From: Venkatesh Srinivas <venkateshs@chromium.org>
To: Wanpeng Li <kernellwp@gmail.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Ben Segall <bsegall@google.com>,
David Matlack <dmatlack@google.com>,
Paul Mackerras <paulus@ozlabs.org>,
Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Subject: Re: [PATCH v3 1/5] KVM: exit halt polling on need_resched() for both book3s and generic halt-polling
Date: Mon, 17 May 2021 11:13:23 -0700 [thread overview]
Message-ID: <CAA0tLEqeAK76CcyMHkARGFvXsYxLnzm75aUm7bGaoQn939MfvA@mail.gmail.com> (raw)
In-Reply-To: <1621260028-6467-1-git-send-email-wanpengli@tencent.com>
On Mon, May 17, 2021 at 7:01 AM Wanpeng Li <kernellwp@gmail.com> wrote:
>
> From: Wanpeng Li <wanpengli@tencent.com>
>
> Inspired by commit 262de4102c7bb8 (kvm: exit halt polling on need_resched()
> as well), CFS_BANDWIDTH throttling will use resched_task() when there is just
> one task to get the task to block. It was likely allowing VMs to overrun their
> quota when halt polling. Due to PPC implements an arch specific halt polling
> logic, we should add the need_resched() checking there as well. This
> patch adds a helper function that to be shared between book3s and generic
> halt-polling loop.
>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Venkatesh Srinivas <venkateshs@chromium.org>
> Cc: Jim Mattson <jmattson@google.com>
> Cc: David Matlack <dmatlack@google.com>
> Cc: Paul Mackerras <paulus@ozlabs.org>
> Cc: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> v2 -> v3:
> * add a helper function
> v1 -> v2:
> * update patch description
>
> arch/powerpc/kvm/book3s_hv.c | 2 +-
> include/linux/kvm_host.h | 2 ++
> virt/kvm/kvm_main.c | 9 +++++++--
> 3 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index 28a80d240b76..360165df345b 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -3936,7 +3936,7 @@ static void kvmppc_vcore_blocked(struct kvmppc_vcore *vc)
> break;
> }
> cur = ktime_get();
> - } while (single_task_running() && ktime_before(cur, stop));
> + } while (kvm_vcpu_can_block(cur, stop));
>
> spin_lock(&vc->lock);
> vc->vcore_state = VCORE_INACTIVE;
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 2f34487e21f2..bf4fd60c4699 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1583,4 +1583,6 @@ static inline void kvm_handle_signal_exit(struct kvm_vcpu *vcpu)
> /* Max number of entries allowed for each kvm dirty ring */
> #define KVM_DIRTY_RING_MAX_ENTRIES 65536
>
> +bool kvm_vcpu_can_block(ktime_t cur, ktime_t stop);
> +
> #endif
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 6b4feb92dc79..c81080667fd1 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2945,6 +2945,12 @@ update_halt_poll_stats(struct kvm_vcpu *vcpu, u64 poll_ns, bool waited)
> vcpu->stat.halt_poll_success_ns += poll_ns;
> }
>
> +
> +bool kvm_vcpu_can_block(ktime_t cur, ktime_t stop)
> +{
> + return single_task_running() && !need_resched() && ktime_before(cur, stop);
> +}
> +
> /*
> * The vCPU has executed a HLT instruction with in-kernel mode enabled.
> */
> @@ -2973,8 +2979,7 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
> goto out;
> }
> poll_end = cur = ktime_get();
> - } while (single_task_running() && !need_resched() &&
> - ktime_before(cur, stop));
> + } while (kvm_vcpu_can_block(cur, stop));
> }
>
> prepare_to_rcuwait(&vcpu->wait);
> --
> 2.25.1
>
Reviewed-by: Venkatesh Srinivas <venkateshs@chromium.org>
prev parent reply other threads:[~2021-05-17 18:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 14:00 [PATCH v3 1/5] KVM: exit halt polling on need_resched() for both book3s and generic halt-polling Wanpeng Li
2021-05-17 14:00 ` [PATCH v3 2/5] KVM: X86: Bail out of direct yield in case of under-committed scenarios Wanpeng Li
2021-05-17 14:00 ` [PATCH v3 3/5] KVM: X86: Fix vCPU preempted state from guest's point of view Wanpeng Li
2021-05-17 14:00 ` [PATCH v3 4/5] KVM: x86: hyper-v: Task srcu lock when accessing kvm_memslots() Wanpeng Li
2021-05-17 14:00 ` [PATCH v3 5/5] KVM: LAPIC: Narrow the timer latency between wait_lapic_expire and world switch Wanpeng Li
2021-05-17 17:51 ` Sean Christopherson
2021-05-18 12:03 ` Wanpeng Li
2021-05-17 16:34 ` [PATCH v3 1/5] KVM: exit halt polling on need_resched() for both book3s and generic halt-polling David Matlack
2021-05-18 12:03 ` Wanpeng Li
2021-05-17 18:13 ` Venkatesh Srinivas [this message]
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