[PATCH v2 1/2] xen/arm: smccc: add support for SMCCCv1.2 extended input/output registers

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

SMCCC v1.2 AArch64 allows x0-x17 to be used as both parameter registers
and result registers for the SMC and HVC instructions.

Arm Firmware Framework for Armv8-A specification makes use of x0-x7 as
parameter and result registers.

Let us add new interface to support this extended set of input/output
registers.

This is based on 3fdc0cb59d97 ("arm64: smccc: Add support for SMCCCv1.2
extended input/output registers") by Sudeep Holla from the Linux kernel

Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
---
 xen/arch/arm/arm64/smc.S         | 43 ++++++++++++++++++++++++++++++++
 xen/arch/arm/include/asm/smccc.h | 42 +++++++++++++++++++++++++++++++
 xen/arch/arm/vsmc.c              |  2 +-
 3 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/arm64/smc.S b/xen/arch/arm/arm64/smc.S
index 91bae62dd4d2..1570bc8eb9d4 100644
--- a/xen/arch/arm/arm64/smc.S
+++ b/xen/arch/arm/arm64/smc.S
@@ -27,3 +27,46 @@ ENTRY(__arm_smccc_1_0_smc)
         stp     x2, x3, [x4, #SMCCC_RES_a2]
 1:
         ret
+
+
+/*
+ * void arm_smccc_1_2_smc(const struct arm_smccc_1_2_regs *args,
+ *                        struct arm_smccc_1_2_regs *res)
+ */
+ENTRY(arm_smccc_1_2_smc)
+    /* Save `res` and free a GPR that won't be clobbered */
+    stp     x1, x19, [sp, #-16]!
+
+    /* Ensure `args` won't be clobbered while loading regs in next step */
+    mov        x19, x0
+
+    /* Load the registers x0 - x17 from the struct arm_smccc_1_2_regs */
+    ldp        x0, x1, [x19, #0]
+    ldp        x2, x3, [x19, #16]
+    ldp        x4, x5, [x19, #32]
+    ldp        x6, x7, [x19, #48]
+    ldp        x8, x9, [x19, #64]
+    ldp        x10, x11, [x19, #80]
+    ldp        x12, x13, [x19, #96]
+    ldp        x14, x15, [x19, #112]
+    ldp        x16, x17, [x19, #128]
+
+    smc #0
+
+    /* Load the `res` from the stack */
+    ldr        x19, [sp]
+
+    /* Store the registers x0 - x17 into the result structure */
+    stp        x0, x1, [x19, #0]
+    stp        x2, x3, [x19, #16]
+    stp        x4, x5, [x19, #32]
+    stp        x6, x7, [x19, #48]
+    stp        x8, x9, [x19, #64]
+    stp        x10, x11, [x19, #80]
+    stp        x12, x13, [x19, #96]
+    stp        x14, x15, [x19, #112]
+    stp        x16, x17, [x19, #128]
+
+    /* Restore original x19 */
+    ldp     xzr, x19, [sp], #16
+    ret
diff --git a/xen/arch/arm/include/asm/smccc.h b/xen/arch/arm/include/asm/smccc.h
index b3dbeecc90ad..316adf968e74 100644
--- a/xen/arch/arm/include/asm/smccc.h
+++ b/xen/arch/arm/include/asm/smccc.h
@@ -33,6 +33,7 @@
 
 #define ARM_SMCCC_VERSION_1_0   SMCCC_VERSION(1, 0)
 #define ARM_SMCCC_VERSION_1_1   SMCCC_VERSION(1, 1)
+#define ARM_SMCCC_VERSION_1_2   SMCCC_VERSION(1, 2)
 
 /*
  * This file provides common defines for ARM SMC Calling Convention as
@@ -217,6 +218,7 @@ struct arm_smccc_res {
 #ifdef CONFIG_ARM_32
 #define arm_smccc_1_0_smc(...) arm_smccc_1_1_smc(__VA_ARGS__)
 #define arm_smccc_smc(...) arm_smccc_1_1_smc(__VA_ARGS__)
+
 #else
 
 void __arm_smccc_1_0_smc(register_t a0, register_t a1, register_t a2,
@@ -265,8 +267,48 @@ void __arm_smccc_1_0_smc(register_t a0, register_t a1, 
register_t a2,
         else                                                    \
             arm_smccc_1_0_smc(__VA_ARGS__);                     \
     } while ( 0 )
+
+/**
+ * struct arm_smccc_1_2_regs - Arguments for or Results from SMC call
+ * @a0-a17 argument values from registers 0 to 17
+ */
+struct arm_smccc_1_2_regs {
+    unsigned long a0;
+    unsigned long a1;
+    unsigned long a2;
+    unsigned long a3;
+    unsigned long a4;
+    unsigned long a5;
+    unsigned long a6;
+    unsigned long a7;
+    unsigned long a8;
+    unsigned long a9;
+    unsigned long a10;
+    unsigned long a11;
+    unsigned long a12;
+    unsigned long a13;
+    unsigned long a14;
+    unsigned long a15;
+    unsigned long a16;
+    unsigned long a17;
+};
 #endif /* CONFIG_ARM_64 */
 
+/**
+ * arm_smccc_1_2_smc() - make SMC calls
+ * @args: arguments passed via struct arm_smccc_1_2_regs
+ * @res: result values via struct arm_smccc_1_2_regs
+ *
+ * This function is used to make SMC calls following SMC Calling Convention
+ * v1.2 or above. The content of the supplied param are copied from the
+ * structure to registers prior to the SMC instruction. The return values
+ * are updated with the content from registers on return from the SMC
+ * instruction.
+ */
+void arm_smccc_1_2_smc(const struct arm_smccc_1_2_regs *args,
+                       struct arm_smccc_1_2_regs *res);
+
+
 #endif /* __ASSEMBLY__ */
 
 /*
diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
index 676740ef1520..6f90c08a6304 100644
--- a/xen/arch/arm/vsmc.c
+++ b/xen/arch/arm/vsmc.c
@@ -93,7 +93,7 @@ static bool handle_arch(struct cpu_user_regs *regs)
     switch ( fid )
     {
     case ARM_SMCCC_VERSION_FID:
-        set_user_reg(regs, 0, ARM_SMCCC_VERSION_1_1);
+        set_user_reg(regs, 0, ARM_SMCCC_VERSION_1_2);
         return true;
 
     case ARM_SMCCC_ARCH_FEATURES_FID:
-- 
2.31.1