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

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jan 18, 2018 at 07:11:41PM +1100, Alexey Kardashevskiy wrote:
> 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"

Thereby making what is definitely a qemu bug appear to be a guest
problem.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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