Commit 29cb4187 authored by Greg Kurz's avatar Greg Kurz Committed by David Gibson
Browse files

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: default avatarGreg Kurz <groug@kaod.org>
Message-Id: <157010411885.246126.12610015369068227139.stgit@bahia.lan>
Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
parent 06d26eeb

hw/ppc/spapr.c

+6 −1
Original line number Diff line number Diff line
@@ -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));

}

include/hw/ppc/spapr.h

+1 −0
Original line number Diff line number Diff line
@@ -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,