Re: [Qemu-devel] [PATCH v2 4/9] target-arm: Add AArch64 CPTR registers

[Peter Maydell]

On 22 April 2015 at 18:09, Greg Bellows <address@hidden> wrote:
> Adds CPTR_EL2/3 system registers definitions and access function.
>
> Signed-off-by: Greg Bellows <address@hidden>
>
> ---
>
> v2 -> v3
> - Broke out cptr and cpacr access functions
> - Added HCPTR register entry as alias of CPTR_EL2
> - Added HCPTR and CPTR_EL2 no_el2 register entries.
> - Fixed cptr_access comment
> ---
>  target-arm/cpu.h    |  5 +++++
>  target-arm/helper.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 54 insertions(+), 1 deletion(-)
>
> diff --git a/target-arm/cpu.h b/target-arm/cpu.h
> index 2178a1f..d61bb3f 100644
> --- a/target-arm/cpu.h
> +++ b/target-arm/cpu.h
> @@ -202,6 +202,7 @@ typedef struct CPUARMState {
>              uint64_t sctlr_el[4];
>          };
>          uint64_t c1_coproc; /* Coprocessor access register.  */
> +        uint64_t cptr_el[4];  /* ARMv8 feature trap registers */
>          uint32_t c1_xscaleauxcr; /* XScale auxiliary control register.  */
>          uint64_t sder; /* Secure debug enable register. */
>          uint32_t nsacr; /* Non-secure access control register. */
> @@ -575,6 +576,10 @@ void pmccntr_sync(CPUARMState *env);
>  #define SCTLR_AFE     (1U << 29)
>  #define SCTLR_TE      (1U << 30)
>
> +#define CPTR_TCPAC    (1U << 31)
> +#define CPTR_TTA      (1U << 20)
> +#define CPTR_TFP      (1U << 10)
> +
>  #define CPSR_M (0x1fU)
>  #define CPSR_T (1U << 5)
>  #define CPSR_F (1U << 6)
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index c83d9fc..e36c3d4 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -592,6 +592,34 @@ static void cpacr_write(CPUARMState *env, const 
> ARMCPRegInfo *ri,
>      env->cp15.c1_coproc = value;
>  }
>
> +static CPAccessResult cpacr_access(CPUARMState *env, const ARMCPRegInfo *ri)
> +{
> +    if (arm_feature(env, ARM_FEATURE_V8) && arm_current_el(env) == 1) {
> +        /* Check if CPACR accesses are to be trapped to EL2 */
> +        if ((env->cp15.cptr_el[2] & CPTR_TCPAC) && !arm_is_secure(env)) {
> +            env->exception.target_el = 2;
> +            return CP_ACCESS_TRAP;
> +        /* Check if CPACR accesses are to be trapped to EL3 */
> +        } else if (env->cp15.cptr_el[3] & CPTR_TCPAC) {

CPTR_EL3.TCPAC traps EL2 accesses to CPACR as well as EL1 accesses.

> +            env->exception.target_el = 3;
> +            return CP_ACCESS_TRAP;
> +        }
> +    }
> +
> +    return CP_ACCESS_OK;
> +}
> +
> +static CPAccessResult cptr_access(CPUARMState *env, const ARMCPRegInfo *ri)
> +{
> +    /* Check it CPTR accesses are set to trap to EL3 */

"if"

> +    if (arm_current_el(env) == 2 && (env->cp15.cptr_el[3] & CPTR_TCPAC)) {
> +        env->exception.target_el = 3;
> +        return CP_ACCESS_TRAP;
> +    }
> +
> +    return CP_ACCESS_OK;
> +}
> +
>  static const ARMCPRegInfo v6_cp_reginfo[] = {
>      /* prefetch by MVA in v6, NOP in v7 */
>      { .name = "MVA_prefetch",
> @@ -614,7 +642,7 @@ static const ARMCPRegInfo v6_cp_reginfo[] = {
>      { .name = "WFAR", .cp = 15, .crn = 6, .crm = 0, .opc1 = 0, .opc2 = 1,
>        .access = PL1_RW, .type = ARM_CP_CONST, .resetvalue = 0, },
>      { .name = "CPACR", .state = ARM_CP_STATE_BOTH, .opc0 = 3,
> -      .crn = 1, .crm = 0, .opc1 = 0, .opc2 = 2,
> +      .crn = 1, .crm = 0, .opc1 = 0, .opc2 = 2, .accessfn = cpacr_access,
>        .access = PL1_RW, .fieldoffset = offsetof(CPUARMState, cp15.c1_coproc),
>        .resetvalue = 0, .writefn = cpacr_write },
>      REGINFO_SENTINEL
> @@ -2470,6 +2498,14 @@ static const ARMCPRegInfo v8_el3_no_el2_cp_reginfo[] = 
> {
>        .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 0,
>        .access = PL2_RW,
>        .readfn = arm_cp_read_zero, .writefn = arm_cp_write_ignore },
> +    { .name = "CPTR_EL2", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 2,
> +      .access = PL2_RW, .accessfn = cptr_access, .resetvalue = 0,
> +      .readfn = arm_cp_read_zero, .writefn = arm_cp_write_ignore },
> +    { .name = "HCPTR", .type = ARM_CP_ALIAS,
> +      .cp = 15, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 2,
> +      .access = PL2_RW, .accessfn = cptr_access, .resetvalue = 0,
> +      .readfn = arm_cp_read_zero, .writefn = arm_cp_write_ignore },

These can be merged into a single ARM_CP_STATE_BOTH, using
ARM_CP_CONST is more efficient than using readfns to get the
RAZ/WI behaviour, and we don't need the access function because
it can never trigger for a CPU without EL2:

+    { .name = "CPTR_EL2", .state = ARM_CP_STATE_BOTH,
+      .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 2,
+      .access = PL2_RW, .type = ARM_CP_CONST, .resetvalue = 0 },

>      REGINFO_SENTINEL
>  };
>
> @@ -2537,6 +2573,14 @@ static const ARMCPRegInfo v8_el2_cp_reginfo[] = {
>        .opc0 = 3, .opc1 = 6, .crn = 4, .crm = 1, .opc2 = 0,
>        .access = PL3_RW, .type = ARM_CP_ALIAS,
>        .fieldoffset = offsetof(CPUARMState, sp_el[2]) },
> +    { .name = "CPTR_EL2", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 2,
> +      .access = PL2_RW, .accessfn = cptr_access, .resetvalue = 0,
> +      .fieldoffset = offsetof(CPUARMState, cp15.cptr_el[2]) },
> +    { .name = "HCPTR", .type = ARM_CP_ALIAS,
> +      .cp = 15, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 2,
> +      .access = PL2_RW, .accessfn = cptr_access, .resetvalue = 0,
> +      .fieldoffset = offsetof(CPUARMState, cp15.cptr_el[2]) },

These also can be merged:

+    { .name = "CPTR_EL2", .state = ARM_CP_STATE_BOTH,
+      .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 2,
+      .access = PL2_RW, .accessfn = cptr_access, .resetvalue = 0,
+      .fieldoffset = offsetof(CPUARMState, cp15.cptr_el[2]) },

>      REGINFO_SENTINEL
>  };
>
> @@ -2598,6 +2642,10 @@ static const ARMCPRegInfo el3_cp_reginfo[] = {
>        .access = PL3_RW, .writefn = vbar_write,
>        .fieldoffset = offsetof(CPUARMState, cp15.vbar_el[3]),
>        .resetvalue = 0 },
> +    { .name = "CPTR_EL3", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .opc1 = 6, .crn = 1, .crm = 1, .opc2 = 2,
> +      .access = PL3_RW, .accessfn = cptr_access, .resetvalue = 0,
> +      .fieldoffset = offsetof(CPUARMState, cp15.cptr_el[3]) },
>      REGINFO_SENTINEL
>  };

thanks
-- PMM