x86/acrn: Introduce hypercall interfaces

The Service VM communicates with the hypervisor via conventional
hypercalls. VMCALL instruction is used to make the hypercalls.

ACRN hypercall ABI:
  * Hypercall number is in R8 register.
  * Up to 2 parameters are in RDI and RSI registers.
  * Return value is in RAX register.

Introduce the ACRN hypercall interfaces. Because GCC doesn't support R8
register as direct register constraints, use supported constraint as
input with a explicit MOV to R8 in beginning of asm.

Cc: Dave Hansen <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Fengwei Yin <[email protected]>
Cc: Zhi Wang <[email protected]>
Cc: Zhenyu Wang <[email protected]>
Cc: Yu Wang <[email protected]>
Cc: Reinette Chatre <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Arvind Sankar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Segher Boessenkool <[email protected]>
Originally-by: Yakui Zhao <[email protected]>
Reviewed-by: Reinette Chatre <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Acked-by: Borislav Petkov <[email protected]>
Signed-off-by: Shuo Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: Shuo Liu

arch/x86/include/asm/acrn.h

@@ -21,4 +21,58 @@ static inline u32 acrn_cpuid_base(void)
 	return 0;
 }
 
+/*
+ * Hypercalls for ACRN
+ *
+ * - VMCALL instruction is used to implement ACRN hypercalls.
+ * - ACRN hypercall ABI:
+ *   - Hypercall number is passed in R8 register.
+ *   - Up to 2 arguments are passed in RDI, RSI.
+ *   - Return value will be placed in RAX.
+ *
+ * Because GCC doesn't support R8 register as direct register constraints, use
+ * supported constraint as input with a explicit MOV to R8 in beginning of asm.
+ */
+static inline long acrn_hypercall0(unsigned long hcall_id)
+{
+	long result;
+
+	asm volatile("movl %1, %%r8d\n\t"
+		     "vmcall\n\t"
+		     : "=a" (result)
+		     : "g" (hcall_id)
+		     : "r8", "memory");
+
+	return result;
+}
+
+static inline long acrn_hypercall1(unsigned long hcall_id,
+				   unsigned long param1)
+{
+	long result;
+
+	asm volatile("movl %1, %%r8d\n\t"
+		     "vmcall\n\t"
+		     : "=a" (result)
+		     : "g" (hcall_id), "D" (param1)
+		     : "r8", "memory");
+
+	return result;
+}
+
+static inline long acrn_hypercall2(unsigned long hcall_id,
+				   unsigned long param1,
+				   unsigned long param2)
+{
+	long result;
+
+	asm volatile("movl %1, %%r8d\n\t"
+		     "vmcall\n\t"
+		     : "=a" (result)
+		     : "g" (hcall_id), "D" (param1), "S" (param2)
+		     : "r8", "memory");
+
+	return result;
+}
+
 #endif /* _ASM_X86_ACRN_H */