eUpweTlJMzFSTGVBQjF5MXpIMldvZ0hVOGgwSDNPTlptbFpwMEN4T2dsdzlR?=
 =?utf-8?B?MlViU09nc0RZUnorMXVHYlFBYkx2a21pbWZMMWF3SXhCSUhlcDZJRHVKTy9z?=
 =?utf-8?B?U2lFaXVkTWM4VnZodTRCQXhWc2cydk1EMXpNUmdEem53UUVTNlVtMVpNblMr?=
 =?utf-8?B?QjgrOE9LM3NjUzJuUmh1VmovTzdIR2ZyOEQ1TmdGTXRkbndsQnY0RGFDc29u?=
 =?utf-8?B?K0dhVWlvV29GZFdYUnJyY2Z1VlRFeUJtSjlYRTJ5NDhOMm52THYzNDRsSHZX?=
 =?utf-8?B?RVBIWUR4WWhGeEhWK1g3YUQwTUk5ZjR3TlEyUUpDNng2cE5yUWlEdGxsRTk5?=
 =?utf-8?B?QWs5TmNvM0J1NGVGSDF0aUwxQ1MrR3QzVXRidnp4dU9saUZFaVp0SnBLQVp2?=
 =?utf-8?B?c1BuTTBMMmZJL0JlcFB1Wk5BdTFyQlhQYlJaWTkyUUgwVStoWEhpci9GemEw?=
 =?utf-8?B?bWhTQmlpR29YaFI4WXpDaHRzTWlpdkh0UVRyVFZqWXFIa3pGTDdZazM3Tndy?=
 =?utf-8?B?RVlneEdZRk56ZFM5emQrQXRKaWZMNmY2YTNTME1vRmV0WHBkeW1WaDRMRTVp?=
 =?utf-8?B?UXlzN0ZUY3I5dlp6cm9YVjIySEx2YUtsSXNYT3FCM1lDSXR5N1VkV2JMcmlh?=
 =?utf-8?B?ek9YekJVNStWWGp6YVE1SGVGaTgvYVNOSG0vMk9ZRjIxWDlSWHhCNk5hZ0p5?=
 =?utf-8?B?ZUJjcDBSSk43enFlYTZ3cHJhSk9hbms1VVVWcExSV2tvZllvMEdCMksyV1Ba?=
 =?utf-8?B?S0p0Mm5RYjBGQkFTa25OeGROVkVJbXBQSXJCUzltTW0rM0oycXF0QS9RTWJD?=
 =?utf-8?B?SVhObkFUdGhydHRsVnpzTGlMY1lsSVIyeUlsaGsvaXNTaHRJT1JYZlNtWVRn?=
 =?utf-8?B?bm9kOTJPZkllK3hKQnZCY0tJczZqaEtUR0xSZ1FJb3pFTXVMRWtzRTI1Q2pF?=
 =?utf-8?B?NlJpUnUrUXpEdzZXY3lQcW1Pb3dJVktaTWdVa3lvSUMxYVhtWTgvYkVnVVFO?=
 =?utf-8?B?ZEE5N3BhOTBZbTRSSFhxSEVKZXlrQ3lMM3R3ZE9mZ1l6M1FBaXZXZXhFaEEx?=
 =?utf-8?B?S08vczlsUDY2Yms2ek9kZmN1NWdvWk00ZGtDZ3BLcjZORlloL1RZZ05OS1VD?=
 =?utf-8?B?KzVKdkdXdE1hUlhEdWx5dTMrNEF2c1dOZ0MzanM5ZDZ0TDVPODBRS2ZCY3cr?=
 =?utf-8?Q?bFzd5pocEJ1J6/KQVWqgEKD0J?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 64657847-66b6-44b3-2535-08dbdb9c5462
X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB6309.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 02 Nov 2023 12:07:48.4070
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: L+GkXbwAh0sGJLC7hOfprGdCFwNuKLTYfGTum9Mo/+vwi3a9nRfZEhE0TkDcQ+ScuqClrEmXHVPiT5+qNFygzQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR12MB6829
X-Spam-Status: No, score=-1.3 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE,
	URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on groat.vger.email
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (groat.vger.email [0.0.0.0]); Thu, 02 Nov 2023 05:08:16 -0700 (PDT)

On 11/2/2023 4:03 PM, Kirill A. Shutemov wrote:
> On Thu, Nov 02, 2023 at 11:23:34AM +0530, Nikunj A. Dadhania wrote:
>> On 10/30/2023 10:48 PM, Dave Hansen wrote:
>>> On 10/29/23 23:36, Nikunj A Dadhania wrote:
>>> ...
>>>> diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
>>>> index 15f97c0abc9d..b0a8546d3703 100644
>>>> --- a/arch/x86/kernel/tsc.c
>>>> +++ b/arch/x86/kernel/tsc.c
>>>> @@ -1241,7 +1241,7 @@ static void __init check_system_tsc_reliable(void)
>>>>  			tsc_clocksource_reliable = 1;
>>>>  	}
>>>>  #endif
>>>> -	if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE))
>>>> +	if (boot_cpu_has(X86_FEATURE_TSC_RELIABLE) || cc_platform_has(CC_ATTR_GUEST_SECURE_TSC))
>>>>  		tsc_clocksource_reliable = 1;
>>>
>>> Why can't you just set X86_FEATURE_TSC_RELIABLE?
>>
>> Last time when I tried, I had removed my kvmclock changes and I had set
>> the X86_FEATURE_TSC_RELIABLE similar to Kirill's patch[1], this did not
>> select the SecureTSC.
>>
>> Let me try setting X86_FEATURE_TSC_RELIABLE and retaining my patch for
>> skipping kvmclock.
> 
> kvmclock lowers its rating if TSC is good enough:
> 
> 	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
> 	    boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
> 	    !check_tsc_unstable())
> 		kvm_clock.rating = 299;
> 
> Does your TSC meet the requirements?

I have set TscInvariant (bit 8) in CPUID_8000_0007_edx and TSC is set as reliable.

With this I see kvm_clock rating being lowered, but kvm-clock is still being picked as clock-source.

[    0.000834] kvmclock_init: lowering kvm_clock rating
[    0.002623] clocksource: kvm-clock: mask: 0xffffffffffffffff max_cycles: 0x1cd42e4dffb, max_idle_ns: 881590591483 ns
[    2.295082] clocksource: Switched to clocksource kvm-clock

Regards
Nikunj