[RFC PATCH 03/15] x86/acrn: Add hypercall for ACRN guest

[Zhao Yakui]

When ACRN hypervisor is detected, the hypercall is needed so that the
ACRN guest can query/config some settings. For example: it can be used
to query the resources in hypervisor and manage the CPU/memory/device/
interrupt for guest operating system.

On x86 it is implemented with the VMCALL instruction.

Co-developed-by: Jason Chen CJ <jason.cj.chen@xxxxxxxxx>
Signed-off-by: Jason Chen CJ <jason.cj.chen@xxxxxxxxx>
Signed-off-by: Zhao Yakui <yakui.zhao@xxxxxxxxx>
---
 arch/x86/include/asm/acrn.h | 54 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/arch/x86/include/asm/acrn.h b/arch/x86/include/asm/acrn.h
index 857e6244..ab97c3d 100644
--- a/arch/x86/include/asm/acrn.h
+++ b/arch/x86/include/asm/acrn.h
@@ -11,4 +11,58 @@ extern void acrn_hv_vector_handler(struct pt_regs *regs);
 
 extern void acrn_setup_intr_irq(void (*handler)(void));
 extern void acrn_remove_intr_irq(void);
+
+/*
+ * Hypercalls for ACRN guest
+ *
+ * Hypercall number is passed in R8 register.
+ * Up to 2 arguments are passed in RDI, RSI.
+ * Return value will be placed in RAX.
+ */
+static inline long acrn_hypercall0(unsigned long hcall_id)
+{
+	long result;
+
+	/* the hypercall is implemented with the VMCALL instruction.
+	 * volatile qualifier is added to avoid that it is dropped
+	 * because of compiler optimization.
+	 */
+	asm volatile("movq %[hcall_id], %%r8\n\t"
+		     "vmcall\n\t"
+		     : "=a" (result)
+		     : [hcall_id] "g" (hcall_id)
+		     : "r8");
+
+	return result;
+}
+
+static inline long acrn_hypercall1(unsigned long hcall_id,
+				   unsigned long param1)
+{
+	long result;
+
+	asm volatile("movq %[hcall_id], %%r8\n\t"
+		     "vmcall\n\t"
+		     : "=a" (result)
+		     : [hcall_id] "g" (hcall_id), "D" (param1)
+		     : "r8");
+
+	return result;
+}
+
+static inline long acrn_hypercall2(unsigned long hcall_id,
+				   unsigned long param1,
+				   unsigned long param2)
+{
+	long result;
+
+	asm volatile("movq %[hcall_id], %%r8\n\t"
+		     "vmcall\n\t"
+		     : "=a" (result)
+		     : [hcall_id] "g" (hcall_id), "D" (param1), "S" (param2)
+		     : "r8");
+
+	return result;
+}
+
 #endif /* _ASM_X86_ACRN_H */
-- 
2.7.4