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From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@intel.com>
Cc:     Tony Luck <tony.luck@intel.com>, Andi Kleen <ak@linux.intel.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Raj Ashok <ashok.raj@intel.com>,
        Sean Christopherson <seanjc@google.com>,
        linux-kernel@vger.kernel.org,
        Isaku Yamahata <isaku.yamahata@intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
Subject: [RFC v2-fix 1/1] x86/tdx: Wire up KVM hypercalls
Date:   Mon, 17 May 2021 17:15:51 -0700
Message-Id: <20210518001551.258126-1-sathyanarayanan.kuppuswamy@linux.intel.com>
In-Reply-To: <2a4e9702-5407-aa95-be9b-864775bbaabd@intel.com>
References: <2a4e9702-5407-aa95-be9b-864775bbaabd@intel.com>
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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

KVM hypercalls use the "vmcall" or "vmmcall" instructions.
Although the ABI is similar, those instructions no longer
function for TDX guests. Make vendor specififc TDVMCALLs
instead of VMCALL.

[Isaku: proposed KVM VENDOR string]
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
Changes since RFC v2:
 * Introduced INTEL_TDX_GUEST_KVM config for TDX+KVM related changes.
 * Removed "C" include file.
 * Fixed commit log as per Dave's comments.

 arch/x86/Kconfig                |  6 +++++
 arch/x86/include/asm/kvm_para.h | 21 +++++++++++++++
 arch/x86/include/asm/tdx.h      | 41 ++++++++++++++++++++++++++++
 arch/x86/kernel/Makefile        |  1 +
 arch/x86/kernel/tdcall.S        | 20 ++++++++++++++
 arch/x86/kernel/tdx-kvm.c       | 48 +++++++++++++++++++++++++++++++++
 6 files changed, 137 insertions(+)
 create mode 100644 arch/x86/kernel/tdx-kvm.c

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 9e0e0ff76bab..768df1b98487 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -886,6 +886,12 @@ config INTEL_TDX_GUEST
 	  run in a CPU mode that protects the confidentiality of TD memory
 	  contents and the TD’s CPU state from other software, including VMM.
 
+config INTEL_TDX_GUEST_KVM
+	def_bool y
+	depends on KVM_GUEST && INTEL_TDX_GUEST
+	help
+	 This option enables KVM specific hypercalls in TDX guest.
+
 endif #HYPERVISOR_GUEST
 
 source "arch/x86/Kconfig.cpu"
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 338119852512..2fa85481520b 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -6,6 +6,7 @@
 #include <asm/alternative.h>
 #include <linux/interrupt.h>
 #include <uapi/asm/kvm_para.h>
+#include <asm/tdx.h>
 
 extern void kvmclock_init(void);
 
@@ -34,6 +35,10 @@ static inline bool kvm_check_and_clear_guest_paused(void)
 static inline long kvm_hypercall0(unsigned int nr)
 {
 	long ret;
+
+	if (is_tdx_guest())
+		return tdx_kvm_hypercall0(nr);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr)
@@ -44,6 +49,10 @@ static inline long kvm_hypercall0(unsigned int nr)
 static inline long kvm_hypercall1(unsigned int nr, unsigned long p1)
 {
 	long ret;
+
+	if (is_tdx_guest())
+		return tdx_kvm_hypercall1(nr, p1);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr), "b"(p1)
@@ -55,6 +64,10 @@ static inline long kvm_hypercall2(unsigned int nr, unsigned long p1,
 				  unsigned long p2)
 {
 	long ret;
+
+	if (is_tdx_guest())
+		return tdx_kvm_hypercall2(nr, p1, p2);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr), "b"(p1), "c"(p2)
@@ -66,6 +79,10 @@ static inline long kvm_hypercall3(unsigned int nr, unsigned long p1,
 				  unsigned long p2, unsigned long p3)
 {
 	long ret;
+
+	if (is_tdx_guest())
+		return tdx_kvm_hypercall3(nr, p1, p2, p3);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr), "b"(p1), "c"(p2), "d"(p3)
@@ -78,6 +95,10 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1,
 				  unsigned long p4)
 {
 	long ret;
+
+	if (is_tdx_guest())
+		return tdx_kvm_hypercall4(nr, p1, p2, p3, p4);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr), "b"(p1), "c"(p2), "d"(p3), "S"(p4)
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 8ab4067afefc..eb758b506dba 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -73,4 +73,45 @@ static inline void tdx_early_init(void) { };
 
 #endif /* CONFIG_INTEL_TDX_GUEST */
 
+#ifdef CONFIG_INTEL_TDX_GUEST_KVM
+u64 __tdx_hypercall_vendor_kvm(u64 fn, u64 r12, u64 r13, u64 r14,
+			       u64 r15, struct tdx_hypercall_output *out);
+long tdx_kvm_hypercall0(unsigned int nr);
+long tdx_kvm_hypercall1(unsigned int nr, unsigned long p1);
+long tdx_kvm_hypercall2(unsigned int nr, unsigned long p1, unsigned long p2);
+long tdx_kvm_hypercall3(unsigned int nr, unsigned long p1, unsigned long p2,
+		unsigned long p3);
+long tdx_kvm_hypercall4(unsigned int nr, unsigned long p1, unsigned long p2,
+		unsigned long p3, unsigned long p4);
+#else
+static inline long tdx_kvm_hypercall0(unsigned int nr)
+{
+	return -ENODEV;
+}
+
+static inline long tdx_kvm_hypercall1(unsigned int nr, unsigned long p1)
+{
+	return -ENODEV;
+}
+
+static inline long tdx_kvm_hypercall2(unsigned int nr, unsigned long p1,
+				      unsigned long p2)
+{
+	return -ENODEV;
+}
+
+static inline long tdx_kvm_hypercall3(unsigned int nr, unsigned long p1,
+				      unsigned long p2, unsigned long p3)
+{
+	return -ENODEV;
+}
+
+static inline long tdx_kvm_hypercall4(unsigned int nr, unsigned long p1,
+				      unsigned long p2, unsigned long p3,
+				      unsigned long p4)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_INTEL_TDX_GUEST_KVM */
+
 #endif /* _ASM_X86_TDX_H */
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 7966c10ea8d1..a90fec004844 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -128,6 +128,7 @@ obj-$(CONFIG_X86_PMEM_LEGACY_DEVICE) += pmem.o
 
 obj-$(CONFIG_JAILHOUSE_GUEST)	+= jailhouse.o
 obj-$(CONFIG_INTEL_TDX_GUEST)	+= tdcall.o tdx.o
+obj-$(CONFIG_INTEL_TDX_GUEST_KVM) += tdx-kvm.o
 
 obj-$(CONFIG_EISA)		+= eisa.o
 obj-$(CONFIG_PCSPKR_PLATFORM)	+= pcspeaker.o
diff --git a/arch/x86/kernel/tdcall.S b/arch/x86/kernel/tdcall.S
index a484c4aef6e6..3c57a1d67b79 100644
--- a/arch/x86/kernel/tdcall.S
+++ b/arch/x86/kernel/tdcall.S
@@ -25,6 +25,8 @@
 					  TDG_R12 | TDG_R13 | \
 					  TDG_R14 | TDG_R15 )
 
+#define TDVMCALL_VENDOR_KVM		0x4d564b2e584454 /* "TDX.KVM" */
+
 /*
  * TDX guests use the TDCALL instruction to make requests to the
  * TDX module and hypercalls to the VMM. It is supported in
@@ -213,3 +215,21 @@ SYM_FUNC_START(__tdx_hypercall)
 	call do_tdx_hypercall
 	retq
 SYM_FUNC_END(__tdx_hypercall)
+
+#ifdef CONFIG_INTEL_TDX_GUEST_KVM
+/*
+ * Helper function for KVM vendor TDVMCALLs. This assembly wrapper
+ * lets us reuse do_tdvmcall() for KVM-specific hypercalls (
+ * TDVMCALL_VENDOR_KVM).
+ */
+SYM_FUNC_START(__tdx_hypercall_vendor_kvm)
+	/*
+	 * R10 is not part of the function call ABI, but it is a part
+	 * of the TDVMCALL ABI. So set it before making call to the
+	 * do_tdx_hypercall().
+	 */
+	movq $TDVMCALL_VENDOR_KVM, %r10
+	call do_tdx_hypercall
+	retq
+SYM_FUNC_END(__tdx_hypercall_vendor_kvm)
+#endif /* CONFIG_INTEL_TDX_GUEST_KVM */
diff --git a/arch/x86/kernel/tdx-kvm.c b/arch/x86/kernel/tdx-kvm.c
new file mode 100644
index 000000000000..b21453a81e38
--- /dev/null
+++ b/arch/x86/kernel/tdx-kvm.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2020 Intel Corporation */
+
+#include <asm/tdx.h>
+
+static long tdx_kvm_hypercall(unsigned int fn, unsigned long r12,
+			      unsigned long r13, unsigned long r14,
+			      unsigned long r15)
+{
+	return __tdx_hypercall_vendor_kvm(fn, r12, r13, r14, r15, NULL);
+}
+
+/* Used by kvm_hypercall0() to trigger hypercall in TDX guest */
+long tdx_kvm_hypercall0(unsigned int nr)
+{
+	return tdx_kvm_hypercall(nr, 0, 0, 0, 0);
+}
+EXPORT_SYMBOL_GPL(tdx_kvm_hypercall0);
+
+/* Used by kvm_hypercall1() to trigger hypercall in TDX guest */
+long tdx_kvm_hypercall1(unsigned int nr, unsigned long p1)
+{
+	return tdx_kvm_hypercall(nr, p1, 0, 0, 0);
+}
+EXPORT_SYMBOL_GPL(tdx_kvm_hypercall1);
+
+/* Used by kvm_hypercall2() to trigger hypercall in TDX guest */
+long tdx_kvm_hypercall2(unsigned int nr, unsigned long p1, unsigned long p2)
+{
+	return tdx_kvm_hypercall(nr, p1, p2, 0, 0);
+}
+EXPORT_SYMBOL_GPL(tdx_kvm_hypercall2);
+
+/* Used by kvm_hypercall3() to trigger hypercall in TDX guest */
+long tdx_kvm_hypercall3(unsigned int nr, unsigned long p1, unsigned long p2,
+		unsigned long p3)
+{
+	return tdx_kvm_hypercall(nr, p1, p2, p3, 0);
+}
+EXPORT_SYMBOL_GPL(tdx_kvm_hypercall3);
+
+/* Used by kvm_hypercall4() to trigger hypercall in TDX guest */
+long tdx_kvm_hypercall4(unsigned int nr, unsigned long p1, unsigned long p2,
+		unsigned long p3, unsigned long p4)
+{
+	return tdx_kvm_hypercall(nr, p1, p2, p3, p4);
+}
+EXPORT_SYMBOL_GPL(tdx_kvm_hypercall4);
-- 
2.25.1