Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
Message-ID: <8bd907ec-3f91-2e3d-de7c-ef753a005ea7@amd.com>
Date:   Mon, 30 Oct 2023 15:32:21 -0500
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.15.1
Subject: Re: [PATCH v5 11/14] x86/sev: Prevent RDTSC/RDTSCP interception for
 Secure TSC enabled guests
Content-Language: en-US
To:     Nikunj A Dadhania <nikunj@amd.com>, linux-kernel@vger.kernel.org,
        x86@kernel.org, kvm@vger.kernel.org
Cc:     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>
 <20231030063652.68675-12-nikunj@amd.com>
From:   Tom Lendacky <thomas.lendacky@amd.com>
In-Reply-To: <20231030063652.68675-12-nikunj@amd.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?NkdaamVmS0RRVkxCQ25KWEFSR1F5NldtSmJiWFZqcldZcjFFU09CQVZ2VTdq?=
 =?utf-8?B?ekdVSFMvTndYbkRJSndOVStWd3lXdnFoa2NEMHNPcldXZWh0MzdkNWM3L2lQ?=
 =?utf-8?B?NmJyenVnOFh4dkFlcTFtSHhwTHV1V3c1ZkZMT1JVaEJBR3ZTV2RiZnhYMzNH?=
 =?utf-8?B?SzlLcnRPVmZSdWZOSW5kSStHb1IxaG5kUjliQlJNRWFXNzNER1ZzeXZWU2sx?=
 =?utf-8?B?c2h2Z3hvVnpUd1hhRmtuSVVNaE10VWFtY3U0L2FCWXRjR3hSYkdNVDRMbERU?=
 =?utf-8?B?Lzc0TWYzWVBheWtUMXNValNiYWdqYVZYUW40b2ZoSzRmYjMvODJNMG4yMFB4?=
 =?utf-8?B?aVU3WnR1dFlIekNzZnNIRUFyUWJ2azNjRDlLRDl4ck1peUhYamxMK3hYZzZh?=
 =?utf-8?B?Q09QOWhxWm9zQlVrQ01TeEdwbFJhRWdtY3pPdjlnS0ViMUFLTlRzSmxEWWNY?=
 =?utf-8?B?SndXN2IzS0ZOOFZZbjVHRU1nQ2VuSEx3aUJ6SUtORzV3cVAzT3lJMFB0ZnNq?=
 =?utf-8?B?aVFqTUVwWXR2Y3RDTHdjaEFSQVJ6K2QwWVc4SWZ6d3NIRHBWck9NaVo4ZzRJ?=
 =?utf-8?B?NzdzeC8vN1VlT1ZKRU1Lb2wrQS9EbU1mRmZHYzliZHVqdWVRQU12VWpzNmpI?=
 =?utf-8?B?bzdMZWYwbGtMVzl5YjRLWUxWZzdSNmg1MGlOOTZmMGlKaXRMOHBPOGlabURW?=
 =?utf-8?B?eExXOEZ1TjNCUEtMTVFDUHNPSGJzK3BNOHNtdVdPM1RNaTkvdEtvRWQrVnBU?=
 =?utf-8?B?OUhqNzkzVHVYSm1VLzJ6eXFlWDNQaDF0N3VnZExvNUxBTnNFU1IyNVBLU1FR?=
 =?utf-8?B?UkR0VldjMHlRdUY5akRONk11SnJoYnFFTlpzbW84NU5tUXluNkZuaWhCbU55?=
 =?utf-8?B?V2RuV3cxRzJrQkR2dnJ2MFJ1dWp0MFlTZ3U1RUlaL0hDdU9uc0NJWEJhS3RE?=
 =?utf-8?B?alY4ZHVRWXVUVmsvb1ZCOVZvNlMwdmhjbUtrWUxmQVV2UHZNdG5WWFRPdS95?=
 =?utf-8?B?TkxoYldad3FrZXhmWjE3VnZsTFg2YWJNNTU2QkMvbTNkcUN0dzk5SVozSzVu?=
 =?utf-8?B?OWNtMGgrZjlrYVYyWEhsTXdLYmNCcDExQ1pKSFpOemljVnNqOEFXSk9yU285?=
 =?utf-8?B?YmZLYldCczIxeUFmeUEvcncyNWJKV0FFNTdjNTNlZVhqSkVmbjY2c1ZlaEQr?=
 =?utf-8?B?SlZSOURDemNSYTR5ZjJPempjVDFBcmhSakdrakN5Y1FqSHdVZG51blFSU1lS?=
 =?utf-8?B?V0lWb2sySlVubmU3VGtiNktocHJsb2Z1Q1ZUTTh6QzFieDZSU1JuRFdKN2Ni?=
 =?utf-8?B?VmhTRE1FTkg3YkZXSE5ZWExtMFdEY0w5T3VaZWIzVnM2cHNlUUpZZjZUZU55?=
 =?utf-8?B?UzRLNWR3azRNa2o3Y2EyMGhhcUpOTnJ1ejdNQkFydzRPLytKZXB0SXJGTi9v?=
 =?utf-8?B?TjhrSjFXeFV4Wm5CNFpadlBlUk9nOEF3NzhyY1VGRHFUd01JdjJybjBCZjlK?=
 =?utf-8?B?VnlSQ2dVNm82ZWhQY01hNWlaZktzSkNpQzB2ZU1jRVphSG5rcG1STkxvNE5n?=
 =?utf-8?B?ZGNLaTUvU2dRRGtTUE5QRS84bExFajJvcjYvVTV5SVF0KzE2NERJaE40QTN4?=
 =?utf-8?B?VVc1emViVFF2cFhXaWp6dFN2M2sxREJFREgrR2tldmVxQlQ4bVk2QVJ5WEV6?=
 =?utf-8?B?RnJxbEZPaG53NzBxbkpZTnZNcVdyRWgrLzg4UXpYckJpNlBXMXp5bkdDMXJK?=
 =?utf-8?B?bEc4WXRidS9ZR09nUitoMk9CTDU2d01uQ05PbFpJQm5jd09JQ1NPZlVYZm9w?=
 =?utf-8?B?d0JtZVI1eU1PNXVJalV4dCt6TEdwdXZVQnJOYW4vZG1GSTZPbm12RHJIRnNZ?=
 =?utf-8?B?TnhiTFRqa3l1YnMwSVViUWc1bTdUSGNiQkxJZlhBZU81WDZWYmtNRlB6bDg5?=
 =?utf-8?B?V1lZZnBJdUIzY0FzQkhlcUFMREgweGc4bE9DdFpoZEJSelhvTkloSXpOWEZo?=
 =?utf-8?B?SDZjaEZJL1AxWDlLWUthM0VyMUp4QmM2RGpzb0lyQ3dhYzRZT2U1TXFBMmdm?=
 =?utf-8?B?aUZVQUxWYmpjTm41VjdCSm0rcEZXMHphNmlWYmExMS8yY25qQUVTcEZiZXdz?=
 =?utf-8?Q?DGthq0MWwyh39usjkX9Q4joSF?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 560c87cf-4215-450d-a552-08dbd9875337
X-MS-Exchange-CrossTenant-AuthSource: BL1PR12MB5732.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Oct 2023 20:32:24.5407
 (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: ENrYkiHl2sTVBUgyPqqOsI3GsbA8pdfCEBulORlmQ7NiA0/r28eAIxp7NB8hwIiamkpeYc7cmbhX0fbBnXhBQQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB7022
X-Spam-Status: No, score=-6.0 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
        DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,
        NICE_REPLY_A,RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,
        SPF_NONE autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
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 (snail.vger.email [0.0.0.0]); Mon, 30 Oct 2023 13:32:44 -0700 (PDT)

On 10/30/23 01:36, Nikunj A Dadhania wrote:
> The hypervisor should not be intercepting RDTSC/RDTSCP when Secure TSC
> is enabled. A #VC exception will be generated if the RDTSC/RDTSCP
> instructions are being intercepted. If this should occur and Secure
> TSC is enabled, terminate guest execution.
> 
> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
> ---
>   arch/x86/kernel/sev-shared.c | 7 +++++++
>   1 file changed, 7 insertions(+)
> 
> diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
> index ccb0915e84e1..833b0ae38f0b 100644
> --- a/arch/x86/kernel/sev-shared.c
> +++ b/arch/x86/kernel/sev-shared.c
> @@ -991,6 +991,13 @@ static enum es_result vc_handle_rdtsc(struct ghcb *ghcb,
>   	bool rdtscp = (exit_code == SVM_EXIT_RDTSCP);
>   	enum es_result ret;
>   
> +	/*
> +	 * RDTSC and RDTSCP should not be intercepted when Secure TSC is
> +	 * enabled. Terminate the SNP guest when the interception is enabled.
> +	 */
> +	if (sev_status & MSR_AMD64_SNP_SECURE_TSC)

If you have to use sev_status, then please document why cc_platform_has() 
can't be used in the comment above.

Thanks,
Tom

> +		return ES_VMM_ERROR;
> +
>   	ret = sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, 0, 0);
>   	if (ret != ES_OK)
>   		return ret;