[Xen-devel] [PATCH v5 03/18] xen/arm: vsmc: Implement SMCCC 1.1

[Julien Grall <julien.grall@xxxxxxx>]

The new SMC Calling Convention (v1.1) allows for a reduced overhead when
calling into the firmware, and provides a new feature discovery
mechanism. See "Firmware interfaces for mitigating CVE-2017-5715"
ARM DEN 00070A.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Volodymyr Babchuk <volodymyr.babchuk@xxxxxxxx>
Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---
    Changes in v4:
        - Add Volodymyr's reviewed-by
        - Add Stefano's acked-by

    Changes in v3:
        - Use ARM_SMCCC_NOT_SUPPORTED rather than hardcoded return

    Changes in v2:
        - Add a humand readable name for the specification
---
 xen/arch/arm/vpsci.c        |  1 +
 xen/arch/arm/vsmc.c         | 23 +++++++++++++++++++++++
 xen/include/asm-arm/smccc.h | 18 +++++++++++++++++-
 3 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/vpsci.c b/xen/arch/arm/vpsci.c
index e82b62db1a..19ee7caeb4 100644
--- a/xen/arch/arm/vpsci.c
+++ b/xen/arch/arm/vpsci.c
@@ -212,6 +212,7 @@ static int32_t do_psci_1_0_features(uint32_t psci_func_id)
     case PSCI_0_2_FN32_SYSTEM_OFF:
     case PSCI_0_2_FN32_SYSTEM_RESET:
     case PSCI_1_0_FN32_PSCI_FEATURES:
+    case ARM_SMCCC_VERSION_FID:
         return 0;
     default:
         return PSCI_NOT_SUPPORTED;
diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
index 3d3bd95fee..7ec492741b 100644
--- a/xen/arch/arm/vsmc.c
+++ b/xen/arch/arm/vsmc.c
@@ -81,6 +81,26 @@ static bool fill_function_call_count(struct cpu_user_regs 
*regs, uint32_t cnt)
     return true;
 }
 
+/* SMCCC interface for ARM Architecture */
+static bool handle_arch(struct cpu_user_regs *regs)
+{
+    uint32_t fid = (uint32_t)get_user_reg(regs, 0);
+
+    switch ( fid )
+    {
+    case ARM_SMCCC_VERSION_FID:
+        set_user_reg(regs, 0, ARM_SMCCC_VERSION_1_1);
+        return true;
+
+    case ARM_SMCCC_ARCH_FEATURES_FID:
+        /* Nothing supported yet */
+        set_user_reg(regs, 0, ARM_SMCCC_NOT_SUPPORTED);
+        return true;
+    }
+
+    return false;
+}
+
 /* SMCCC interface for hypervisor. Tell about itself. */
 static bool handle_hypervisor(struct cpu_user_regs *regs)
 {
@@ -188,6 +208,9 @@ static bool vsmccc_handle_call(struct cpu_user_regs *regs)
     {
         switch ( smccc_get_owner(funcid) )
         {
+        case ARM_SMCCC_OWNER_ARCH:
+            handled = handle_arch(regs);
+            break;
         case ARM_SMCCC_OWNER_HYPERVISOR:
             handled = handle_hypervisor(regs);
             break;
diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h
index 62b3a8cdf5..629cc5150b 100644
--- a/xen/include/asm-arm/smccc.h
+++ b/xen/include/asm-arm/smccc.h
@@ -16,6 +16,9 @@
 #ifndef __ASM_ARM_SMCCC_H__
 #define __ASM_ARM_SMCCC_H__
 
+#define ARM_SMCCC_VERSION_1_0   0x10000
+#define ARM_SMCCC_VERSION_1_1   0x10001
+
 /*
  * This file provides common defines for ARM SMC Calling Convention as
  * specified in
@@ -100,8 +103,21 @@ static inline uint32_t smccc_get_owner(register_t funcid)
                        ARM_SMCCC_OWNER_##owner,     \
                        0xFF03)
 
-/* Only one error code defined in SMCCC */
+#define ARM_SMCCC_VERSION_FID                       \
+    ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,         \
+                       ARM_SMCCC_CONV_32,           \
+                       ARM_SMCCC_OWNER_ARCH,        \
+                       0x0)                         \
+
+#define ARM_SMCCC_ARCH_FEATURES_FID                 \
+    ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,         \
+                       ARM_SMCCC_CONV_32,           \
+                       ARM_SMCCC_OWNER_ARCH,        \
+                       0x1)
+
+/* SMCCC error codes */
 #define ARM_SMCCC_ERR_UNKNOWN_FUNCTION  (-1)
+#define ARM_SMCCC_NOT_SUPPORTED         (-1)
 
 /* SMCCC function identifier range which is reserved for existing APIs */
 #define ARM_SMCCC_RESERVED_RANGE_START  0x0
-- 
2.11.0


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