On Mon, 18 Dec 2017 20:20:24 +1100
David Gibson <da...@gibson.dropbear.id.au> 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 <da...@gibson.dropbear.id.au>
> ---
Reviewed-by: Greg Kurz <gr...@kaod.org>
> hw/ppc/spapr.c | 7 ++++---
> hw/ppc/spapr_caps.c | 18 ++++++++++++++++++
> include/hw/ppc/spapr.h | 3 +++
> 3 files changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 693dd6f7b3..e22888ba06 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -572,7 +572,7 @@ 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)));
> }
>
> @@ -3834,7 +3834,7 @@ static void spapr_machine_class_init(ObjectClass *oc,
> void *data)
> */
> mc->numa_mem_align_shift = 28;
>
> - smc->default_caps = spapr_caps(SPAPR_CAP_VSX);
> + smc->default_caps = spapr_caps(SPAPR_CAP_VSX | SPAPR_CAP_DFP);
> spapr_caps_add_properties(smc, &error_abort);
> }
>
> @@ -3916,7 +3916,8 @@ static void
> spapr_machine_2_11_class_options(MachineClass *mc)
> sPAPRMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
>
> spapr_machine_2_12_class_options(mc);
> - 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);
> SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_11);
> }
>
> diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> index da066aec8f..61745f0b32 100644
> --- a/hw/ppc/spapr_caps.c
> +++ b/hw/ppc/spapr_caps.c
> @@ -70,6 +70,16 @@ static void cap_vsx_allow(sPAPRMachineState *spapr, Error
> **errp)
> }
> }
>
> +static void cap_dfp_allow(sPAPRMachineState *spapr, Error **errp)
> +{
> + PowerPCCPU *cpu = POWERPC_CPU(first_cpu);
> + CPUPPCState *env = &cpu->env;
> +
> + if (!(env->insns_flags2 & PPC2_DFP)) {
> + error_setg(errp, "DFP support not available, try cap-dfp=off");
> + }
> +}
> +
> static sPAPRCapabilityInfo capability_table[] = {
> {
> .name = "htm",
> @@ -85,6 +95,13 @@ static sPAPRCapabilityInfo capability_table[] = {
> .allow = cap_vsx_allow,
> /* TODO: add cap_vsx_disallow */
> },
> + {
> + .name = "dfp",
> + .description = "Allow Decimal Floating Point (DFP)",
> + .flag = SPAPR_CAP_DFP,
> + .allow = cap_dfp_allow,
> + /* TODO: add cap_dfp_disallow */
> + },
> };
>
> static sPAPRCapabilities default_caps_with_cpu(sPAPRMachineState *spapr,
> @@ -104,6 +121,7 @@ static sPAPRCapabilities
> default_caps_with_cpu(sPAPRMachineState *spapr,
> 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;
> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> index 148a03d189..26ac17e641 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;
