[tip: x86/tdx] x86/tdx: Wire up KVM hypercalls

[tip-bot2 for Kuppuswamy Sathyanarayanan]

The following commit has been merged into the x86/tdx branch of tip:

Commit-ID:     cfb8ec7a31f234b4519c104f1cc9accbc8b393a9
Gitweb:        https://git.kernel.org/tip/cfb8ec7a31f234b4519c104f1cc9accbc8b393a9
Author:        Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
AuthorDate:    Wed, 06 Apr 2022 02:29:28 +03:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Thu, 07 Apr 2022 08:27:52 -07:00

x86/tdx: Wire up KVM hypercalls

KVM hypercalls use the VMCALL or VMMCALL instructions. Although the ABI
is similar, those instructions no longer function for TDX guests.

Make vendor-specific TDVMCALLs instead of VMCALL. This enables TDX
guests to run with KVM acting as the hypervisor.

Among other things, KVM hypercall is used to send IPIs.

Since the KVM driver can be built as a kernel module, export
tdx_kvm_hypercall() to make the symbols visible to kvm.ko.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20220405232939.73860-20-kirill.shutemov@xxxxxxxxxxxxxxx
---
 arch/x86/coco/tdx/tdx.c         | 17 +++++++++++++++++
 arch/x86/include/asm/kvm_para.h | 22 ++++++++++++++++++++++
 arch/x86/include/asm/tdx.h      | 11 +++++++++++
 3 files changed, 50 insertions(+)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index cc14b7c..f50f530 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -64,6 +64,23 @@ static u64 hcall_func(u64 exit_reason)
 	return exit_reason;
 }
 
+#ifdef CONFIG_KVM_GUEST
+long tdx_kvm_hypercall(unsigned int nr, unsigned long p1, unsigned long p2,
+		       unsigned long p3, unsigned long p4)
+{
+	struct tdx_hypercall_args args = {
+		.r10 = nr,
+		.r11 = p1,
+		.r12 = p2,
+		.r13 = p3,
+		.r14 = p4,
+	};
+
+	return __tdx_hypercall(&args, 0);
+}
+EXPORT_SYMBOL_GPL(tdx_kvm_hypercall);
+#endif
+
 /*
  * Used for TDX guests to make calls directly to the TD module.  This
  * should only be used for calls that have no legitimate reason to fail
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 56935eb..57bc74e 100644
--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -7,6 +7,8 @@
 #include <linux/interrupt.h>
 #include <uapi/asm/kvm_para.h>
 
+#include <asm/tdx.h>
+
 #ifdef CONFIG_KVM_GUEST
 bool kvm_check_and_clear_guest_paused(void);
 #else
@@ -32,6 +34,10 @@ static inline bool kvm_check_and_clear_guest_paused(void)
 static inline long kvm_hypercall0(unsigned int nr)
 {
 	long ret;
+
+	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
+		return tdx_kvm_hypercall(nr, 0, 0, 0, 0);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr)
@@ -42,6 +48,10 @@ static inline long kvm_hypercall0(unsigned int nr)
 static inline long kvm_hypercall1(unsigned int nr, unsigned long p1)
 {
 	long ret;
+
+	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
+		return tdx_kvm_hypercall(nr, p1, 0, 0, 0);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr), "b"(p1)
@@ -53,6 +63,10 @@ static inline long kvm_hypercall2(unsigned int nr, unsigned long p1,
 				  unsigned long p2)
 {
 	long ret;
+
+	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
+		return tdx_kvm_hypercall(nr, p1, p2, 0, 0);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr), "b"(p1), "c"(p2)
@@ -64,6 +78,10 @@ static inline long kvm_hypercall3(unsigned int nr, unsigned long p1,
 				  unsigned long p2, unsigned long p3)
 {
 	long ret;
+
+	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
+		return tdx_kvm_hypercall(nr, p1, p2, p3, 0);
+
 	asm volatile(KVM_HYPERCALL
 		     : "=a"(ret)
 		     : "a"(nr), "b"(p1), "c"(p2), "d"(p3)
@@ -76,6 +94,10 @@ static inline long kvm_hypercall4(unsigned int nr, unsigned long p1,
 				  unsigned long p4)
 {
 	long ret;
+
+	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
+		return tdx_kvm_hypercall(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 9ffd0d2..020c81a 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -76,5 +76,16 @@ static inline bool tdx_early_handle_ve(struct pt_regs *regs) { return false; }
 
 #endif /* CONFIG_INTEL_TDX_GUEST */
 
+#if defined(CONFIG_KVM_GUEST) && defined(CONFIG_INTEL_TDX_GUEST)
+long tdx_kvm_hypercall(unsigned int nr, unsigned long p1, unsigned long p2,
+		       unsigned long p3, unsigned long p4);
+#else
+static inline long tdx_kvm_hypercall(unsigned int nr, unsigned long p1,
+				     unsigned long p2, unsigned long p3,
+				     unsigned long p4)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_INTEL_TDX_GUEST && CONFIG_KVM_GUEST */
 #endif /* !__ASSEMBLY__ */
 #endif /* _ASM_X86_TDX_H */