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Message-ID: <495f9106220b87ffa9eaf15fcf39b950628adee1.camel@redhat.com>
Date: Wed, 27 Oct 2021 22:27:22 +0300
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>,
Marc Zyngier <maz@...nel.org>,
Huacai Chen <chenhuacai@...nel.org>,
Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
Paul Mackerras <paulus@...abs.org>,
Anup Patel <anup.patel@....com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Christian Borntraeger <borntraeger@...ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
Paolo Bonzini <pbonzini@...hat.com>
Cc: James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Atish Patra <atish.patra@....com>,
David Hildenbrand <david@...hat.com>,
Cornelia Huck <cohuck@...hat.com>,
Claudio Imbrenda <imbrenda@...ux.ibm.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
linux-mips@...r.kernel.org, kvm@...r.kernel.org,
kvm-ppc@...r.kernel.org, kvm-riscv@...ts.infradead.org,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
David Matlack <dmatlack@...gle.com>,
Oliver Upton <oupton@...gle.com>,
Jing Zhang <jingzhangos@...gle.com>
Subject: Re: [PATCH v2 19/43] KVM: Add helpers to wake/query blocking vCPU
On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
> Add helpers to wake and query a blocking vCPU. In addition to providing
> nice names, the helpers reduce the probability of KVM neglecting to use
> kvm_arch_vcpu_get_wait().
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
> arch/arm64/kvm/arch_timer.c | 3 +--
> arch/arm64/kvm/arm.c | 2 +-
> arch/x86/kvm/lapic.c | 2 +-
> include/linux/kvm_host.h | 14 ++++++++++++++
> virt/kvm/async_pf.c | 2 +-
> virt/kvm/kvm_main.c | 8 ++------
> 6 files changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
> index 7e8396f74010..addd53b6eba6 100644
> --- a/arch/arm64/kvm/arch_timer.c
> +++ b/arch/arm64/kvm/arch_timer.c
> @@ -649,7 +649,6 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
> {
> struct arch_timer_cpu *timer = vcpu_timer(vcpu);
> struct timer_map map;
> - struct rcuwait *wait = kvm_arch_vcpu_get_wait(vcpu);
>
> if (unlikely(!timer->enabled))
> return;
> @@ -672,7 +671,7 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
> if (map.emul_ptimer)
> soft_timer_cancel(&map.emul_ptimer->hrtimer);
>
> - if (rcuwait_active(wait))
> + if (kvm_vcpu_is_blocking(vcpu))
> kvm_timer_blocking(vcpu);
>
> /*
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 268b1e7bf700..9ff0e85a9f16 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -622,7 +622,7 @@ void kvm_arm_resume_guest(struct kvm *kvm)
>
> kvm_for_each_vcpu(i, vcpu, kvm) {
> vcpu->arch.pause = false;
> - rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu));
> + __kvm_vcpu_wake_up(vcpu);
> }
> }
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 76fb00921203..0cd7ed21b205 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -1931,7 +1931,7 @@ void kvm_lapic_expired_hv_timer(struct kvm_vcpu *vcpu)
> /* If the preempt notifier has already run, it also called apic_timer_expired */
> if (!apic->lapic_timer.hv_timer_in_use)
> goto out;
> - WARN_ON(rcuwait_active(&vcpu->wait));
> + WARN_ON(kvm_vcpu_is_blocking(vcpu));
> apic_timer_expired(apic, false);
> cancel_hv_timer(apic);
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index bdaa0e70b060..1fa38dc00b87 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1151,6 +1151,20 @@ static inline struct rcuwait *kvm_arch_vcpu_get_wait(struct kvm_vcpu *vcpu)
> #endif
> }
>
> +/*
> + * Wake a vCPU if necessary, but don't do any stats/metadata updates. Returns
> + * true if the vCPU was blocking and was awakened, false otherwise.
> + */
> +static inline bool __kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
> +{
> + return !!rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu));
> +}
> +
> +static inline bool kvm_vcpu_is_blocking(struct kvm_vcpu *vcpu)
> +{
> + return rcuwait_active(kvm_arch_vcpu_get_wait(vcpu));
> +}
> +
> #ifdef __KVM_HAVE_ARCH_INTC_INITIALIZED
> /*
> * returns true if the virtual interrupt controller is initialized and
> diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c
> index ccb35c22785e..9bfe1d6f6529 100644
> --- a/virt/kvm/async_pf.c
> +++ b/virt/kvm/async_pf.c
> @@ -85,7 +85,7 @@ static void async_pf_execute(struct work_struct *work)
>
> trace_kvm_async_pf_completed(addr, cr2_or_gpa);
>
> - rcuwait_wake_up(kvm_arch_vcpu_get_wait(vcpu));
> + __kvm_vcpu_wake_up(vcpu);
>
> mmput(mm);
> kvm_put_kvm(vcpu->kvm);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 481e8178b43d..c870cae7e776 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3332,10 +3332,7 @@ EXPORT_SYMBOL_GPL(kvm_vcpu_halt);
>
> bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
> {
> - struct rcuwait *waitp;
> -
> - waitp = kvm_arch_vcpu_get_wait(vcpu);
> - if (rcuwait_wake_up(waitp)) {
> + if (__kvm_vcpu_wake_up(vcpu)) {
> WRITE_ONCE(vcpu->ready, true);
> ++vcpu->stat.generic.halt_wakeup;
> return true;
> @@ -3490,8 +3487,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode)
> continue;
> if (vcpu == me)
> continue;
> - if (rcuwait_active(kvm_arch_vcpu_get_wait(vcpu)) &&
> - !vcpu_dy_runnable(vcpu))
> + if (kvm_vcpu_is_blocking(vcpu) && !vcpu_dy_runnable(vcpu))
> continue;
> if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode &&
> !kvm_arch_dy_has_pending_interrupt(vcpu) &&
Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>
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