Re: [Qemu-devel] [PATCH] ARM64: support access to more performance registers in AA64 mode

[Christopher Covington <cov@codeaurora.org>]

Hi Chengyu,

On 12/03/2014 02:12 AM, Chengyu Song wrote:
> In AA64 mode, certain system registers are access through MSR/MRS 
> instructions instead of MCR/MRC. This patch added more such registers:

If you don't mind sharing, I'm curious what motivated this patch. I have a
particular interest in having `perf stat -e instructions:u echo` inside
qemu-system-aarch64 function correctly, and this looks like a good step in
that direction.

> /* ARMv8 manual, D8.4.10 */
> PMINTENCLR_EL1

It'd probably good to mention the version of the document.

> /* ARMv8 manual, D8.4.11 */
> PMINTENSET_EL1
> 
> /* ARMv8 manual, D8.4.12 */
> PMOVSCLR_EL0
> 
> /* ARMv8 manual, D8.4.14 */
> PMSELR_EL0
> 
> /* ARMv8 manual, D8.4.15 */
> PMSWINC_EL0
> 
> /* ARMv8 manual, D8.4.16 */
> PMUSERENR_EL0
> 
> /* ARMv8 manual, D8.4.17 */
> PMXEVCNTR_EL0
> 
> /* ARMv8 manual, D8.4.18 */
> PMXEVTYPER_EL0
> 
> Signed-off-by: Chengyu Song <csong84@gatech.edu>
> ---
>  target-arm/helper.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index b74d348..43b5b06 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -843,15 +843,28 @@ static const ARMCPRegInfo v7_cp_reginfo[] = {
>        .accessfn = pmreg_access,
>        .writefn = pmovsr_write,
>        .raw_writefn = raw_write },
> +    { .name = "PMOVSCLR_EL0", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .crn = 9, .crm = 12, .opc1 = 3, .opc2 = 3,

It might be helpful to order the fields opc0, opc1, crn, crm, opc2 to match
the documentation and some (most?) of the other A64 QEMU code.

> +      .access = PL0_RW, .fieldoffset = offsetof(CPUARMState, cp15.c9_pmovsr),
> +      .accessfn = pmreg_access,
> +      .writefn = pmovsr_write,
> +      .raw_writefn = raw_write },

Should this contain .type = ARM_CP_NO_MIGRATE, if PMOVSCLR_EL0, PMOVSSET_EL0,
and PMOVSR all refer to the same underlying variable?

Should PMOVSSET_EL0 also be added?

>      /* Unimplemented so WI. */
>      { .name = "PMSWINC", .cp = 15, .crn = 9, .crm = 12, .opc1 = 0, .opc2 = 4,
>        .access = PL0_W, .accessfn = pmreg_access, .type = ARM_CP_NOP },
> +    { .name = "PMSWINC_EL0", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .crn = 9, .crm = 12, .opc1 = 3, .opc2 = 4,
> +      .access = PL0_W, .accessfn = pmreg_access, .type = ARM_CP_NOP },
>      /* Since we don't implement any events, writing to PMSELR is UNPREDICTABLE.
>       * We choose to RAZ/WI.
>       */
>      { .name = "PMSELR", .cp = 15, .crn = 9, .crm = 12, .opc1 = 0, .opc2 = 5,
>        .access = PL0_RW, .type = ARM_CP_CONST, .resetvalue = 0,
>        .accessfn = pmreg_access },
> +    { .name = "PMSELR_EL0", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .crn = 9, .crm = 12, .opc1 = 3, .opc2 = 5,
> +      .access = PL0_RW, .type = ARM_CP_CONST, .resetvalue = 0,
> +      .accessfn = pmreg_access },
>  #ifndef CONFIG_USER_ONLY
>      { .name = "PMCCNTR", .cp = 15, .crn = 9, .crm = 13, .opc1 = 0, .opc2 = 0,
>        .access = PL0_RW, .resetvalue = 0, .type = ARM_CP_IO,
> @@ -875,24 +888,51 @@ static const ARMCPRegInfo v7_cp_reginfo[] = {
>        .fieldoffset = offsetof(CPUARMState, cp15.c9_pmxevtyper),
>        .accessfn = pmreg_access, .writefn = pmxevtyper_write,
>        .raw_writefn = raw_write },
> +    { .name = "PMXEVTYPER_EL0", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .crn = 9, .crm = 13, .opc1 = 3, .opc2 = 1,
> +      .access = PL0_RW,
> +      .fieldoffset = offsetof(CPUARMState, cp15.c9_pmxevtyper),
> +      .accessfn = pmreg_access, .writefn = pmxevtyper_write,
> +      .raw_writefn = raw_write },
>      /* Unimplemented, RAZ/WI. */
>      { .name = "PMXEVCNTR", .cp = 15, .crn = 9, .crm = 13, .opc1 = 0, .opc2 = 2,
>        .access = PL0_RW, .type = ARM_CP_CONST, .resetvalue = 0,
>        .accessfn = pmreg_access },
> +    { .name = "PMXEVCNTR_EL0", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .crn = 9, .crm = 13, .opc1 = 3, .opc2 = 2,
> +      .access = PL0_RW, .type = ARM_CP_CONST, .resetvalue = 0,
> +      .accessfn = pmreg_access },
>      { .name = "PMUSERENR", .cp = 15, .crn = 9, .crm = 14, .opc1 = 0, .opc2 = 0,
>        .access = PL0_R | PL1_RW,
>        .fieldoffset = offsetof(CPUARMState, cp15.c9_pmuserenr),
>        .resetvalue = 0,
>        .writefn = pmuserenr_write, .raw_writefn = raw_write },
> +    { .name = "PMUSERENR_EL0", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .crn = 9, .crm = 14, .opc1 = 3, .opc2 = 0,
> +      .access = PL0_R | PL1_RW,
> +      .fieldoffset = offsetof(CPUARMState, cp15.c9_pmuserenr),
> +      .resetvalue = 0,
> +      .writefn = pmuserenr_write, .raw_writefn = raw_write },

Again, should .type = ARM_CP_NO_MIGRATE be used as this shares a variable with
PMUSERENR?

>      { .name = "PMINTENSET", .cp = 15, .crn = 9, .crm = 14, .opc1 = 0, .opc2 = 1,
>        .access = PL1_RW,
>        .fieldoffset = offsetof(CPUARMState, cp15.c9_pminten),
>        .resetvalue = 0,
>        .writefn = pmintenset_write, .raw_writefn = raw_write },
> +    { .name = "PMINTENSET_EL1", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .crn = 9, .crm = 14, .opc1 = 0, .opc2 = 1,
> +      .access = PL1_RW,
> +      .fieldoffset = offsetof(CPUARMState, cp15.c9_pminten),
> +      .resetvalue = 0,
> +      .writefn = pmintenset_write, .raw_writefn = raw_write },

Again, should .type = ARM_CP_NO_MIGRATE be used as this shares a variable with
PMINTSET?

>      { .name = "PMINTENCLR", .cp = 15, .crn = 9, .crm = 14, .opc1 = 0, .opc2 = 2,
>        .access = PL1_RW, .type = ARM_CP_NO_MIGRATE,
>        .fieldoffset = offsetof(CPUARMState, cp15.c9_pminten),
>        .resetvalue = 0, .writefn = pmintenclr_write, },
> +    { .name = "PMINTENCLR_EL1", .state = ARM_CP_STATE_AA64,
> +      .opc0 = 3, .crn = 9, .crm = 14, .opc1 = 0, .opc2 = 2,
> +      .access = PL1_RW, .type = ARM_CP_NO_MIGRATE,
> +      .fieldoffset = offsetof(CPUARMState, cp15.c9_pminten),
> +      .resetvalue = 0, .writefn = pmintenclr_write, },
>      { .name = "VBAR", .state = ARM_CP_STATE_BOTH,
>        .opc0 = 3, .crn = 12, .crm = 0, .opc1 = 0, .opc2 = 0,
>        .access = PL1_RW, .writefn = vbar_write,

Thanks,
Chris

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