From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from AM1EHSOBE005.bigfish.com (am1ehsobe002.messaging.microsoft.com [213.199.154.205]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (Client CN "mail.global.frontbridge.com", Issuer "Microsoft Secure Server Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id F13711007D9 for ; Sat, 18 Feb 2012 10:00:35 +1100 (EST) Message-ID: <4F3EDC01.5000400@freescale.com> Date: Fri, 17 Feb 2012 17:00:17 -0600 From: Scott Wood MIME-Version: 1.0 To: Alexander Graf Subject: Re: [PATCH 24/30] KVM: PPC: booke: call resched after every exit References: <1329498837-11717-1-git-send-email-agraf@suse.de> <1329498837-11717-25-git-send-email-agraf@suse.de> In-Reply-To: <1329498837-11717-25-git-send-email-agraf@suse.de> Content-Type: text/plain; charset="UTF-8" Cc: linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 02/17/2012 11:13 AM, Alexander Graf wrote: > Instead of checking whether we should reschedule only when we exited > due to an interrupt, let's always check before entering the guest back > again. This gets the target more in line with the other archs. > > Signed-off-by: Alexander Graf > --- > arch/powerpc/kvm/booke.c | 15 ++++++++++----- > 1 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c > index bfb2092..de30b6d 100644 > --- a/arch/powerpc/kvm/booke.c > +++ b/arch/powerpc/kvm/booke.c > @@ -572,6 +572,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu, > unsigned int exit_nr) > { > int r = RESUME_HOST; > + int resched_needed = 1; > > /* update before a new last_exit_type is rewritten */ > kvmppc_update_timing_stats(vcpu); > @@ -602,25 +603,21 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu, > > switch (exit_nr) { > case BOOKE_INTERRUPT_MACHINE_CHECK: > - kvm_resched(vcpu); > r = RESUME_GUEST; > break; > > case BOOKE_INTERRUPT_EXTERNAL: > kvmppc_account_exit(vcpu, EXT_INTR_EXITS); > - kvm_resched(vcpu); > r = RESUME_GUEST; > break; > > case BOOKE_INTERRUPT_DECREMENTER: > kvmppc_account_exit(vcpu, DEC_EXITS); > - kvm_resched(vcpu); > r = RESUME_GUEST; > break; > > case BOOKE_INTERRUPT_DOORBELL: > kvmppc_account_exit(vcpu, DBELL_EXITS); > - kvm_resched(vcpu); > r = RESUME_GUEST; > break; > > @@ -869,8 +866,16 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu, > BUG(); > } > > - local_irq_disable(); > + /* make sure we reschedule if we need to */ > + while (resched_needed) { > + local_irq_disable(); > > + resched_needed = need_resched(); > + if (resched_needed) { > + local_irq_enable(); > + cond_resched(); > + } > + } > kvmppc_core_prepare_to_enter(vcpu); > > if (!(r & RESUME_HOST)) { kvmppc_core_prepare_to_enter can enable interrupts (and block) if guest MSR_WE is set. We may take an interrupt that wants a resched after waking but before interrupts are disabled again. We also want to check for a resched in kvmppc_vcpu_run. So, the resched check belongs in kvmppc_core_prepare_to_enter, something like: /* Check pending exceptions and deliver one, if possible. */ void kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu) { WARN_ON_ONCE(!irqs_disabled()); while (true) { if (signal_pending(current)) break; if (need_resched()) { local_irq_enable(); cond_resched(); local_irq_disable(); continue; } kvmppc_core_check_exceptions(vcpu); if (vcpu->arch.shared->msr & MSR_WE) { local_irq_enable(); kvm_vcpu_block(vcpu); local_irq_disable(); kvmppc_set_exit_type(vcpu, EMULATED_MTMSRWE_EXITS); continue; } break; } } It would be simpler (both here and in the idle hcall) if we could just drop support for CONFIG_PREEMPT=n. :-P -Scott