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spapr: Set VSMT to smp_threads by default 

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>
Message-Id: <157010411885.246126.12610015369068227139.stgit@bahia.lan>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Greg Kurz 2019-10-03 14:02:00 +02:00 committed by David Gibson
parent 06d26eeb47
commit 29cb418749
2 changed files with 7 additions and 1 deletions
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7
hw/ppc/spapr.c
View File

@ -2496,6 +2496,7 @@ 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();
@ -2522,7 +2523,7 @@ 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
@ -2531,6 +2532,8 @@ 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: */
@ -4438,6 +4441,7 @@ 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 = {
@ -4505,6 +4509,7 @@ 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));
}

1
include/hw/ppc/spapr.h
View File

@ -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,