RISC-V: Add SBI PMU snapshot definitions

SBI PMU Snapshot function optimizes the number of traps to
higher privilege mode by leveraging a shared memory between the S/VS-mode
and the M/HS mode. Add the definitions for that extension and new error
codes.
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20240420151741.962500-6-atishp@rivosinc.comSigned-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/include/asm/sbi.h

@@ -132,6 +132,7 @@ enum sbi_ext_pmu_fid {
 	SBI_EXT_PMU_COUNTER_STOP,
 	SBI_EXT_PMU_COUNTER_FW_READ,
 	SBI_EXT_PMU_COUNTER_FW_READ_HI,
+	SBI_EXT_PMU_SNAPSHOT_SET_SHMEM,
 };
 
 union sbi_pmu_ctr_info {
@@ -148,6 +149,13 @@ union sbi_pmu_ctr_info {
 	};
 };
 
+/* Data structure to contain the pmu snapshot data */
+struct riscv_pmu_snapshot_data {
+	u64 ctr_overflow_mask;
+	u64 ctr_values[64];
+	u64 reserved[447];
+};
+
 #define RISCV_PMU_RAW_EVENT_MASK GENMASK_ULL(47, 0)
 #define RISCV_PMU_RAW_EVENT_IDX 0x20000
 
@@ -244,9 +252,11 @@ enum sbi_pmu_ctr_type {
 
 /* Flags defined for counter start function */
 #define SBI_PMU_START_FLAG_SET_INIT_VALUE BIT(0)
+#define SBI_PMU_START_FLAG_INIT_SNAPSHOT BIT(1)
 
 /* Flags defined for counter stop function */
 #define SBI_PMU_STOP_FLAG_RESET BIT(0)
+#define SBI_PMU_STOP_FLAG_TAKE_SNAPSHOT BIT(1)
 
 enum sbi_ext_dbcn_fid {
 	SBI_EXT_DBCN_CONSOLE_WRITE = 0,
@@ -285,6 +295,7 @@ struct sbi_sta_struct {
 #define SBI_ERR_ALREADY_AVAILABLE -6
 #define SBI_ERR_ALREADY_STARTED -7
 #define SBI_ERR_ALREADY_STOPPED -8
+#define SBI_ERR_NO_SHMEM	-9
 
 extern unsigned long sbi_spec_version;
 struct sbiret {