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target/riscv: Add the mcountinhibit CSR

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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 <alistair.francis@wdc.com>
[Palmer: Fix counter access semantics, change commit message to indicate
the behavior is fully emulated.]
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
This commit is contained in:
Alistair Francis 2019-06-17 18:31:08 -07:00 committed by Palmer Dabbelt
parent 6729dbbd42
commit 747a43e818
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GPG key ID: EF4CA1502CCBAB41
2 changed files with 16 additions and 2 deletions
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1
target/riscv/cpu_bits.h
View file

@ -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

17
target/riscv/csr.c
View file

@ -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;