Re: [PATCH v2 5/6] target/riscv: Add "pmu-mask" property to replace "pmu-num"

[LIU Zhiwei]

On 2023/10/12 20:38, Rob Bradford wrote:

On Thu, 2023-10-12 at 17:05 +0800, LIU Zhiwei wrote:

On 2023/10/11 22:45, Rob Bradford wrote:

Using a mask instead of the number of PMU devices supports the

accurate
emulation of platforms that have a discontinuous set of PMU
counters.

Generate a warning if the old property changed from the default but
still go ahead and use it to generate the mask if the user has
changed
it from the default

Signed-off-by: Rob Bradford <rbradf...@rivosinc.com>
---
  target/riscv/cpu.c     |  5 +++--
  target/riscv/cpu_cfg.h |  3 ++-
  target/riscv/machine.c |  2 +-
  target/riscv/pmu.c     | 14 ++++++++++----
  4 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index c9d8fc12fe..4d2987e568 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1487,7 +1487,7 @@ static void riscv_cpu_realize_tcg(DeviceState
*dev, Error **errp)
          riscv_timer_init(cpu);
      }

- if (cpu->cfg.pmu_num) {

+    if (cpu->cfg.pmu_mask) {
          riscv_pmu_init(cpu, &local_err);
          if (local_err != NULL) {
              error_propagate(errp, local_err);
@@ -1812,7 +1812,8 @@ 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_UINT8("pmu-num", RISCVCPU, cfg.pmu_num, 16), /*
Deprecated */
+    DEFINE_PROP_UINT32("pmu-mask", RISCVCPU, cfg.pmu_mask,
MAKE_32BIT_MASK(3, 16)),
      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..d273487040 100644
--- a/target/riscv/cpu_cfg.h
+++ b/target/riscv/cpu_cfg.h
@@ -123,7 +123,8 @@ struct RISCVCPUConfig {
      bool ext_xtheadsync;
      bool ext_XVentanaCondOps;

- uint8_t pmu_num;

+    uint8_t pmu_num; /* Deprecated */
+    uint32_t pmu_mask;
      char *priv_spec;
      char *user_spec;
      char *bext_spec;
diff --git a/target/riscv/machine.c b/target/riscv/machine.c
index c7c862cdd3..9f6e3f7a6d 100644
--- a/target/riscv/machine.c
+++ b/target/riscv/machine.c
@@ -313,7 +313,7 @@ static bool pmu_needed(void *opaque)
  {
      RISCVCPU *cpu = opaque;

- return cpu->cfg.pmu_num;

+    return (cpu->cfg.pmu_mask > 0);
  }

 static const VMStateDescription vmstate_pmu_ctr_state = {

diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
index 360c76f63e..f2d35b4d3b 100644
--- a/target/riscv/pmu.c
+++ b/target/riscv/pmu.c
@@ -18,6 +18,7 @@

 #include "qemu/osdep.h"

  #include "qemu/log.h"
+#include "qemu/error-report.h"
  #include "cpu.h"
  #include "pmu.h"
  #include "sysemu/cpu-timers.h"
@@ -182,7 +183,7 @@ int riscv_pmu_incr_ctr(RISCVCPU *cpu, enum
riscv_pmu_event_idx event_idx)
      CPURISCVState *env = &cpu->env;
      gpointer value;

- if (!cpu->cfg.pmu_num) {

+    if (!cpu->cfg.pmu_mask) {
          return 0;
      }
      value = g_hash_table_lookup(cpu->pmu_event_ctr_map,
@@ -432,7 +433,7 @@ void riscv_pmu_init(RISCVCPU *cpu, Error
**errp)
  {
      uint8_t pmu_num = cpu->cfg.pmu_num;

- if (pmu_num > (RV_MAX_MHPMCOUNTERS - 3)) {

+    if (ctpop32(cpu->cfg.pmu_mask) > (RV_MAX_MHPMCOUNTERS - 3)) {

         error_setg(errp, "Number of counters exceeds maximum

available");
          return;
      }
@@ -443,6 +444,11 @@ 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);
+    /* Check if user set it by comparing against default */
+    if (pmu_num != 16) {
+        warn_report("\"pmu-num\" property is deprecated; use
\"pmu-mask\"");
+        cpu->cfg.pmu_mask = MAKE_32BIT_MASK(3, pmu_num);
+    }
+
+    cpu->pmu_avail_ctrs = cpu->cfg.pmu_mask;

How to process the pmu_mask[0:2] no-zero bits? They should not

included into pmu_avail_ctrs.

Good point, thanks Zhiwei. I think rather than masking those bits it is
better to add a check and error out if those bits are set.

Agree.

Thanks,
Zhiwei

Cheers,

Rob

Zhiwei

 }