[PATCH 2/3] target/riscv: Support discontinuous PMU counters

[Rob Bradford]

There is no requirement that the enabled counters in the platform are
continuously numbered. Add a "pmu-mask" property that, if specified, can
be used to specify the enabled PMUs. In order to avoid ambiguity if
"pmu-mask" is specified then "pmu-num" must also match the number of
bits set in the mask.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
---
 target/riscv/cpu.c     |  1 +
 target/riscv/cpu_cfg.h |  1 +
 target/riscv/pmu.c     | 15 +++++++++++++--
 3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 9d79c20c1a..b89b006a76 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1817,6 +1817,7 @@ static void riscv_cpu_add_misa_properties(Object *cpu_obj)
 static Property riscv_cpu_extensions[] = {
     /* Defaults for standard extensions */
     DEFINE_PROP_UINT8("pmu-num", RISCVCPU, cfg.pmu_num, 16),
+    DEFINE_PROP_UINT32("pmu-mask", RISCVCPU, cfg.pmu_mask, 0),
     DEFINE_PROP_BOOL("sscofpmf", RISCVCPU, cfg.ext_sscofpmf, false),
     DEFINE_PROP_BOOL("Zifencei", RISCVCPU, cfg.ext_ifencei, true),
     DEFINE_PROP_BOOL("Zicsr", RISCVCPU, cfg.ext_icsr, true),
diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
index 0e6a0f245c..40f7d970bc 100644
--- a/target/riscv/cpu_cfg.h
+++ b/target/riscv/cpu_cfg.h
@@ -124,6 +124,7 @@ struct RISCVCPUConfig {
     bool ext_XVentanaCondOps;
 
     uint8_t pmu_num;
+    uint32_t pmu_mask;
     char *priv_spec;
     char *user_spec;
     char *bext_spec;
diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
index 13801ccb78..f97e25a1f6 100644
--- a/target/riscv/pmu.c
+++ b/target/riscv/pmu.c
@@ -437,6 +437,13 @@ int riscv_pmu_setup_timer(CPURISCVState *env, uint64_t 
value, uint32_t ctr_idx)
 void riscv_pmu_init(RISCVCPU *cpu, Error **errp)
 {
     uint8_t pmu_num = cpu->cfg.pmu_num;
+    uint32_t pmu_mask = cpu->cfg.pmu_mask;
+
+    if (pmu_mask && ctpop32(pmu_mask) != pmu_num) {
+        error_setg(errp, "Mismatch between number of enabled counters in "
+                         "\"pmu-mask\" and \"pmu-num\"");
+        return;
+    }
 
     if (pmu_num > (RV_MAX_MHPMCOUNTERS - 3)) {
         error_setg(errp, "Number of counters exceeds maximum available");
@@ -449,6 +456,10 @@ void riscv_pmu_init(RISCVCPU *cpu, Error **errp)
         return;
     }
 
-    /* Create a bitmask of available programmable counters */
-    cpu->pmu_avail_ctrs = MAKE_32BIT_MASK(3, pmu_num);
+    /* Create a bitmask of available programmable counters if none supplied */
+    if (pmu_mask) {
+        cpu->pmu_avail_ctrs = pmu_mask;
+    } else {
+        cpu->pmu_avail_ctrs = MAKE_32BIT_MASK(3, pmu_num);
+    }
 }
-- 
2.41.0