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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id x10sm9233166edd.30.2021.05.24.06.46.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 May 2021 06:46:44 -0700 (PDT) Subject: Re: [PATCH v4 1/5] KVM: exit halt polling on need_resched() for both book3s and generic halt-polling To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Ben Segall , Venkatesh Srinivas , David Matlack , Paul Mackerras , Suraj Jitindar Singh References: <1621339235-11131-1-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Message-ID: Date: Mon, 24 May 2021 15:46:43 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <1621339235-11131-1-git-send-email-wanpengli@tencent.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/05/21 14:00, Wanpeng Li wrote: > From: Wanpeng Li > > 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. > > Reviewed-by: David Matlack > Reviewed-by: Venkatesh Srinivas > Cc: Ben Segall > Cc: Venkatesh Srinivas > Cc: Jim Mattson > Cc: David Matlack > Cc: Paul Mackerras > Cc: Suraj Jitindar Singh > Signed-off-by: Wanpeng Li > --- > v3 -> v4: > * rename to kvm_vcpu_can_poll > 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 | 8 ++++++-- > 3 files changed, 9 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c > index 28a80d240b76..7360350e66ff 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_poll(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..ba682f738a25 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_poll(ktime_t cur, ktime_t stop); > + > #endif > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 6b4feb92dc79..62522c12beba 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2945,6 +2945,11 @@ 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_poll(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 +2978,7 @@ 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_poll(cur, stop)); > } > > prepare_to_rcuwait(&vcpu->wait); > Queued all five, thanks. Paolo