| Message ID | 20230802124906.24197-1-rbradford@rivosinc.com |
|---|---|
| State | New |
| Headers | show |
| Series | target/riscv: Implement WARL behaviour for mcountinhibit/mcounteren | expand |
On Wed, Aug 2, 2023 at 5:50 AM Rob Bradford <rbradford@rivosinc.com> wrote: > > These are WARL fields - zero out the bits for unavailable counters and > special case the TM bit in mcountinhibit which is hardwired to zero. > This patch achieves this by modifying the value written so that any use > of the field will see the correctly masked bits. > > Tested by modifying OpenSBI to write max value to these CSRs and upon > subsequent read the appropriate number of bits for number of PMUs is > enabled and the TM bit is zero in mcountinhibit. > > Signed-off-by: Rob Bradford <rbradford@rivosinc.com> > --- > target/riscv/csr.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/target/riscv/csr.c b/target/riscv/csr.c > index ea7585329e..495ff6a9c2 100644 > --- a/target/riscv/csr.c > +++ b/target/riscv/csr.c > @@ -1834,8 +1834,11 @@ static RISCVException write_mcountinhibit(CPURISCVState *env, int csrno, > { > int cidx; > PMUCTRState *counter; > + RISCVCPU *cpu = env_archcpu(env); > > - env->mcountinhibit = val; > + /* WARL register - disable unavailable counters; TM bit is always 0 */ > + env->mcountinhibit = > + val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | COUNTEREN_IR); > > /* Check if any other counter is also monitoring cycles/instructions */ > for (cidx = 0; cidx < RV_MAX_MHPMCOUNTERS; cidx++) { > @@ -1858,7 +1861,11 @@ static RISCVException read_mcounteren(CPURISCVState *env, int csrno, > static RISCVException write_mcounteren(CPURISCVState *env, int csrno, > target_ulong val) > { > - env->mcounteren = val; > + RISCVCPU *cpu = env_archcpu(env); > + > + /* WARL register - disable unavailable counters */ > + env->mcounteren = val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | COUNTEREN_TM | > + COUNTEREN_IR); > return RISCV_EXCP_NONE; > } > > -- > 2.41.0 > > LGTM. Reviewed-by: Atish Patra <atishp@rivosinc.com>
On Wed, Aug 2, 2023 at 8:50 AM Rob Bradford <rbradford@rivosinc.com> wrote: > > These are WARL fields - zero out the bits for unavailable counters and > special case the TM bit in mcountinhibit which is hardwired to zero. > This patch achieves this by modifying the value written so that any use > of the field will see the correctly masked bits. > > Tested by modifying OpenSBI to write max value to these CSRs and upon > subsequent read the appropriate number of bits for number of PMUs is > enabled and the TM bit is zero in mcountinhibit. > > Signed-off-by: Rob Bradford <rbradford@rivosinc.com> Acked-by: Alistair Francis <alistair.francis@wdc.com> Alistair > --- > target/riscv/csr.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/target/riscv/csr.c b/target/riscv/csr.c > index ea7585329e..495ff6a9c2 100644 > --- a/target/riscv/csr.c > +++ b/target/riscv/csr.c > @@ -1834,8 +1834,11 @@ static RISCVException write_mcountinhibit(CPURISCVState *env, int csrno, > { > int cidx; > PMUCTRState *counter; > + RISCVCPU *cpu = env_archcpu(env); > > - env->mcountinhibit = val; > + /* WARL register - disable unavailable counters; TM bit is always 0 */ > + env->mcountinhibit = > + val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | COUNTEREN_IR); > > /* Check if any other counter is also monitoring cycles/instructions */ > for (cidx = 0; cidx < RV_MAX_MHPMCOUNTERS; cidx++) { > @@ -1858,7 +1861,11 @@ static RISCVException read_mcounteren(CPURISCVState *env, int csrno, > static RISCVException write_mcounteren(CPURISCVState *env, int csrno, > target_ulong val) > { > - env->mcounteren = val; > + RISCVCPU *cpu = env_archcpu(env); > + > + /* WARL register - disable unavailable counters */ > + env->mcounteren = val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | COUNTEREN_TM | > + COUNTEREN_IR); > return RISCV_EXCP_NONE; > } > > -- > 2.41.0 > >
On Wed, Aug 2, 2023 at 8:50 AM Rob Bradford <rbradford@rivosinc.com> wrote: > > These are WARL fields - zero out the bits for unavailable counters and > special case the TM bit in mcountinhibit which is hardwired to zero. > This patch achieves this by modifying the value written so that any use > of the field will see the correctly masked bits. > > Tested by modifying OpenSBI to write max value to these CSRs and upon > subsequent read the appropriate number of bits for number of PMUs is > enabled and the TM bit is zero in mcountinhibit. > > Signed-off-by: Rob Bradford <rbradford@rivosinc.com> Thanks! Applied to riscv-to-apply.next Alistair > --- > target/riscv/csr.c | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/target/riscv/csr.c b/target/riscv/csr.c > index ea7585329e..495ff6a9c2 100644 > --- a/target/riscv/csr.c > +++ b/target/riscv/csr.c > @@ -1834,8 +1834,11 @@ static RISCVException write_mcountinhibit(CPURISCVState *env, int csrno, > { > int cidx; > PMUCTRState *counter; > + RISCVCPU *cpu = env_archcpu(env); > > - env->mcountinhibit = val; > + /* WARL register - disable unavailable counters; TM bit is always 0 */ > + env->mcountinhibit = > + val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | COUNTEREN_IR); > > /* Check if any other counter is also monitoring cycles/instructions */ > for (cidx = 0; cidx < RV_MAX_MHPMCOUNTERS; cidx++) { > @@ -1858,7 +1861,11 @@ static RISCVException read_mcounteren(CPURISCVState *env, int csrno, > static RISCVException write_mcounteren(CPURISCVState *env, int csrno, > target_ulong val) > { > - env->mcounteren = val; > + RISCVCPU *cpu = env_archcpu(env); > + > + /* WARL register - disable unavailable counters */ > + env->mcounteren = val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | COUNTEREN_TM | > + COUNTEREN_IR); > return RISCV_EXCP_NONE; > } > > -- > 2.41.0 > >
diff --git a/target/riscv/csr.c b/target/riscv/csr.c index ea7585329e..495ff6a9c2 100644 --- a/target/riscv/csr.c +++ b/target/riscv/csr.c @@ -1834,8 +1834,11 @@ static RISCVException write_mcountinhibit(CPURISCVState *env, int csrno, { int cidx; PMUCTRState *counter; + RISCVCPU *cpu = env_archcpu(env); - env->mcountinhibit = val; + /* WARL register - disable unavailable counters; TM bit is always 0 */ + env->mcountinhibit = + val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | COUNTEREN_IR); /* Check if any other counter is also monitoring cycles/instructions */ for (cidx = 0; cidx < RV_MAX_MHPMCOUNTERS; cidx++) { @@ -1858,7 +1861,11 @@ static RISCVException read_mcounteren(CPURISCVState *env, int csrno, static RISCVException write_mcounteren(CPURISCVState *env, int csrno, target_ulong val) { - env->mcounteren = val; + RISCVCPU *cpu = env_archcpu(env); + + /* WARL register - disable unavailable counters */ + env->mcounteren = val & (cpu->pmu_avail_ctrs | COUNTEREN_CY | COUNTEREN_TM | + COUNTEREN_IR); return RISCV_EXCP_NONE; }
These are WARL fields - zero out the bits for unavailable counters and special case the TM bit in mcountinhibit which is hardwired to zero. This patch achieves this by modifying the value written so that any use of the field will see the correctly masked bits. Tested by modifying OpenSBI to write max value to these CSRs and upon subsequent read the appropriate number of bits for number of PMUs is enabled and the TM bit is zero in mcountinhibit. Signed-off-by: Rob Bradford <rbradford@rivosinc.com> --- target/riscv/csr.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)