[PATCH v2 4/8] xen/arm: vsmc: Enable handling SiP-owned SCMI SMC calls

["Andrei Cherechesu (OSS)" <andrei.cherechesu@xxxxxxxxxxx>]

From: Andrei Cherechesu <andrei.cherechesu@xxxxxxx>

Change the handling of SiP SMC calls to be more generic,
instead of directly relying on the `platform_smc()` callback
implementation.

Try to handle the SiP SMC first through the `platform_smc()`
callback (if implemented). If not handled, check if the
SCMI layer is available and that the SMC is a valid SCMI
message. Handle it then within the SCMI layer which forwards
it to EL3 FW, only if the SMC comes from Dom0.

Signed-off-by: Andrei Cherechesu <andrei.cherechesu@xxxxxxx>
---
 xen/arch/arm/vsmc.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
index 7f2f5eb9ce..0de194a132 100644
--- a/xen/arch/arm/vsmc.c
+++ b/xen/arch/arm/vsmc.c
@@ -14,6 +14,7 @@
 #include <asm/cpufeature.h>
 #include <asm/monitor.h>
 #include <asm/regs.h>
+#include <asm/scmi-smc.h>
 #include <asm/smccc.h>
 #include <asm/tee/ffa.h>
 #include <asm/tee/tee.h>
@@ -224,6 +225,22 @@ static bool handle_sssc(struct cpu_user_regs *regs)
     }
 }
 
+/* Secure Calls defined by the Silicon Provider (SiP) */
+static bool handle_sip(struct cpu_user_regs *regs)
+{
+    uint32_t fid = (uint32_t)get_user_reg(regs, 0);
+
+    /* Firstly, let each platform define custom handling for these SMCs */
+    if ( platform_smc(regs) )
+        return true;
+
+    /* Otherwise, if valid SCMI SMC, forward the call to EL3 */
+    if ( scmi_is_enabled() && scmi_is_valid_smc_id(fid) )
+        return scmi_handle_smc(regs);
+
+    return false;
+}
+
 /*
  * vsmccc_handle_call() - handle SMC/HVC call according to ARM SMCCC.
  * returns true if that was valid SMCCC call (even if function number
@@ -288,7 +305,7 @@ static bool vsmccc_handle_call(struct cpu_user_regs *regs)
             handled = handle_sssc(regs);
             break;
         case ARM_SMCCC_OWNER_SIP:
-            handled = platform_smc(regs);
+            handled = handle_sip(regs);
             break;
         case ARM_SMCCC_OWNER_TRUSTED_APP ... ARM_SMCCC_OWNER_TRUSTED_APP_END:
         case ARM_SMCCC_OWNER_TRUSTED_OS ... ARM_SMCCC_OWNER_TRUSTED_OS_END:
-- 
2.45.2