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Date:   Mon,  4 Oct 2021 19:51:57 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>, Deep Shah <sdeep@...are.com>,
        VMware Inc <pv-drivers@...are.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Cc:     Peter H Anvin <hpa@...or.com>, Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v8 03/11] x86/cpufeatures: Add TDX Guest CPU feature

Add CPU feature detection for Trusted Domain Extensions support. TDX
feature adds capabilities to keep guest register state and memory
isolated from hypervisor.

For TDX guest platforms, executing CPUID(eax=0x21, ecx=0) will return
following values in EAX, EBX, ECX and EDX.

EAX:  Maximum sub-leaf number:  0
EBX/EDX/ECX:  Vendor string:

EBX =  "Inte"
EDX =  "lTDX"
ECX =  "    "

So when above condition is true, set X86_FEATURE_TDX_GUEST feature cap
bit.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
---

Changes since v7:
 * Add comments for the order of tdx_early_init() call.
 * Similar to AMD (sme_me_mask) added a global variable
   is_tdx_guest for Intel TDX related checks.
 * Changed pr_fmt from "x86/tdx: " to "tdx:"

 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/include/asm/tdx.h         | 22 ++++++++++++++++
 arch/x86/kernel/Makefile           |  2 ++
 arch/x86/kernel/head64.c           |  8 ++++++
 arch/x86/kernel/tdx.c              | 40 ++++++++++++++++++++++++++++++
 5 files changed, 73 insertions(+)
 create mode 100644 arch/x86/include/asm/tdx.h
 create mode 100644 arch/x86/kernel/tdx.c

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index d0ce5cfd3ac1..84997abeb401 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -238,6 +238,7 @@
 #define X86_FEATURE_VMW_VMMCALL		( 8*32+19) /* "" VMware prefers VMMCALL hypercall instruction */
 #define X86_FEATURE_PVUNLOCK		( 8*32+20) /* "" PV unlock function */
 #define X86_FEATURE_VCPUPREEMPT		( 8*32+21) /* "" PV vcpu_is_preempted function */
+#define X86_FEATURE_TDX_GUEST		( 8*32+22) /* Trusted Domain Extensions Guest */
 
 /* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
 #define X86_FEATURE_FSGSBASE		( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
new file mode 100644
index 000000000000..d552c7248bc7
--- /dev/null
+++ b/arch/x86/include/asm/tdx.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2020 Intel Corporation */
+#ifndef _ASM_X86_TDX_H
+#define _ASM_X86_TDX_H
+
+#include <linux/cpufeature.h>
+
+#define TDX_CPUID_LEAF_ID	0x21
+
+#ifdef CONFIG_INTEL_TDX_GUEST
+
+extern u64 is_tdx_guest;
+void __init tdx_early_init(void);
+
+#else
+
+#define is_tdx_guest		0ULL
+static inline void tdx_early_init(void) { };
+
+#endif /* CONFIG_INTEL_TDX_GUEST */
+
+#endif /* _ASM_X86_TDX_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index f91403a78594..159fccfece65 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -29,6 +29,7 @@ KASAN_SANITIZE_dumpstack_$(BITS).o			:= n
 KASAN_SANITIZE_stacktrace.o				:= n
 KASAN_SANITIZE_paravirt.o				:= n
 KASAN_SANITIZE_sev.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.
@@ -127,6 +128,7 @@ obj-$(CONFIG_PARAVIRT_CLOCK)	+= pvclock.o
 obj-$(CONFIG_X86_PMEM_LEGACY_DEVICE) += pmem.o
 
 obj-$(CONFIG_JAILHOUSE_GUEST)	+= jailhouse.o
+obj-$(CONFIG_INTEL_TDX_GUEST)	+= tdx.o
 
 obj-$(CONFIG_EISA)		+= eisa.o
 obj-$(CONFIG_PCSPKR_PLATFORM)	+= pcspeaker.o
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index f98c76a1d16c..97ce0d037387 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -40,6 +40,7 @@
 #include <asm/extable.h>
 #include <asm/trapnr.h>
 #include <asm/sev.h>
+#include <asm/tdx.h>
 
 /*
  * Manage page tables very early on.
@@ -495,6 +496,13 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
 
 	copy_bootdata(__va(real_mode_data));
 
+	/*
+	 * tdx_early_init() has dependency on command line parameters.
+	 * So the order of calling it should be after copy_bootdata()
+	 * (in which command line parameter is initialized).
+	 */
+	tdx_early_init();
+
 	/*
 	 * Load microcode early on BSP.
 	 */
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
new file mode 100644
index 000000000000..ad3ff5925153
--- /dev/null
+++ b/arch/x86/kernel/tdx.c
@@ -0,0 +1,40 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2020 Intel Corporation */
+
+#undef pr_fmt
+#define pr_fmt(fmt)     "tdx: " fmt
+
+#include <asm/tdx.h>
+
+/*
+ * Allocate it in the data region to avoid zeroing it during
+ * BSS initialization. It is mainly used in cc_platform_has()
+ * call during early boot call.
+ */
+u64 __section(".data") is_tdx_guest = 0;
+
+static void __init is_tdx_guest_init(void)
+{
+	u32 eax, sig[3];
+
+	if (cpuid_eax(0) < TDX_CPUID_LEAF_ID) {
+		is_tdx_guest = 0;
+		return;
+	}
+
+	cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2], &sig[1]);
+
+	is_tdx_guest = !memcmp("IntelTDX    ", sig, 12);
+}
+
+void __init tdx_early_init(void)
+{
+	is_tdx_guest_init();
+
+	if (!is_tdx_guest)
+		return;
+
+	setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
+
+	pr_info("Guest initialized\n");
+}
-- 
2.25.1

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