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Re: [Xen-devel] [PATCH v2 09/15] xen/arm: psci: Detect SMCCC version



Julien,


On 08.02.18 21:21, Julien Grall wrote:
PSCI 1.0 and later allows the SMCCC version to be (indirectly) probed
via PSCI_FEATURES. If the PSCI_FEATURES does not exist (PSCI 0.2 or
earlier) and the function return an error, then we considered SMCCC 1.0
is implemented.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
     Changes in v2:
         - Patch added
---
  xen/arch/arm/psci.c         | 34 +++++++++++++++++++++++++++++++++-
  xen/include/asm-arm/smccc.h |  5 ++++-
  2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/psci.c b/xen/arch/arm/psci.c

I find it strange to determine SMCCC version in PSCI code. psci.c is not the first place, where I will look for SMCCC version discovery.

I think it is better to add smccc.c, where such functions can reside.

index 5dda35cd7c..bc7b2260e8 100644
--- a/xen/arch/arm/psci.c
+++ b/xen/arch/arm/psci.c
@@ -37,6 +37,7 @@
  #endif
uint32_t psci_ver;
+uint32_t smccc_ver;

And this variable actually is not related to PSCI.
static uint32_t psci_cpu_on_nr; @@ -57,6 +58,14 @@ void call_psci_system_reset(void)
          call_smc(PSCI_0_2_FN32_SYSTEM_RESET, 0, 0, 0);
  }
+static int __init psci_features(uint32_t psci_func_id)
+{
+    if ( psci_ver < PSCI_VERSION(1, 0) )
+        return PSCI_NOT_SUPPORTED;
+
+    return call_smc(PSCI_1_0_FN32_PSCI_FEATURES, psci_func_id, 0, 0);
+}
+
  int __init psci_is_smc_method(const struct dt_device_node *psci)
  {
      int ret;
@@ -82,6 +91,24 @@ int __init psci_is_smc_method(const struct dt_device_node 
*psci)
      return 0;
  }
+static void __init psci_init_smccc(void)
+{
+    /* PSCI is using at least SMCC 1.0 calling convention. */
+    smccc_ver = ARM_SMCCC_VERSION_1_0;
+
+    if ( psci_features(ARM_SMCCC_VERSION_FID) != PSCI_NOT_SUPPORTED )
+    {
+        uint32_t ret;
+
+        ret = call_smc(ARM_SMCCC_VERSION_FID, 0, 0, 0);
+        if ( ret != ARM_SMCCC_NOT_SUPPORTED )
+            smccc_ver = ret;
+    }
+
+    printk(XENLOG_INFO "Using SMC Calling Convention v%u.%u\n",
+           SMCCC_VERSION_MAJOR(smccc_ver), SMCCC_VERSION_MINOR(smccc_ver));
+}
+
  int __init psci_init_0_1(void)
  {
      int ret;
@@ -173,7 +200,12 @@ int __init psci_init(void)
      if ( ret )
          ret = psci_init_0_1();
- return ret;
+    if ( ret )
+        return ret;
+
+    psci_init_smccc();
+
+    return 0;
  }
/*
diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h
index caa2c9cc1b..bc067892c7 100644
--- a/xen/include/asm-arm/smccc.h
+++ b/xen/include/asm-arm/smccc.h
@@ -52,6 +52,8 @@
#ifndef __ASSEMBLY__ +extern uint32_t smccc_ver;
+
  /* Check if this is fast call. */
  static inline bool smccc_is_fast_call(register_t funcid)
  {
@@ -137,8 +139,9 @@ static inline uint32_t smccc_get_owner(register_t funcid)
                        ARM_SMCCC_OWNER_ARCH,         \
                        0x8000)
-/* Only one error code defined in SMCCC */
+/* SMCCC error codes */
  #define ARM_SMCCC_ERR_UNKNOWN_FUNCTION  (-1)
+#define ARM_SMCCC_NOT_SUPPORTED         (-1)

In patch "xen/arm: vsmc: Implement SMCCC 1.1" you return plain -1 in static bool handle_arch(struct cpu_user_regs *regs)

Could you please move definition of ARM_SMCCC_NOT_SUPPORTED into that patch and use it in mentioned function or add new patch that changes -1 to ARM_SMCCC_NOT_SUPPORTED ?

/* SMCCC function identifier range which is reserved for existing APIs */
  #define ARM_SMCCC_RESERVED_RANGE_START  0x0


--
Volodymyr Babchuk

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