From: Zhenzhong Duan <zhenzhong.duan@oracle.com>
To: linux-kernel@vger.kernel.org
Cc: pbonzini@redhat.com, rkrcmar@redhat.com,
rafael.j.wysocki@intel.com, joao.m.martins@oracle.com,
mtosatti@redhat.com, kvm@vger.kernel.org,
linux-pm@vger.kernel.org,
Zhenzhong Duan <zhenzhong.duan@oracle.com>
Subject: [PATCH RESEND v2 4/4] KVM: ensure vCPU halt_poll_us in right scope
Date: Wed, 6 Nov 2019 19:55:02 +0800 [thread overview]
Message-ID: <1573041302-4904-5-git-send-email-zhenzhong.duan@oracle.com> (raw)
In-Reply-To: <1573041302-4904-1-git-send-email-zhenzhong.duan@oracle.com>
As user can adjust halt_poll_ns_grow_start and halt_poll_ns which
leads to vcpu->halt_poll_ns beyond the two boundaries. This patch
ensures vcpu->halt_poll_ns in that scope after growing or shrinking.
If halt_poll_ns_shrink is 0, shrink vcpu->halt_poll_ns to
halt_poll_ns_grow_start instead of 0. To disable poll we can set
halt_poll_ns to 0.
In case user wrongly set halt_poll_ns_grow_start > halt_poll_ns > 0,
halt_poll_ns take precedency and poll time is a fixed value of
halt_poll_ns.
This patch also simplifies branch check based on the guest haltpoll
code.
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
---
virt/kvm/kvm_main.c | 29 +++++++++++++----------------
1 file changed, 13 insertions(+), 16 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 359516b..b4fca66 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2308,9 +2308,15 @@ static void shrink_halt_poll_ns(struct kvm_vcpu *vcpu)
old = val = vcpu->halt_poll_ns;
shrink = READ_ONCE(halt_poll_ns_shrink);
if (shrink == 0)
- val = 0;
- else
+ val = halt_poll_ns_grow_start;
+ else {
val /= shrink;
+ if (val < halt_poll_ns_grow_start)
+ val = halt_poll_ns_grow_start;
+ }
+
+ if (val > halt_poll_ns)
+ val = halt_poll_ns;
vcpu->halt_poll_ns = val;
trace_kvm_halt_poll_ns_shrink(vcpu->vcpu_id, val, old);
@@ -2385,21 +2391,12 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
block_ns = ktime_to_ns(cur) - ktime_to_ns(start);
if (!kvm_arch_no_poll(vcpu)) {
- if (!vcpu_valid_wakeup(vcpu)) {
+ /* we had a long block, shrink polling */
+ if (!vcpu_valid_wakeup(vcpu) || block_ns > halt_poll_ns)
shrink_halt_poll_ns(vcpu);
- } else if (halt_poll_ns) {
- if (block_ns <= vcpu->halt_poll_ns)
- ;
- /* we had a long block, shrink polling */
- else if (vcpu->halt_poll_ns && block_ns > halt_poll_ns)
- shrink_halt_poll_ns(vcpu);
- /* we had a short halt and our poll time is too small */
- else if (vcpu->halt_poll_ns < halt_poll_ns &&
- block_ns < halt_poll_ns)
- grow_halt_poll_ns(vcpu);
- } else {
- vcpu->halt_poll_ns = 0;
- }
+ /* we had a short block and our poll time is too small */
+ else if (block_ns > vcpu->halt_poll_ns)
+ grow_halt_poll_ns(vcpu);
}
trace_kvm_vcpu_wakeup(block_ns, waited, vcpu_valid_wakeup(vcpu));
--
1.8.3.1
prev parent reply other threads:[~2019-11-06 11:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-06 11:54 [PATCH RESEND v2 0/4] misc fixes on halt-poll code for both KVM and guest Zhenzhong Duan
2019-11-06 11:54 ` [PATCH RESEND v2 1/4] cpuidle-haltpoll: ensure grow start value is nonzero Zhenzhong Duan
2019-11-15 10:06 ` Rafael J. Wysocki
2019-11-15 10:16 ` Rafael J. Wysocki
2019-11-15 10:26 ` Rafael J. Wysocki
2019-11-17 9:02 ` Zhenzhong Duan
2019-11-06 11:55 ` [PATCH RESEND v2 2/4] KVM: " Zhenzhong Duan
2019-11-11 20:13 ` Sean Christopherson
2019-11-12 12:19 ` Zhenzhong Duan
2019-11-06 11:55 ` [PATCH RESEND v2 3/4] cpuidle-haltpoll: ensure cpu_halt_poll_us in right scope Zhenzhong Duan
2019-11-15 10:45 ` Rafael J. Wysocki
2019-11-17 8:57 ` Zhenzhong Duan
2019-11-06 11:55 ` Zhenzhong Duan [this message]
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