[PATCH v2 10/15] xen/arm: smccc: Implement SMCCC v1.1 inline primitive

[Julien Grall <julien.grall@arm.com>]

One of the major improvement of SMCCC v1.1 is that it only clobbers the
first 4 registers, both on 32 and 64bit. This means that it becomes very
easy to provide an inline version of the SMC call primitive, and avoid
performing a function call to stash the registers that woudl otherwise
be clobbered by SMCCC v1.0.

This patch has been adapted to Xen from Linux commit f2d3b2e8759a. The
changes mades are:
    - Using Xen coding style
    - Remove HVC as not used by Xen
    - Add arm_smccc_res structure

 Reviewed-by: Robin Murphy <robin.murphy@arm.com>
 Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
 Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
 Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Signed-off-by: Julien Grall <julien.grall@arm.com>

---

    Note that the patch is in arm64/for-next/core and should be merged
    in master soon.

    Changes in v2:
        - Patch added
---
 xen/include/asm-arm/smccc.h | 119 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)

diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h
index bc067892c7..154772b728 100644
--- a/xen/include/asm-arm/smccc.h
+++ b/xen/include/asm-arm/smccc.h
@@ -78,6 +78,125 @@ static inline uint32_t smccc_get_owner(register_t funcid)
     return (funcid >> ARM_SMCCC_OWNER_SHIFT) & ARM_SMCCC_OWNER_MASK;
 }
 
+/*
+ * struct arm_smccc_res - Result from SMC call
+ * @a0 - @a3 result values from registers 0 to 3
+ */
+struct arm_smccc_res {
+    unsigned long a0;
+    unsigned long a1;
+    unsigned long a2;
+    unsigned long a3;
+};
+
+/* SMCCC v1.1 implementation madness follows */
+#define ___count_args(_0, _1, _2, _3, _4, _5, _6, _7, _8, x, ...) x
+
+#define __count_args(...)                               \
+    ___count_args(__VA_ARGS__, 7, 6, 5, 4, 3, 2, 1, 0)
+
+#define __constraint_write_0                        \
+    "+r" (r0), "=&r" (r1), "=&r" (r2), "=&r" (r3)
+#define __constraint_write_1                        \
+    "+r" (r0), "+r" (r1), "=&r" (r2), "=&r" (r3)
+#define __constraint_write_2                        \
+    "+r" (r0), "+r" (r1), "+r" (r2), "=&r" (r3)
+#define __constraint_write_3                        \
+    "+r" (r0), "+r" (r1), "+r" (r2), "+r" (r3)
+#define __constraint_write_4    __constraint_write_3
+#define __constraint_write_5    __constraint_write_4
+#define __constraint_write_6    __constraint_write_5
+#define __constraint_write_7    __constraint_write_6
+
+#define __constraint_read_0
+#define __constraint_read_1
+#define __constraint_read_2
+#define __constraint_read_3
+#define __constraint_read_4 "r" (r4)
+#define __constraint_read_5 __constraint_read_4, "r" (r5)
+#define __constraint_read_6 __constraint_read_5, "r" (r6)
+#define __constraint_read_7 __constraint_read_6, "r" (r7)
+
+#define __declare_arg_0(a0, res)                        \
+    struct arm_smccc_res    *___res = res;              \
+    register uin32_t        r0 asm("r0") = a0;          \
+    register unsigned long  r1 asm("r1");               \
+    register unsigned long  r2 asm("r2");               \
+    register unsigned long  r3 asm("r3")
+
+#define __declare_arg_1(a0, a1, res)                    \
+    struct arm_smccc_res    *___res = res;              \
+    register uint32_t       r0 asm("r0") = a0;          \
+    register typeof(a1)     r1 asm("r1") = a1;          \
+    register unsigned long  r2 asm("r2");               \
+    register unsigned long  r3 asm("r3")
+
+#define __declare_arg_2(a0, a1, a2, res)                \
+    struct arm_smccc_res    *___res = res;				\
+    register u32            r0 asm("r0") = a0;          \
+    register typeof(a1)     r1 asm("r1") = a1;          \
+    register typeof(a2)     r2 asm("r2") = a2;          \
+    register unsigned long  r3 asm("r3")
+
+#define __declare_arg_3(a0, a1, a2, a3, res)            \
+    struct arm_smccc_res    *___res = res;              \
+    register u32            r0 asm("r0") = a0;          \
+    register typeof(a1)     r1 asm("r1") = a1;          \
+    register typeof(a2)     r2 asm("r2") = a2;          \
+    register typeof(a3)     r3 asm("r3") = a3
+
+#define __declare_arg_4(a0, a1, a2, a3, a4, res)        \
+    __declare_arg_3(a0, a1, a2, a3, res);               \
+    register typeof(a4) r4 asm("r4") = a4
+
+#define __declare_arg_5(a0, a1, a2, a3, a4, a5, res)    \
+    __declare_arg_4(a0, a1, a2, a3, a4, res);           \
+    register typeof(a5) r5 asm("r5") = a5
+
+#define __declare_arg_6(a0, a1, a2, a3, a4, a5, a6, res)    \
+    __declare_arg_5(a0, a1, a2, a3, a4, a5, res);           \
+    register typeof(a6) r6 asm("r6") = a6
+
+#define __declare_arg_7(a0, a1, a2, a3, a4, a5, a6, a7, res)    \
+    __declare_arg_6(a0, a1, a2, a3, a4, a5, a6, res);           \
+    register typeof(a7) r7 asm("r7") = a7
+
+#define ___declare_args(count, ...) __declare_arg_ ## count(__VA_ARGS__)
+#define __declare_args(count, ...)  ___declare_args(count, __VA_ARGS__)
+
+#define ___constraints(count)                       \
+    : __constraint_write_ ## count                  \
+    : __constraint_read_ ## count                   \
+    : "memory"
+#define __constraints(count)    ___constraints(count)
+
+/*
+ * arm_smccc_1_1_smc() - make an SMCCC v1.1 compliant SMC call
+ *
+ * This is a variadic macro taking one to eight source arguments, and
+ * an optional return structure.
+ *
+ * @a0-a7: arguments passed in registers 0 to 7
+ * @res: result values from registers 0 to 3
+ *
+ * This macro is used to make SMC calls following SMC Calling Convention v1.1.
+ * The content of the supplied param are copied to registers 0 to 7 prior
+ * to the SMC instruction. The return values are updated with the content
+ * from register 0 to 3 on return from the SMC instruction if not NULL.
+ *
+ * We have an output list that is not necessarily used, and GCC feels
+ * entitled to optimise the whole sequence away. "volatile" is what
+ * makes it stick.
+ */
+#define arm_smccc_1_1_smc(...)                                  \
+    do {                                                        \
+        __declare_args(__count_args(__VA_ARGS__), __VA_ARGS__); \
+        asm volatile("smc #0\n"                                 \
+                     __constraints(__count_args(__VA_ARGS__))); \
+        if ( ___res )                                           \
+        *___res = (typeof(*___res)){r0, r1, r2, r3};            \
+    } while ( 0 )
+
 #endif
 
 /*
-- 
2.11.0


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