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 16:53, David Gibson wrote:
> On Thu, Jan 18, 2018 at 04:44:28PM +1100, Alexey Kardashevskiy wrote:
>> 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?
> 
> Because what's the guest supposed to do with it. 

"oops"

> This is an internal
> qemu problem, so it should be dealt with via an internal qemu
> mechanism.

Do we have assert() enabled in production? If not, then assert == noop,
error_report is just a noise.



-- 
Alexey


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