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

[David Gibson]

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 <address@hidden>
> >> ---
> >>  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.  This is an internal
qemu problem, so it should be dealt with via an internal qemu
mechanism.

-- 
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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