From 747a43e818dc36bd50ef98c2b11a7c31ceb810fa Mon Sep 17 00:00:00 2001 From: Alistair Francis Date: Mon, 17 Jun 2019 18:31:08 -0700 Subject: [PATCH] target/riscv: Add the mcountinhibit CSR 1.11 defines mcountinhibit, which has the same numeric CSR value as mucounteren from 1.09.1 but has different semantics. This patch enables the CSR for 1.11-based targets, which is trivial to implement because the counters in QEMU never tick (legal according to the spec). Signed-off-by: Alistair Francis [Palmer: Fix counter access semantics, change commit message to indicate the behavior is fully emulated.] Reviewed-by: Palmer Dabbelt Signed-off-by: Palmer Dabbelt --- target/riscv/cpu_bits.h | 1 + target/riscv/csr.c | 17 +++++++++++++++-- 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h index 47450a3cdb..11f971ad5d 100644 --- a/target/riscv/cpu_bits.h +++ b/target/riscv/cpu_bits.h @@ -136,6 +136,7 @@ #define CSR_MCOUNTEREN 0x306 /* Legacy Counter Setup (priv v1.9.1) */ +/* Update to #define CSR_MCOUNTINHIBIT 0x320 for 1.11.0 */ #define CSR_MUCOUNTEREN 0x320 #define CSR_MSCOUNTEREN 0x321 #define CSR_MHCOUNTEREN 0x322 diff --git a/target/riscv/csr.c b/target/riscv/csr.c index c67d29e206..448162e484 100644 --- a/target/riscv/csr.c +++ b/target/riscv/csr.c @@ -56,6 +56,15 @@ static int fs(CPURISCVState *env, int csrno) static int ctr(CPURISCVState *env, int csrno) { #if !defined(CONFIG_USER_ONLY) + /* + * The counters are always enabled on newer priv specs, as the CSR has + * changed from controlling that the counters can be read to controlling + * that the counters increment. + */ + if (env->priv_ver > PRIV_VERSION_1_09_1) { + return 0; + } + uint32_t ctr_en = ~0u; if (env->priv < PRV_M) { @@ -461,18 +470,22 @@ static int write_mcounteren(CPURISCVState *env, int csrno, target_ulong val) return 0; } +/* This regiser is replaced with CSR_MCOUNTINHIBIT in 1.11.0 */ static int read_mscounteren(CPURISCVState *env, int csrno, target_ulong *val) { - if (env->priv_ver > PRIV_VERSION_1_09_1) { + if (env->priv_ver > PRIV_VERSION_1_09_1 + && env->priv_ver < PRIV_VERSION_1_11_0) { return -1; } *val = env->mcounteren; return 0; } +/* This regiser is replaced with CSR_MCOUNTINHIBIT in 1.11.0 */ static int write_mscounteren(CPURISCVState *env, int csrno, target_ulong val) { - if (env->priv_ver > PRIV_VERSION_1_09_1) { + if (env->priv_ver > PRIV_VERSION_1_09_1 + && env->priv_ver < PRIV_VERSION_1_11_0) { return -1; } env->mcounteren = val;