Re: [Qemu-devel] [Qemu-ppc] [QEMU-PPC] [PATCH V3 6/6] target/ppc/spapr: Add H-Call H_GET_CPU_CHARACTERISTICS

[Alexey Kardashevskiy <aik@ozlabs.ru>]

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On 18/01/18 16:20, David Gibson wrote:
> On Mon, Jan 15, 2018 at 05:32:35PM +1100, Suraj Jitindar Singh wrote:
>> The new H-Call H_GET_CPU_CHARACTERISTICS is used by the guest to query
>> behaviours and available characteristics of the cpu.
>>
>> Implement the handler for this new H-Call which formulates its response
>> based on the setting of the spapr_caps cap-cfpc, cap-sbbc and cap-ibs.
>>
>> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
>> ---
>>  hw/ppc/spapr_hcall.c   | 66 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>  include/hw/ppc/spapr.h |  1 +
>>  2 files changed, 67 insertions(+)
>>
>> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
>> index 51eba52e86..a693d3b852 100644
>> --- a/hw/ppc/spapr_hcall.c
>> +++ b/hw/ppc/spapr_hcall.c
>> @@ -1654,6 +1654,69 @@ static target_ulong h_client_architecture_support(PowerPCCPU *cpu,
>>      return H_SUCCESS;
>>  }
>>  
>> +static target_ulong h_get_cpu_characteristics(PowerPCCPU *cpu,
>> +                                              sPAPRMachineState *spapr,
>> +                                              target_ulong opcode,
>> +                                              target_ulong *args)
>> +{
>> +    uint64_t characteristics = H_CPU_CHAR_HON_BRANCH_HINTS &
>> +			       ~H_CPU_CHAR_THR_RECONF_TRIG;
>> +    uint64_t behaviour = H_CPU_BEHAV_FAVOUR_SECURITY;
>> +    uint8_t safe_cache = spapr_get_cap(spapr, SPAPR_CAP_CFPC);
>> +    uint8_t safe_bounds_check = spapr_get_cap(spapr, SPAPR_CAP_SBBC);
>> +    uint8_t safe_indirect_branch = spapr_get_cap(spapr, SPAPR_CAP_IBS);
>> +
>> +    switch (safe_cache) {
>> +    case SPAPR_CAP_WORKAROUND:
>> +        characteristics |= H_CPU_CHAR_L1D_FLUSH_ORI30;
>> +        characteristics |= H_CPU_CHAR_L1D_FLUSH_TRIG2;
>> +        characteristics |= H_CPU_CHAR_L1D_THREAD_PRIV;
>> +        behaviour |= H_CPU_BEHAV_L1D_FLUSH_PR;
>> +        break;
>> +    case SPAPR_CAP_FIXED:
>> +        break;
>> +    default: /* broken */
>> +        if (safe_cache != SPAPR_CAP_BROKEN) {
> 
> I think you just assert() for this.  The only way these could get a
> different value is if there's a bug elsewhere.


Why not return H_HARDWARE or other error?



-- 
Alexey


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