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Re: [Xen-devel] [PATCH v3 02/17] xen/arm: vsmc: Implement SMCCC 1.1



Hi Julien,

On 15.02.18 17:02, Julien Grall wrote:
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>


---
     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


--
Volodymyr Babchuk

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