[PATCH 0/2] Two fixes for dynamic micro-threading

[PATCH 0/2] Two fixes for dynamic micro-threading

[Paul Mackerras]

This series contains two fixes for the new dynamic micro-threading
code that was added recently for HV-mode KVM on Power servers.
The patches are against Alex Graf's kvm-ppc-queue branch.  Please
apply.

Paul.

 arch/powerpc/kvm/book3s_hv.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

[PATCH 1/2] KVM: PPC: Book3S HV: Fix preempted vcore list locking

[Paul Mackerras]

When a vcore gets preempted, we put it on the preempted vcore list for
the current CPU.  The runner task then calls schedule() and comes back
some time later and takes itself off the list.  We need to be careful
to lock the list that it was put onto, which may not be the list for the
current CPU since the runner task may have moved to another CPU.

Signed-off-by: Paul Mackerras <paulus@samba.org>
---
 arch/powerpc/kvm/book3s_hv.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 6e3ef30..3d02276 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -1962,10 +1962,11 @@ static void kvmppc_vcore_preempt(struct kvmppc_vcore *vc)
 
 static void kvmppc_vcore_end_preempt(struct kvmppc_vcore *vc)
 {
-	struct preempted_vcore_list *lp = this_cpu_ptr(&preempted_vcores);
+	struct preempted_vcore_list *lp;
 
 	kvmppc_core_end_stolen(vc);
 	if (!list_empty(&vc->preempt_list)) {
+		lp = &per_cpu(preempted_vcores, vc->pcpu);
 		spin_lock(&lp->lock);
 		list_del_init(&vc->preempt_list);
 		spin_unlock(&lp->lock);
-- 
2.1.4

[PATCH 2/2] KVM: PPC: Book3S HV: Fix preempted vcore stolen time calculation

[Paul Mackerras]

Whenever a vcore state is VCORE_PREEMPT we need to be counting stolen
time for it.  This currently isn't the case when we have a vcore that
no longer has any runnable threads in it but still has a runner task,
so we do an explicit call to kvmppc_core_start_stolen() in that case.

Signed-off-by: Paul Mackerras <paulus@samba.org>
---
 arch/powerpc/kvm/book3s_hv.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 3d02276..fad52f2 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -2283,9 +2283,14 @@ static void post_guest_process(struct kvmppc_vcore *vc, bool is_master)
 	}
 	list_del_init(&vc->preempt_list);
 	if (!is_master) {
-		vc->vcore_state = vc->runner ? VCORE_PREEMPT : VCORE_INACTIVE;
-		if (still_running > 0)
+		if (still_running > 0) {
 			kvmppc_vcore_preempt(vc);
+		} else if (vc->runner) {
+			vc->vcore_state = VCORE_PREEMPT;
+			kvmppc_core_start_stolen(vc);
+		} else {
+			vc->vcore_state = VCORE_INACTIVE;
+		}
 		if (vc->n_runnable > 0 && vc->runner == NULL) {
 			/* make sure there's a candidate runner awake */
 			vcpu = list_first_entry(&vc->runnable_threads,
-- 
2.1.4

Re: [PATCH 0/2] Two fixes for dynamic micro-threading

[Laurent Vivier]

On 16/07/2015 09:11, Paul Mackerras wrote:
> This series contains two fixes for the new dynamic micro-threading
> code that was added recently for HV-mode KVM on Power servers.
> The patches are against Alex Graf's kvm-ppc-queue branch.  Please
> apply.
> 
> Paul.
> 
>  arch/powerpc/kvm/book3s_hv.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)

Tested-by: Laurent Vivier <lvivier@redhat.com>

[this series has corrected a host kernel crash when CPU are overcommitted]

Re: [PATCH 0/2] Two fixes for dynamic micro-threading

[David Gibson]

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On Thu, Jul 16, 2015 at 05:11:12PM +1000, Paul Mackerras wrote:
> This series contains two fixes for the new dynamic micro-threading
> code that was added recently for HV-mode KVM on Power servers.
> The patches are against Alex Graf's kvm-ppc-queue branch.  Please
> apply.

agraf,

Any word on these?  These appear to fix a really nasty host crash in
current upstream.  I'd really like to see them merged ASAP.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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Re: [PATCH 0/2] Two fixes for dynamic micro-threading

[Alexander Graf]

On 20.07.15 08:49, David Gibson wrote:
> On Thu, Jul 16, 2015 at 05:11:12PM +1000, Paul Mackerras wrote:
>> This series contains two fixes for the new dynamic micro-threading
>> code that was added recently for HV-mode KVM on Power servers.
>> The patches are against Alex Graf's kvm-ppc-queue branch.  Please
>> apply.
> 
> agraf,
> 
> Any word on these?  These appear to fix a really nasty host crash in
> current upstream.  I'd really like to see them merged ASAP.

Thanks, applied to kvm-ppc-queue.

The host crash should only occur with dynamic micro-threading enabled,
which is not in Linus' tree, correct?


Alex

Re: [PATCH 0/2] Two fixes for dynamic micro-threading

[Laurent Vivier]

On 23/07/2015 14:02, Alexander Graf wrote:
> 
> 
> On 20.07.15 08:49, David Gibson wrote:
>> On Thu, Jul 16, 2015 at 05:11:12PM +1000, Paul Mackerras wrote:
>>> This series contains two fixes for the new dynamic micro-threading
>>> code that was added recently for HV-mode KVM on Power servers.
>>> The patches are against Alex Graf's kvm-ppc-queue branch.  Please
>>> apply.
>>
>> agraf,
>>
>> Any word on these?  These appear to fix a really nasty host crash in
>> current upstream.  I'd really like to see them merged ASAP.
> 
> Thanks, applied to kvm-ppc-queue.
> 
> The host crash should only occur with dynamic micro-threading enabled,
> which is not in Linus' tree, correct?

Yes, it only occurs with dynamic micro-threading enabled.
Yes, this is not in Linus' tree.

Laurent

Re: [PATCH 0/2] Two fixes for dynamic micro-threading

[Paul Mackerras]

On Thu, Jul 23, 2015 at 02:02:51PM +0200, Alexander Graf wrote:
> 
> The host crash should only occur with dynamic micro-threading enabled,
> which is not in Linus' tree, correct?

Correct.

Paul.