[PATCH 02/26] x86/tdx: Extend the cc_platform_has() API to support TDX guests

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Confidential Computing (CC) features (like string I/O unroll support,
memory encryption/decryption support, etc) are conditionally enabled
in the kernel using cc_platform_has() API. Since TDX guests also need
to use these CC features, extend cc_platform_has() API and add TDX
guest-specific CC attributes support.

Use is_tdx_guest() API to detect for the TDX guest status and return
TDX-specific CC attributes. To enable use of CC APIs in the TDX guest,
select ARCH_HAS_CC_PLATFORM in the CONFIG_INTEL_TDX_GUEST case.

This is a preparatory patch and just creates the framework for adding
TDX guest specific CC attributes.

Since is_tdx_guest() function (through cc_platform_has() API) is used in
the early boot code, disable the instrumentation flags and function
tracer. This is similar to AMD SEV and cc_platform.c.

Since intel_cc_platform_has() function only gets triggered when
is_tdx_guest() is true (valid CONFIG_INTEL_TDX_GUEST case), remove the
redundant #ifdef in intel_cc_platform_has().

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/Kconfig              | 1 +
 arch/x86/kernel/Makefile      | 3 +++
 arch/x86/kernel/cc_platform.c | 9 ++++-----
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a61ac6f8821a..8e781f166030 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -877,6 +877,7 @@ config INTEL_TDX_GUEST
 	bool "Intel TDX (Trust Domain Extensions) - Guest Support"
 	depends on X86_64 && CPU_SUP_INTEL
 	depends on X86_X2APIC
+	select ARCH_HAS_CC_PLATFORM
 	help
 	  Support running as a guest under Intel TDX.  Without this support,
 	  the guest kernel can not boot or run under TDX.
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 64f9babcfd95..8c9a9214dd34 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -22,6 +22,7 @@ CFLAGS_REMOVE_early_printk.o = -pg
 CFLAGS_REMOVE_head64.o = -pg
 CFLAGS_REMOVE_sev.o = -pg
 CFLAGS_REMOVE_cc_platform.o = -pg
+CFLAGS_REMOVE_tdx.o = -pg
 endif
 
 KASAN_SANITIZE_head$(BITS).o				:= n
@@ -31,6 +32,7 @@ KASAN_SANITIZE_stacktrace.o				:= n
 KASAN_SANITIZE_paravirt.o				:= n
 KASAN_SANITIZE_sev.o					:= n
 KASAN_SANITIZE_cc_platform.o				:= n
+KASAN_SANITIZE_tdx.o					:= n
 
 # With some compiler versions the generated code results in boot hangs, caused
 # by several compilation units. To be safe, disable all instrumentation.
@@ -50,6 +52,7 @@ KCOV_INSTRUMENT		:= n
 
 CFLAGS_head$(BITS).o	+= -fno-stack-protector
 CFLAGS_cc_platform.o	+= -fno-stack-protector
+CFLAGS_tdx.o		+= -fno-stack-protector
 
 CFLAGS_irq.o := -I $(srctree)/$(src)/../include/asm/trace
 
diff --git a/arch/x86/kernel/cc_platform.c b/arch/x86/kernel/cc_platform.c
index cc1ffe710dd2..e291e071aa63 100644
--- a/arch/x86/kernel/cc_platform.c
+++ b/arch/x86/kernel/cc_platform.c
@@ -12,14 +12,11 @@
 #include <linux/mem_encrypt.h>
 
 #include <asm/processor.h>
+#include <asm/tdx.h>
 
-static bool __maybe_unused intel_cc_platform_has(enum cc_attr attr)
+static bool intel_cc_platform_has(enum cc_attr attr)
 {
-#ifdef CONFIG_INTEL_TDX_GUEST
 	return false;
-#else
-	return false;
-#endif
 }
 
 /*
@@ -67,6 +64,8 @@ bool cc_platform_has(enum cc_attr attr)
 {
 	if (sme_me_mask)
 		return amd_cc_platform_has(attr);
+	else if (is_tdx_guest())
+		return intel_cc_platform_has(attr);
 
 	return false;
 }
-- 
2.32.0