[PATCH v6 4/4] x86/acrn: Add hypercall for ACRN guest

[Zhao Yakui <yakui.zhao@intel.com>]

When the 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.

Add the hypercall so that the ACRN guest can communicate with the
low-level ACRN hypervisor. On x86 it is implemented with the VMCALL
instruction.

Co-developed-by: Jason Chen CJ <jason.cj.chen@intel.com>
Signed-off-by: Jason Chen CJ <jason.cj.chen@intel.com>
Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
---
V1->V2: Refine the comments for the function of acrn_hypercall0/1/2
v2->v3: Use the "vmcall" mnemonic to replace hard-code byte definition
v4->v5: Use _ASM_X86_ACRN_HYPERCALL_H instead of _ASM_X86_ACRNHYPERCALL_H.
        Use the "VMCALL" mnemonic in comment/commit log.
        Uppercase r8/rdi/rsi/rax for hypercall parameter register in comment.
v5->v6: Remove explicit local register variable for inline assembly
---
 arch/x86/include/asm/acrn_hypercall.h | 84 +++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 arch/x86/include/asm/acrn_hypercall.h

diff --git a/arch/x86/include/asm/acrn_hypercall.h b/arch/x86/include/asm/acrn_hypercall.h
new file mode 100644
index 0000000..5cb438e
--- /dev/null
+++ b/arch/x86/include/asm/acrn_hypercall.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_X86_ACRN_HYPERCALL_H
+#define _ASM_X86_ACRN_HYPERCALL_H
+
+#include <linux/errno.h>
+
+#ifdef CONFIG_ACRN_GUEST
+
+/*
+ * 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;
+}
+
+#else
+
+static inline long acrn_hypercall0(unsigned long hcall_id)
+{
+	return -ENOTSUPP;
+}
+
+static inline long acrn_hypercall1(unsigned long hcall_id,
+				   unsigned long param1)
+{
+	return -ENOTSUPP;
+}
+
+static inline long acrn_hypercall2(unsigned long hcall_id,
+				   unsigned long param1,
+				   unsigned long param2)
+{
+	return -ENOTSUPP;
+}
+#endif /* CONFIG_ACRN_GUEST */
+#endif /* _ASM_X86_ACRN_HYPERCALL_H */
-- 
2.7.4