From: Sergey Senozhatsky senozhatsky@chromium.org
[ Upstream commit ae232ea460888dc5a8b37e840c553b02521fbf18 ]
grow_halt_poll_ns() ignores values between 0 and halt_poll_ns_grow_start (10000 by default). However, when we shrink halt_poll_ns we may fall way below halt_poll_ns_grow_start and endup with halt_poll_ns values that don't make a lot of sense: like 1 or 9, or 19.
VCPU1 trace (halt_poll_ns_shrink equals 2):
VCPU1 grow 10000 VCPU1 shrink 5000 VCPU1 shrink 2500 VCPU1 shrink 1250 VCPU1 shrink 625 VCPU1 shrink 312 VCPU1 shrink 156 VCPU1 shrink 78 VCPU1 shrink 39 VCPU1 shrink 19 VCPU1 shrink 9 VCPU1 shrink 4
Mirror what grow_halt_poll_ns() does and set halt_poll_ns to 0 as soon as new shrink-ed halt_poll_ns value falls below halt_poll_ns_grow_start.
Signed-off-by: Sergey Senozhatsky senozhatsky@chromium.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Message-Id: 20210902031100.252080-1-senozhatsky@chromium.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- virt/kvm/kvm_main.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index b50dbe269f4b..1a11dcb670a3 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3053,15 +3053,19 @@ out:
static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu) { - unsigned int old, val, shrink; + unsigned int old, val, shrink, grow_start;
old = val = vcpu->halt_poll_ns; shrink = READ_ONCE(halt_poll_ns_shrink); + grow_start = READ_ONCE(halt_poll_ns_grow_start); if (shrink == 0) val = 0; else val /= shrink;
+ if (val < grow_start) + val = 0; + vcpu->halt_poll_ns = val; trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old); }