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Re: [Qemu-devel] [QEMU-PPC] [PATCH 4/4] target/ppc/spapr: Enable the lar
From: |
Suraj Jitindar Singh |
Subject: |
Re: [Qemu-devel] [QEMU-PPC] [PATCH 4/4] target/ppc/spapr: Enable the large decrementer by default on POWER9 |
Date: |
Wed, 27 Feb 2019 10:50:52 +1100 |
On Tue, 2019-02-26 at 14:59 +1100, David Gibson wrote:
> On Tue, Feb 26, 2019 at 02:05:31PM +1100, Suraj Jitindar Singh wrote:
> > Enable the large decrementer by default on POWER9 cpu models. The
> > default value applied is that provided in the cpu class.
> >
> > Signed-off-by: Suraj Jitindar Singh <address@hidden>
> > ---
> > hw/ppc/spapr_caps.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> > index e07568fb94..f48aa367e3 100644
> > --- a/hw/ppc/spapr_caps.c
> > +++ b/hw/ppc/spapr_caps.c
> > @@ -566,11 +566,18 @@ sPAPRCapabilityInfo
> > capability_table[SPAPR_CAP_NUM] = {
> > static sPAPRCapabilities default_caps_with_cpu(sPAPRMachineState
> > *spapr,
> > const char
> > *cputype)
> > {
> > + PowerPCCPUClass *pcc =
> > POWERPC_CPU_CLASS(object_class_by_name(cputype));
> > sPAPRMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
> > sPAPRCapabilities caps;
> >
> > caps = smc->default_caps;
> >
> > + caps.caps[SPAPR_CAP_LARGE_DECREMENTER] = pcc->hdecr_bits;
>
> So, the rule with default_caps_with_cpu() is that it can reduce the
> value from the machine-global default, but never increase it (because
> that could change guest visible behaviour for existing machine
> versions).
>
> I think the line above will do that.
Yep
>
> > + if (!ppc_type_check_compat(cputype, CPU_POWERPC_LOGICAL_3_00,
> > + 0, spapr->max_compat_pvr)) {
> > + caps.caps[SPAPR_CAP_LARGE_DECREMENTER] = 0;
>
> And this part I think is redundant, because hdecr_bits won't be large
> for anything pre-POWER9.
>
> > + }
> > +
> > if (!ppc_type_check_compat(cputype, CPU_POWERPC_LOGICAL_2_07,
> > 0, spapr->max_compat_pvr)) {
> > caps.caps[SPAPR_CAP_HTM] = SPAPR_CAP_OFF;
>
>
Re: [Qemu-devel] [QEMU-PPC] [PATCH 1/4] target/ppc/spapr: Add SPAPR_CAP_LARGE_DECREMENTER, David Gibson, 2019/02/25