linux-kernel - [tip: x86/tdx] x86/tdx: Enable CPU topology enumeration

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Message-ID: <173100516336.32228.15253243612567317594.tip-bot2@tip-bot2>
Date: Thu, 07 Nov 2024 18:46:03 -0000
From: "tip-bot2 for Kirill A. Shutemov" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>, Kai Huang <kai.huang@...el.com>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/tdx] x86/tdx: Enable CPU topology enumeration

The following commit has been merged into the x86/tdx branch of tip:

Commit-ID:     7ae15e2f69bad06527668b478dff7c099ad2e6ae
Gitweb:        https://git.kernel.org/tip/7ae15e2f69bad06527668b478dff7c099ad2e6ae
Author:        Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
AuthorDate:    Mon, 04 Nov 2024 12:38:03 +02:00
Committer:     Dave Hansen <dave.hansen@...ux.intel.com>
CommitterDate: Thu, 07 Nov 2024 10:27:45 -08:00

x86/tdx: Enable CPU topology enumeration

TDX 1.0 defines baseline behaviour of TDX guest platform. TDX 1.0
generates a #VE when accessing topology-related CPUID leafs (0xB and
0x1F) and the X2APIC_APICID MSR. The kernel returns all zeros on CPUID
topology. In practice, this means that the kernel can only boot with a
plain topology. Any complications will cause problems.

The ENUM_TOPOLOGY feature allows the VMM to provide topology
information to the guest. Enabling the feature eliminates
topology-related #VEs: the TDX module virtualizes accesses to
the CPUID leafs and the MSR.

Enable ENUM_TOPOLOGY if it is available.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
Acked-by: Kai Huang <kai.huang@...el.com>
Link: https://lore.kernel.org/all/20241104103803.195705-5-kirill.shutemov%40linux.intel.com
---
 arch/x86/coco/tdx/tdx.c           | 27 +++++++++++++++++++++++++++
 arch/x86/include/asm/shared/tdx.h |  2 ++
 2 files changed, 29 insertions(+)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 2f85ed0..0d9b090 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -248,6 +248,32 @@ static void disable_sept_ve(u64 td_attr)
 		  TD_CTLS_PENDING_VE_DISABLE);
 }
 
+/*
+ * TDX 1.0 generates a #VE when accessing topology-related CPUID leafs (0xB and
+ * 0x1F) and the X2APIC_APICID MSR. The kernel returns all zeros on CPUID #VEs.
+ * In practice, this means that the kernel can only boot with a plain topology.
+ * Any complications will cause problems.
+ *
+ * The ENUM_TOPOLOGY feature allows the VMM to provide topology information.
+ * Enabling the feature  eliminates topology-related #VEs: the TDX module
+ * virtualizes accesses to the CPUID leafs and the MSR.
+ *
+ * Enable ENUM_TOPOLOGY if it is available.
+ */
+static void enable_cpu_topology_enumeration(void)
+{
+	u64 configured;
+
+	/* Has the VMM provided a valid topology configuration? */
+	tdg_vm_rd(TDCS_TOPOLOGY_ENUM_CONFIGURED, &configured);
+	if (!configured) {
+		pr_err("VMM did not configure X2APIC_IDs properly\n");
+		return;
+	}
+
+	tdg_vm_wr(TDCS_TD_CTLS, TD_CTLS_ENUM_TOPOLOGY, TD_CTLS_ENUM_TOPOLOGY);
+}
+
 static void tdx_setup(u64 *cc_mask)
 {
 	struct tdx_module_args args = {};
@@ -279,6 +305,7 @@ static void tdx_setup(u64 *cc_mask)
 	tdg_vm_wr(TDCS_NOTIFY_ENABLES, 0, -1ULL);
 
 	disable_sept_ve(td_attr);
+	enable_cpu_topology_enumeration();
 }
 
 /*
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index fecb2a6..89f7fca 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -23,12 +23,14 @@
 #define TDCS_CONFIG_FLAGS		0x1110000300000016
 #define TDCS_TD_CTLS			0x1110000300000017
 #define TDCS_NOTIFY_ENABLES		0x9100000000000010
+#define TDCS_TOPOLOGY_ENUM_CONFIGURED	0x9100000000000019
 
 /* TDCS_CONFIG_FLAGS bits */
 #define TDCS_CONFIG_FLEXIBLE_PENDING_VE	BIT_ULL(1)
 
 /* TDCS_TD_CTLS bits */
 #define TD_CTLS_PENDING_VE_DISABLE	BIT_ULL(0)
+#define TD_CTLS_ENUM_TOPOLOGY		BIT_ULL(1)
 
 /* TDX hypercall Leaf IDs */
 #define TDVMCALL_MAP_GPA		0x10001