[PATCH v3 3/6] x86/hyperv: Add hv_isolation_type_tdx() to detect TDX guests

[Dexuan Cui <decui@microsoft.com>]

No logic change to SNP/VBS guests.

hv_isolation_type_tdx() wil be used to instruct a TDX guest on Hyper-V to
do some TDX-specific operations, e.g. hv_do_hypercall() should use
__tdx_hypercall(), and a TDX guest on Hyper-V should handle the Hyper-V
Event/Message/Monitor pages specially.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

---

Changes in v2:
  Added "#ifdef CONFIG_INTEL_TDX_GUEST and #endif" for
    hv_isolation_type_tdx() in arch/x86/hyperv/ivm.c.

    Simplified the changes in ms_hyperv_init_platform().

Changes in v3:
  Added Kuppuswamy's Reviewed-by.

 arch/x86/hyperv/ivm.c              | 9 +++++++++
 arch/x86/include/asm/hyperv-tlfs.h | 3 ++-
 arch/x86/include/asm/mshyperv.h    | 3 +++
 arch/x86/kernel/cpu/mshyperv.c     | 7 ++++++-
 drivers/hv/hv_common.c             | 6 ++++++
 5 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 1dbcbd9da74d..13ccb52eecd7 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -269,6 +269,15 @@ bool hv_isolation_type_snp(void)
 	return static_branch_unlikely(&isolation_type_snp);
 }
 
+#ifdef CONFIG_INTEL_TDX_GUEST
+DEFINE_STATIC_KEY_FALSE(isolation_type_tdx);
+
+bool hv_isolation_type_tdx(void)
+{
+	return static_branch_unlikely(&isolation_type_tdx);
+}
+#endif
+
 /*
  * hv_mark_gpa_visibility - Set pages visible to host via hvcall.
  *
diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 08e822bd7aa6..1f4a967b48c5 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -163,7 +163,8 @@
 enum hv_isolation_type {
 	HV_ISOLATION_TYPE_NONE	= 0,
 	HV_ISOLATION_TYPE_VBS	= 1,
-	HV_ISOLATION_TYPE_SNP	= 2
+	HV_ISOLATION_TYPE_SNP	= 2,
+	HV_ISOLATION_TYPE_TDX	= 3
 };
 
 /* Hyper-V specific model specific registers (MSRs) */
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 6d502f3efb0f..49bca07bbd2c 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -14,6 +14,7 @@
 union hv_ghcb;
 
 DECLARE_STATIC_KEY_FALSE(isolation_type_snp);
+DECLARE_STATIC_KEY_FALSE(isolation_type_tdx);
 
 typedef int (*hyperv_fill_flush_list_func)(
 		struct hv_guest_mapping_flush_list *flush,
@@ -30,6 +31,8 @@ extern u64 hv_current_partition_id;
 
 extern union hv_ghcb * __percpu *hv_ghcb_pg;
 
+extern bool hv_isolation_type_tdx(void);
+
 int hv_call_deposit_pages(int node, u64 partition_id, u32 num_pages);
 int hv_call_add_logical_proc(int node, u32 lp_index, u32 acpi_id);
 int hv_call_create_vp(int node, u64 partition_id, u32 vp_index, u32 flags);
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 46668e255421..941372449ff2 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -339,9 +339,14 @@ static void __init ms_hyperv_init_platform(void)
 		}
 		/* Isolation VMs are unenlightened SEV-based VMs, thus this check: */
 		if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT)) {
-			if (hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE)
+			if (hv_get_isolation_type() == HV_ISOLATION_TYPE_VBS ||
+			    hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
 				cc_set_vendor(CC_VENDOR_HYPERV);
 		}
+
+		if (IS_ENABLED(CONFIG_INTEL_TDX_GUEST) &&
+		    hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX)
+			static_branch_enable(&isolation_type_tdx);
 	}
 
 	if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index ae68298c0dca..a9a03ab04b97 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -268,6 +268,12 @@ bool __weak hv_isolation_type_snp(void)
 }
 EXPORT_SYMBOL_GPL(hv_isolation_type_snp);
 
+bool __weak hv_isolation_type_tdx(void)
+{
+	return false;
+}
+EXPORT_SYMBOL_GPL(hv_isolation_type_tdx);
+
 void __weak hv_setup_vmbus_handler(void (*handler)(void))
 {
 }
-- 
2.25.1