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@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/all/20241104103803.195705-5-kirill.shutemov%40linux.intel.com

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 2f85ed0..0d9b090 100644 (file)
--- 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 (file)
--- 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