Re: [PATCH 1/3] target/arm: Honor HCR_EL2.TID2 trapping requirements

["Edgar E. Iglesias" <edgar.iglesias@gmail.com>]

On Thu, Nov 28, 2019 at 04:17:16PM +0000, Marc Zyngier wrote:
> HCR_EL2.TID2 mandates that access from EL1 to CTR_EL0, CCSIDR_EL1,
> CCSIDR2_EL1, CLIDR_EL1, CSSELR_EL1 are trapped to EL2, and QEMU
> completely ignores it, making impossible for hypervisors to

Nit: "making it impossible"


> virtualize the cache hierarchy.
> 
> Do the right thing by trapping to EL2 if HCR_EL2.TID2 is set.
> 
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
>  target/arm/helper.c | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 0bf8f53d4b..0b6887b100 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -1910,6 +1910,17 @@ static void scr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
>      raw_write(env, ri, value);
>  }
>  
> +static CPAccessResult access_aa64_tid2(CPUARMState *env,
> +                                       const ARMCPRegInfo *ri,
> +                                       bool isread)
> +{
> +    if (arm_current_el(env) == 1 && (arm_hcr_el2_eff(env) & HCR_TID2)) {
> +        return CP_ACCESS_TRAP_EL2;
> +    }
> +
> +    return CP_ACCESS_OK;
> +}
> +
>  static uint64_t ccsidr_read(CPUARMState *env, const ARMCPRegInfo *ri)
>  {
>      ARMCPU *cpu = env_archcpu(env);
> @@ -2110,10 +2121,14 @@ static const ARMCPRegInfo v7_cp_reginfo[] = {
>        .writefn = pmintenclr_write },
>      { .name = "CCSIDR", .state = ARM_CP_STATE_BOTH,
>        .opc0 = 3, .crn = 0, .crm = 0, .opc1 = 1, .opc2 = 0,
> -      .access = PL1_R, .readfn = ccsidr_read, .type = ARM_CP_NO_RAW },
> +      .access = PL1_R,
> +      .accessfn = access_aa64_tid2,
> +      .readfn = ccsidr_read, .type = ARM_CP_NO_RAW },
>      { .name = "CSSELR", .state = ARM_CP_STATE_BOTH,
>        .opc0 = 3, .crn = 0, .crm = 0, .opc1 = 2, .opc2 = 0,
> -      .access = PL1_RW, .writefn = csselr_write, .resetvalue = 0,
> +      .access = PL1_RW,
> +      .accessfn = access_aa64_tid2,
> +      .writefn = csselr_write, .resetvalue = 0,
>        .bank_fieldoffsets = { offsetof(CPUARMState, cp15.csselr_s),
>                               offsetof(CPUARMState, cp15.csselr_ns) } },
>      /* Auxiliary ID register: this actually has an IMPDEF value but for now
> @@ -5204,6 +5219,11 @@ static CPAccessResult ctr_el0_access(CPUARMState *env, const ARMCPRegInfo *ri,
>      if (arm_current_el(env) == 0 && !(env->cp15.sctlr_el[1] & SCTLR_UCT)) {
>          return CP_ACCESS_TRAP;
>      }
> +
> +    if (arm_hcr_el2_eff(env) & HCR_TID2) {
> +        return CP_ACCESS_TRAP_EL2;
> +    }


Shouldn't we also be checking that we're in EL < 2 when trapping?

Also, I think we need to somehow hook in access_aa64_tid2() for the AArch32
view of CTR, don't we?

Cheers,
Edgar


> +
>      return CP_ACCESS_OK;
>  }
>  
> @@ -6184,7 +6204,9 @@ void register_cp_regs_for_features(ARMCPU *cpu)
>          ARMCPRegInfo clidr = {
>              .name = "CLIDR", .state = ARM_CP_STATE_BOTH,
>              .opc0 = 3, .crn = 0, .crm = 0, .opc1 = 1, .opc2 = 1,
> -            .access = PL1_R, .type = ARM_CP_CONST, .resetvalue = cpu->clidr
> +            .access = PL1_R, .type = ARM_CP_CONST,
> +            .accessfn = access_aa64_tid2,
> +            .resetvalue = cpu->clidr
>          };
>          define_one_arm_cp_reg(cpu, &clidr);
>          define_arm_cp_regs(cpu, v7_cp_reginfo);
> -- 
> 2.20.1
> 
> 
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