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Subject[PATCHv5 19/30] x86/tdx: Wire up KVM hypercalls
Date
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@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-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@linux.intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/coco/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.c b/arch/x86/coco/tdx.c
index 391a05c7b1da..c82e8eda8c8b 100644
--- a/arch/x86/coco/tdx.c
+++ b/arch/x86/coco/tdx.c
@@ -58,6 +58,23 @@ 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
+
static inline void tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
struct tdx_module_output *out)
{
diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h
index 56935ebb1dfe..57bc74e112f2 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 c20062698198..db8bf9a86b97 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -75,5 +75,16 @@ 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 */
--
2.34.1
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