[PATCH v2 04/12] x86/x86: Add early_is_tdx_guest() interface

Kuppuswamy Sathyanarayanan
2021-06-12T21:05:57Z

Add helper function to detect TDX feature support. It will be used
to protect TDX specific code in decompression code.

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---

Changes since v1:
* Removed is_tdx_guest() interface. We will rely on
prot_guest_has(PR_GUEST_TDX) for TDX related checks.
* Renamed is_tdx_guest() to early_is_tdx_guest() as per
review suggestion.
* Fixed commit title and log to reflect above changes.
* Simplified native_cpuid_has_tdx_guest() as per review suggestion.

arch/x86/boot/compressed/Makefile | 1 +
arch/x86/boot/compressed/tdx.c | 28 ++++++++++++++++++++++++++++
2 files changed, 29 insertions(+)
create mode 100644 arch/x86/boot/compressed/tdx.c

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 431bf7f846c3..22a2a6cc2ab4 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -98,6 +98,7 @@ ifdef CONFIG_X86_64
endif

vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o
+vmlinux-objs-$(CONFIG_INTEL_TDX_GUEST) += $(obj)/tdx.o

vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
efi-obj-$(CONFIG_EFI_STUB) = $(objtree)/drivers/firmware/efi/libstub/lib.a
diff --git a/arch/x86/boot/compressed/tdx.c b/arch/x86/boot/compressed/tdx.c
new file mode 100644
index 000000000000..ddfa4a6d1939
--- /dev/null
+++ b/arch/x86/boot/compressed/tdx.c
@@ -0,0 +1,28 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * tdx.c - Early boot code for TDX
+ */
+
+#include <asm/tdx.h>
+
+static int __ro_after_init tdx_guest = -1;
+
+static inline bool native_cpuid_has_tdx_guest(void)
+{
+ u32 eax = TDX_CPUID_LEAF_ID, sig[3] = {0};
+
+ if (native_cpuid_eax(0) < TDX_CPUID_LEAF_ID)
+ return false;
+
+ native_cpuid(&eax, &sig[0], &sig[1], &sig[2]);
+
+ return !memcmp("IntelTDX ", sig, 12);
+}
+
+bool early_is_tdx_guest(void)
+{
+ if (tdx_guest < 0)
+ tdx_guest = native_cpuid_has_tdx_guest();
+
+ return !!tdx_guest;
+}
--
2.25.1