[PATCH v5 1/6] arm64: rsi: Add RSI host call structure and helper function

[Kameron Carr <kameroncarr@linux.microsoft.com>]

Add struct rsi_host_call to arm-smccc-rsi.h, which represents the host
call data structure used by the Realm Management Monitor (RMM) for the
RSI_HOST_CALL interface. The structure contains a 16-bit immediate field
and 31 general-purpose register values, aligned to 256 bytes as required
by the CCA RMM specification.

Add rsi_host_call() static inline wrapper in arm-rsi-cmds.h that invokes
SMC_RSI_HOST_CALL with the physical address of the host call structure.
This will be used by Hyper-V guest code to route hypercalls through the
RSI interface when running inside an Arm CCA Realm.

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Signed-off-by: Kameron Carr <kameroncarr@linux.microsoft.com>
---
 include/linux/arm-rsi-cmds.h  | 22 ++++++++++++++++++++++
 include/linux/arm-smccc-rsi.h |  7 +++++++
 2 files changed, 29 insertions(+)

diff --git a/include/linux/arm-rsi-cmds.h b/include/linux/arm-rsi-cmds.h
index 3f7a6a8..01d292e 100644
--- a/include/linux/arm-rsi-cmds.h
+++ b/include/linux/arm-rsi-cmds.h
@@ -236,4 +236,26 @@ static inline unsigned long rsi_attestation_token_continue(phys_addr_t granule,
 	return res.a0;
 }
 
+/**
+ * rsi_host_call - Make a Host call.
+ * @host_call_struct: IPA of host call structure
+ *
+ * This call will fail if the IPA of the host call structure:
+ * * is not aligned to 256 bytes,
+ * * is not protected / encrypted,
+ * * is RIPAS_EMPTY
+ *
+ * Returns:
+ *  On success, returns RSI_SUCCESS.
+ *  Otherwise, returns an error code.
+ */
+static inline unsigned long rsi_host_call(phys_addr_t host_call_struct)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(SMC_RSI_HOST_CALL, host_call_struct, 0, 0, 0, 0, 0, 0,
+		      &res);
+	return res.a0;
+}
+
 #endif /* __LINUX_ARM_RSI_CMDS_H_ */
diff --git a/include/linux/arm-smccc-rsi.h b/include/linux/arm-smccc-rsi.h
index fddb779..4c8530b 100644
--- a/include/linux/arm-smccc-rsi.h
+++ b/include/linux/arm-smccc-rsi.h
@@ -142,6 +142,13 @@ struct realm_config {
 	 */
 } __aligned(0x1000);
 
+struct rsi_host_call {
+	u16 immediate;
+	u8 _padding[6];
+	u64 gprs[31];
+} __aligned(256);
+static_assert(sizeof(struct rsi_host_call) == 256);
+
 #endif /* __ASSEMBLER__ */
 
 /*
-- 
2.45.4