Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Received-SPF: Pass (protection.outlook.com: domain of amd.com designates
 165.204.84.17 as permitted sender) receiver=protection.outlook.com;
 client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C
From:   Nikunj A Dadhania <nikunj@amd.com>
To:     <linux-kernel@vger.kernel.org>, <x86@kernel.org>
CC:     <bp@alien8.de>, <thomas.lendacky@amd.com>,
        <dionnaglaze@google.com>, <pgonda@google.com>, <seanjc@google.com>,
        <pbonzini@redhat.com>, <nikunj@amd.com>
Subject: [PATCH v3 11/14] x86/sev: Prevent RDTSC/RDTSCP interception for Secure TSC enabled guests
Date:   Sat, 22 Jul 2023 16:49:06 +0530
Message-ID: <20230722111909.15166-12-nikunj@amd.com>
In-Reply-To: <20230722111909.15166-1-nikunj@amd.com>
References: <20230722111909.15166-1-nikunj@amd.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Jul 2023 11:20:51.1073
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 7beb562b-4885-46ed-b9c0-08db8aa5b4df
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB04.amd.com]
X-MS-Exchange-CrossTenant-AuthSource: DM6NAM11FT098.eop-nam11.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY8PR12MB7243
X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,
        RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE,
        T_SCC_BODY_TEXT_LINE,URIBL_BLOCKED autolearn=no 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

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 3a5b0c9c4fcc..1c22025b298f 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -912,6 +912,13 @@ 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)
+		return ES_VMM_ERROR;
+
 	ret = sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, 0, 0);
 	if (ret != ES_OK)
 		return ret;
-- 
2.34.1