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Re: [Qemu-ppc] [RFC for-2.12 8/8] spapr: Handle Decimal Floating Point (
From: |
Greg Kurz |
Subject: |
Re: [Qemu-ppc] [RFC for-2.12 8/8] spapr: Handle Decimal Floating Point (DFP) as an optional capability |
Date: |
Tue, 12 Dec 2017 13:58:48 +0100 |
On Mon, 11 Dec 2017 18:08:08 +1100
David Gibson <address@hidden> wrote:
> Decimal Floating Point has been available on POWER7 and later (server)
> cpus. However, it can be disabled on the hypervisor, meaning that it's
> not available to guests.
>
> We currently handle this by conditionally advertising DFP support in the
> device tree depending on whether the guest CPU model supports it - which
> can also depend on what's allowed in the host for -cpu host. That can lead
> to confusion on migration, since host properties are silently affecting
> guest visible properties.
>
> This patch handles it by treating it as an optional capability for the
> pseries machine type.
>
> Signed-off-by: David Gibson <address@hidden>
> ---
> hw/ppc/spapr.c | 5 +++--
> hw/ppc/spapr_caps.c | 17 +++++++++++++++++
> include/hw/ppc/spapr.h | 3 +++
> 3 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 6b37511e8f..cca3789b35 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -571,7 +571,7 @@ static void spapr_populate_cpu_dt(CPUState *cs, void
> *fdt, int offset,
> /* Advertise DFP (Decimal Floating Point) if available
> * 0 / no property == no DFP
> * 1 == DFP available */
> - if (env->insns_flags2 & PPC2_DFP) {
> + if (spapr_has_cap(spapr, SPAPR_CAP_DFP)) {
> _FDT((fdt_setprop_cell(fdt, offset, "ibm,dfp", 1)));
> }
>
> @@ -3831,7 +3831,8 @@ static void spapr_machine_class_init(ObjectClass *oc,
> void *data)
> */
> mc->numa_mem_align_shift = 28;
>
> - smc->default_caps = spapr_caps(SPAPR_CAP_HTM | SPAPR_CAP_VSX);
> + smc->default_caps = spapr_caps(SPAPR_CAP_HTM | SPAPR_CAP_VSX
> + | SPAPR_CAP_DFP);
> spapr_capability_properties(smc, &error_abort);
> }
>
> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> index b19a9f4417..49c2e10d27 100644
> --- a/hw/ppc/spapr_caps.c
> +++ b/hw/ppc/spapr_caps.c
> @@ -49,6 +49,11 @@ static sPAPRCapabilityInfo capability_table[] = {
> .description = "Allow Vector Scalar Extensions (VSX)",
> .bit = SPAPR_CAP_VSX,
> },
> + {
> + .name = "dfp",
> + .description = "Allow Decimal Floating Point (DFP)",
> + .bit = SPAPR_CAP_DFP,
> + },
> };
>
> static sPAPRCapabilities default_caps_with_cpu(sPAPRMachineState *spapr,
> CPUState *cs)
> @@ -67,6 +72,7 @@ static sPAPRCapabilities
> default_caps_with_cpu(sPAPRMachineState *spapr, CPUStat
> if (!ppc_check_compat(cpu, CPU_POWERPC_LOGICAL_2_06,
> 0, spapr->max_compat_pvr)) {
> caps.mask &= ~SPAPR_CAP_VSX;
> + caps.mask &= ~SPAPR_CAP_DFP;
> }
>
> return caps;
> @@ -184,6 +190,13 @@ static void spapr_allow_caps(sPAPRMachineState *spapr,
> Error **errp)
> }
> }
>
> + if (spapr_has_cap(spapr, SPAPR_CAP_DFP)) {
> + if (!(env->insns_flags2 & PPC2_DFP)) {
> + error_setg(&err, "DFP support not available, try cap-dfp=off");
> + goto out;
> + }
> + }
> +
> out:
> if (err) {
> error_propagate(errp, err);
> @@ -199,6 +212,10 @@ static void spapr_enforce_caps(sPAPRMachineState *spapr,
> Error **errp)
> if (!spapr_has_cap(spapr, SPAPR_CAP_VSX)) {
> /* TODO: Any way to disable VSX? */
> }
> +
> + if (!spapr_has_cap(spapr, SPAPR_CAP_VSX)) {
s/SPAPR_CAP_VSX/SPAPR_CAP_DFP/
With that fixed:
Reviewed-by: Greg Kurz <address@hidden>
> + /* TODO: Any way to disable DFP? */
> + }
> }
>
> void spapr_caps_reset(sPAPRMachineState *spapr)
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 4c173cb40c..ef4f7427de 100644
> --- a/include/hw/ppc/spapr.h
> +++ b/include/hw/ppc/spapr.h
> @@ -62,6 +62,9 @@ typedef enum {
> /* Vector Scalar Extensions */
> #define SPAPR_CAP_VSX 0x0000000000000002ULL
>
> +/* Decimal Floating Point */
> +#define SPAPR_CAP_DFP 0x0000000000000004ULL
> +
> typedef struct sPAPRCapabilities sPAPRCapabilities;
> struct sPAPRCapabilities {
> uint64_t mask;