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powerpc/kvm/book3s_hv: Use threads_per_subcore in KVM 

To support split core on POWER8 we need to modify various parts of the
KVM code to use threads_per_subcore instead of threads_per_core. On
systems that do not support split core threads_per_subcore ==
threads_per_core and these changes are a nop.

We use threads_per_subcore as the value reported by KVM_CAP_PPC_SMT.
This communicates to userspace that guests can only be created with
a value of threads_per_core that is less than or equal to the current
threads_per_subcore. This ensures that guests can only be created with a
thread configuration that we are able to run given the current split
core mode.

Although threads_per_subcore can change during the life of the system,
the commit that enables that will ensure that threads_per_subcore does
not change during the life of a KVM VM.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Neuling <mikey@neuling.org>
Acked-by: Alexander Graf <agraf@suse.de>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Michael Ellerman 2014-05-23 18:15:29 +10:00 committed by Benjamin Herrenschmidt
parent 6f5e40a300
commit 3102f7843c
2 changed files with 17 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
arch/powerpc/kvm/book3s_hv.c
View File

@ -1266,7 +1266,7 @@ static struct kvm_vcpu *kvmppc_core_vcpu_create_hv(struct kvm *kvm,
int core;
struct kvmppc_vcore *vcore;
core = id / threads_per_core;
core = id / threads_per_subcore;
if (core >= KVM_MAX_VCORES)
goto out;
@ -1305,7 +1305,7 @@ static struct kvm_vcpu *kvmppc_core_vcpu_create_hv(struct kvm *kvm,
init_waitqueue_head(&vcore->wq);
vcore->preempt_tb = TB_NIL;
vcore->lpcr = kvm->arch.lpcr;
vcore->first_vcpuid = core * threads_per_core;
vcore->first_vcpuid = core * threads_per_subcore;
vcore->kvm = kvm;
}
kvm->arch.vcores[core] = vcore;
@ -1495,16 +1495,19 @@ static void kvmppc_wait_for_nap(struct kvmppc_vcore *vc)
static int on_primary_thread(void)
{
int cpu = smp_processor_id();
int thr = cpu_thread_in_core(cpu);
int thr;
if (thr)
/* Are we on a primary subcore? */
if (cpu_thread_in_subcore(cpu))
return 0;
while (++thr < threads_per_core)
thr = 0;
while (++thr < threads_per_subcore)
if (cpu_online(cpu + thr))
return 0;
/* Grab all hw threads so they can't go into the kernel */
for (thr = 1; thr < threads_per_core; ++thr) {
for (thr = 1; thr < threads_per_subcore; ++thr) {
if (kvmppc_grab_hwthread(cpu + thr)) {
/* Couldn't grab one; let the others go */
do {
@ -1563,15 +1566,18 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
}
/*
* Make sure we are running on thread 0, and that
* secondary threads are offline.
* Make sure we are running on primary threads, and that secondary
* threads are offline. Also check if the number of threads in this
* guest are greater than the current system threads per guest.
*/
if (threads_per_core > 1 && !on_primary_thread()) {
if ((threads_per_core > 1) &&
((vc->num_threads > threads_per_subcore) || !on_primary_thread())) {
list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list)
vcpu->arch.ret = -EBUSY;
goto out;
}
vc->pcpu = smp_processor_id();
list_for_each_entry(vcpu, &vc->runnable_threads, arch.run_list) {
kvmppc_start_thread(vcpu);
@ -1599,7 +1605,7 @@ static void kvmppc_run_core(struct kvmppc_vcore *vc)
/* wait for secondary threads to finish writing their state to memory */
if (vc->nap_count < vc->n_woken)
kvmppc_wait_for_nap(vc);
for (i = 0; i < threads_per_core; ++i)
for (i = 0; i < threads_per_subcore; ++i)
kvmppc_release_hwthread(vc->pcpu + i);
/* prevent other vcpu threads from doing kvmppc_start_thread() now */
vc->vcore_state = VCORE_EXITING;

2
arch/powerpc/kvm/powerpc.c
View File

@ -384,7 +384,7 @@ int kvm_dev_ioctl_check_extension(long ext)
#ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
case KVM_CAP_PPC_SMT:
if (hv_enabled)
r = threads_per_core;
r = threads_per_subcore;
else
r = 0;
break;