| Message ID | 157010411885.246126.12610015369068227139.stgit@bahia.lan |
|---|---|
| State | New |
| Headers | show |
| Series | spapr: Use less XIVE HW resources in KVM | expand |
On Thu, Oct 03, 2019 at 02:02:00PM +0200, Greg Kurz wrote: > Support for setting VSMT is available in KVM since linux-4.13. Most distros > that support KVM on POWER already have it. It thus seem reasonable enough > to have the default machine to set VSMT to smp_threads. > > This brings contiguous VCPU ids and thus brings their upper bound down to > the machine's max_cpus. This is especially useful for XIVE KVM devices, > which may thus allocate only one VP descriptor per VCPU. > > Signed-off-by: Greg Kurz <groug@kaod.org> Applied to ppc-for-4.2, thanks. > --- > hw/ppc/spapr.c | 7 ++++++- > include/hw/ppc/spapr.h | 1 + > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 8f59f08c102e..473ce1d04775 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -2503,6 +2503,7 @@ static CPUArchId *spapr_find_cpu_slot(MachineState *ms, uint32_t id, int *idx) > static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) > { > MachineState *ms = MACHINE(spapr); > + SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr); > Error *local_err = NULL; > bool vsmt_user = !!spapr->vsmt; > int kvm_smt = kvmppc_smt_threads(); > @@ -2529,7 +2530,7 @@ static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) > goto out; > } > /* In this case, spapr->vsmt has been set by the command line */ > - } else { > + } else if (!smc->smp_threads_vsmt) { > /* > * Default VSMT value is tricky, because we need it to be as > * consistent as possible (for migration), but this requires > @@ -2538,6 +2539,8 @@ static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) > * overwhelmingly common case in production systems. > */ > spapr->vsmt = MAX(8, smp_threads); > + } else { > + spapr->vsmt = smp_threads; > } > > /* KVM: If necessary, set the SMT mode: */ > @@ -4452,6 +4455,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data) > smc->irq = &spapr_irq_dual; > smc->dr_phb_enabled = true; > smc->linux_pci_probe = true; > + smc->smp_threads_vsmt = true; > } > > static const TypeInfo spapr_machine_info = { > @@ -4519,6 +4523,7 @@ static void spapr_machine_4_1_class_options(MachineClass *mc) > > spapr_machine_4_2_class_options(mc); > smc->linux_pci_probe = false; > + smc->smp_threads_vsmt = false; > compat_props_add(mc->compat_props, hw_compat_4_1, hw_compat_4_1_len); > compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat)); > } > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h > index cbd1a4c9f390..2009eb64f9cb 100644 > --- a/include/hw/ppc/spapr.h > +++ b/include/hw/ppc/spapr.h > @@ -122,6 +122,7 @@ struct SpaprMachineClass { > bool broken_host_serial_model; /* present real host info to the guest */ > bool pre_4_1_migration; /* don't migrate hpt-max-page-size */ > bool linux_pci_probe; > + bool smp_threads_vsmt; /* set VSMT to smp_threads by default */ > > void (*phb_placement)(SpaprMachineState *spapr, uint32_t index, > uint64_t *buid, hwaddr *pio, >
On Mon, 14 Oct 2019 17:12:47 +1100 David Gibson <david@gibson.dropbear.id.au> wrote: > On Thu, Oct 03, 2019 at 02:02:00PM +0200, Greg Kurz wrote: > > Support for setting VSMT is available in KVM since linux-4.13. Most distros > > that support KVM on POWER already have it. It thus seem reasonable enough > > to have the default machine to set VSMT to smp_threads. > > > > This brings contiguous VCPU ids and thus brings their upper bound down to > > the machine's max_cpus. This is especially useful for XIVE KVM devices, > > which may thus allocate only one VP descriptor per VCPU. > > Just to clarify that without the other patches in this series, XIVE KVM devices still allocate a fixed block of 2048 VPs, no matter what. ie, the last sentence in the changelog may be slightly misleading. > > Signed-off-by: Greg Kurz <groug@kaod.org> > > Applied to ppc-for-4.2, thanks. > > > --- > > hw/ppc/spapr.c | 7 ++++++- > > include/hw/ppc/spapr.h | 1 + > > 2 files changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > > index 8f59f08c102e..473ce1d04775 100644 > > --- a/hw/ppc/spapr.c > > +++ b/hw/ppc/spapr.c > > @@ -2503,6 +2503,7 @@ static CPUArchId *spapr_find_cpu_slot(MachineState *ms, uint32_t id, int *idx) > > static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) > > { > > MachineState *ms = MACHINE(spapr); > > + SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr); > > Error *local_err = NULL; > > bool vsmt_user = !!spapr->vsmt; > > int kvm_smt = kvmppc_smt_threads(); > > @@ -2529,7 +2530,7 @@ static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) > > goto out; > > } > > /* In this case, spapr->vsmt has been set by the command line */ > > - } else { > > + } else if (!smc->smp_threads_vsmt) { > > /* > > * Default VSMT value is tricky, because we need it to be as > > * consistent as possible (for migration), but this requires > > @@ -2538,6 +2539,8 @@ static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) > > * overwhelmingly common case in production systems. > > */ > > spapr->vsmt = MAX(8, smp_threads); > > + } else { > > + spapr->vsmt = smp_threads; > > } > > > > /* KVM: If necessary, set the SMT mode: */ > > @@ -4452,6 +4455,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data) > > smc->irq = &spapr_irq_dual; > > smc->dr_phb_enabled = true; > > smc->linux_pci_probe = true; > > + smc->smp_threads_vsmt = true; > > } > > > > static const TypeInfo spapr_machine_info = { > > @@ -4519,6 +4523,7 @@ static void spapr_machine_4_1_class_options(MachineClass *mc) > > > > spapr_machine_4_2_class_options(mc); > > smc->linux_pci_probe = false; > > + smc->smp_threads_vsmt = false; > > compat_props_add(mc->compat_props, hw_compat_4_1, hw_compat_4_1_len); > > compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat)); > > } > > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h > > index cbd1a4c9f390..2009eb64f9cb 100644 > > --- a/include/hw/ppc/spapr.h > > +++ b/include/hw/ppc/spapr.h > > @@ -122,6 +122,7 @@ struct SpaprMachineClass { > > bool broken_host_serial_model; /* present real host info to the guest */ > > bool pre_4_1_migration; /* don't migrate hpt-max-page-size */ > > bool linux_pci_probe; > > + bool smp_threads_vsmt; /* set VSMT to smp_threads by default */ > > > > void (*phb_placement)(SpaprMachineState *spapr, uint32_t index, > > uint64_t *buid, hwaddr *pio, > > >
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index 8f59f08c102e..473ce1d04775 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -2503,6 +2503,7 @@ static CPUArchId *spapr_find_cpu_slot(MachineState *ms, uint32_t id, int *idx) static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) { MachineState *ms = MACHINE(spapr); + SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr); Error *local_err = NULL; bool vsmt_user = !!spapr->vsmt; int kvm_smt = kvmppc_smt_threads(); @@ -2529,7 +2530,7 @@ static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) goto out; } /* In this case, spapr->vsmt has been set by the command line */ - } else { + } else if (!smc->smp_threads_vsmt) { /* * Default VSMT value is tricky, because we need it to be as * consistent as possible (for migration), but this requires @@ -2538,6 +2539,8 @@ static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp) * overwhelmingly common case in production systems. */ spapr->vsmt = MAX(8, smp_threads); + } else { + spapr->vsmt = smp_threads; } /* KVM: If necessary, set the SMT mode: */ @@ -4452,6 +4455,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data) smc->irq = &spapr_irq_dual; smc->dr_phb_enabled = true; smc->linux_pci_probe = true; + smc->smp_threads_vsmt = true; } static const TypeInfo spapr_machine_info = { @@ -4519,6 +4523,7 @@ static void spapr_machine_4_1_class_options(MachineClass *mc) spapr_machine_4_2_class_options(mc); smc->linux_pci_probe = false; + smc->smp_threads_vsmt = false; compat_props_add(mc->compat_props, hw_compat_4_1, hw_compat_4_1_len); compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat)); } diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h index cbd1a4c9f390..2009eb64f9cb 100644 --- a/include/hw/ppc/spapr.h +++ b/include/hw/ppc/spapr.h @@ -122,6 +122,7 @@ struct SpaprMachineClass { bool broken_host_serial_model; /* present real host info to the guest */ bool pre_4_1_migration; /* don't migrate hpt-max-page-size */ bool linux_pci_probe; + bool smp_threads_vsmt; /* set VSMT to smp_threads by default */ void (*phb_placement)(SpaprMachineState *spapr, uint32_t index, uint64_t *buid, hwaddr *pio,
Support for setting VSMT is available in KVM since linux-4.13. Most distros that support KVM on POWER already have it. It thus seem reasonable enough to have the default machine to set VSMT to smp_threads. This brings contiguous VCPU ids and thus brings their upper bound down to the machine's max_cpus. This is especially useful for XIVE KVM devices, which may thus allocate only one VP descriptor per VCPU. Signed-off-by: Greg Kurz <groug@kaod.org> --- hw/ppc/spapr.c | 7 ++++++- include/hw/ppc/spapr.h | 1 + 2 files changed, 7 insertions(+), 1 deletion(-)