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KVM: grow_halt_poll_ns() should never shrink vCPU halt_poll_ns

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grow_halt_poll_ns() have a strange behavior in case
(halt_poll_ns_grow == 0) && (vcpu->halt_poll_ns != 0).

In this case, vcpu->halt_pol_ns will be set to zero.
That results in shrinking instead of growing.

Fix issue by changing grow_halt_poll_ns() to not modify
vcpu->halt_poll_ns in case halt_poll_ns_grow is zero

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Nir Weiner <nir.weiner@oracle.com>
Suggested-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nir Weiner 2019-01-27 12:17:14 +02:00 committed by Paolo Bonzini
parent 8ab3c471ee
commit 7fa08e71b4
2 changed files with 9 additions and 2 deletions
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5
arch/powerpc/kvm/book3s_hv.c
View File

@ -3631,8 +3631,11 @@ static void kvmppc_wait_for_exec(struct kvmppc_vcore *vc,
static void grow_halt_poll_ns(struct kvmppc_vcore *vc)
{
if (!halt_poll_ns_grow)
return;
/* 10us base */
if (vc->halt_poll_ns == 0 && halt_poll_ns_grow)
if (vc->halt_poll_ns == 0)
vc->halt_poll_ns = 10000;
else
vc->halt_poll_ns *= halt_poll_ns_grow;

6
virt/kvm/kvm_main.c
View File

@ -2188,8 +2188,11 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
old = val = vcpu->halt_poll_ns;
grow = READ_ONCE(halt_poll_ns_grow);
if (!grow)
goto out;
/* 10us base */
if (val == 0 && grow)
if (val == 0)
val = 10000;
else
val *= grow;
@ -2198,6 +2201,7 @@ static void grow_halt_poll_ns(struct kvm_vcpu *vcpu)
val = halt_poll_ns;
vcpu->halt_poll_ns = val;
out:
trace_kvm_halt_poll_ns_grow(vcpu->vcpu_id, val, old);
}