| Message ID | 1368155384-11035-5-git-send-email-scottwood@freescale.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> -----Original Message----- > From: kvm-ppc-owner@vger.kernel.org [mailto:kvm-ppc-owner@vger.kernel.org] On > Behalf Of Scott Wood > Sent: Friday, May 10, 2013 8:40 AM > To: Alexander Graf; Benjamin Herrenschmidt > Cc: kvm-ppc@vger.kernel.org; kvm@vger.kernel.org; linuxppc-dev@lists.ozlabs.org; > Wood Scott-B07421 > Subject: [PATCH v2 4/4] kvm/ppc: IRQ disabling cleanup > > Simplify the handling of lazy EE by going directly from fully-enabled > to hard-disabled. This replaces the lazy_irq_pending() check > (including its misplaced kvm_guest_exit() call). > > As suggested by Tiejun Chen, move the interrupt disabling into > kvmppc_prepare_to_enter() rather than have each caller do it. Also > move the IRQ enabling on heavyweight exit into > kvmppc_prepare_to_enter(). > > Don't move kvmppc_fix_ee_before_entry() into kvmppc_prepare_to_enter(), > so that the caller can avoid marking interrupts enabled earlier than > necessary (e.g. book3s_pr waits until after FP save/restore is done). > > Signed-off-by: Scott Wood <scottwood@freescale.com> > --- > arch/powerpc/include/asm/kvm_ppc.h | 6 ++++++ > arch/powerpc/kvm/book3s_pr.c | 12 +++--------- > arch/powerpc/kvm/booke.c | 9 ++------- > arch/powerpc/kvm/powerpc.c | 21 ++++++++------------- > 4 files changed, 19 insertions(+), 29 deletions(-) > > diff --git a/arch/powerpc/include/asm/kvm_ppc.h > b/arch/powerpc/include/asm/kvm_ppc.h > index 6885846..e4474f8 100644 > --- a/arch/powerpc/include/asm/kvm_ppc.h > +++ b/arch/powerpc/include/asm/kvm_ppc.h > @@ -404,6 +404,12 @@ static inline void kvmppc_fix_ee_before_entry(void) > trace_hardirqs_on(); > > #ifdef CONFIG_PPC64 > + /* > + * To avoid races, the caller must have gone directly from having > + * interrupts fully-enabled to hard-disabled. > + */ > + WARN_ON(local_paca->irq_happened != PACA_IRQ_HARD_DIS); > + > /* Only need to enable IRQs by hard enabling them after this */ > local_paca->irq_happened = 0; > local_paca->soft_enabled = 1; > diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c > index 0b97ce4..e61e39e 100644 > --- a/arch/powerpc/kvm/book3s_pr.c > +++ b/arch/powerpc/kvm/book3s_pr.c > @@ -884,14 +884,11 @@ program_interrupt: > * and if we really did time things so badly, then we just exit > * again due to a host external interrupt. > */ > - local_irq_disable(); > s = kvmppc_prepare_to_enter(vcpu); > - if (s <= 0) { > - local_irq_enable(); > + if (s <= 0) > r = s; > - } else { > + else > kvmppc_fix_ee_before_entry(); > - } > } > > trace_kvm_book3s_reenter(r, vcpu); > @@ -1121,12 +1118,9 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct > kvm_vcpu *vcpu) > * really did time things so badly, then we just exit again due to > * a host external interrupt. > */ > - local_irq_disable(); > ret = kvmppc_prepare_to_enter(vcpu); > - if (ret <= 0) { > - local_irq_enable(); > + if (ret <= 0) > goto out; > - } > > /* Save FPU state in stack */ > if (current->thread.regs->msr & MSR_FP) > diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c > index eb89b83..f7c0111 100644 > --- a/arch/powerpc/kvm/booke.c > +++ b/arch/powerpc/kvm/booke.c > @@ -666,10 +666,8 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct > kvm_vcpu *vcpu) > return -EINVAL; > } > > - local_irq_disable(); > s = kvmppc_prepare_to_enter(vcpu); > if (s <= 0) { > - local_irq_enable(); > ret = s; > goto out; > } > @@ -1148,14 +1146,11 @@ int kvmppc_handle_exit(struct kvm_run *run, struct > kvm_vcpu *vcpu, > * aren't already exiting to userspace for some other reason. > */ > if (!(r & RESUME_HOST)) { > - local_irq_disable(); Ok, Now we do not soft disable before kvmppc_prapare_to_enter(). > s = kvmppc_prepare_to_enter(vcpu); > - if (s <= 0) { > - local_irq_enable(); > + if (s <= 0) > r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV); > - } else { > + else > kvmppc_fix_ee_before_entry(); > - } > } > > return r; > diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c > index 4e05f8c..f8659aa 100644 > --- a/arch/powerpc/kvm/powerpc.c > +++ b/arch/powerpc/kvm/powerpc.c > @@ -64,12 +64,14 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) > { > int r = 1; > > - WARN_ON_ONCE(!irqs_disabled()); > + WARN_ON(irqs_disabled()); > + hard_irq_disable(); Here we hard disable in kvmppc_prepare_to_enter(), so my comment in other patch about interrupt loss is no more valid. So here MSR.EE = 0 local_paca->soft_enabled = 0 local_paca->irq_happened |= PACA_IRQ_HARD_DIS; > + > while (true) { > if (need_resched()) { > local_irq_enable(); This will make the state: MSR.EE = 1 local_paca->soft_enabled = 1 local_paca->irq_happened = PACA_IRQ_HARD_DIS; //same as before Is that a valid state where interrupts are fully enabled and irq_happend in not 0? > cond_resched(); > - local_irq_disable(); > + hard_irq_disable(); > continue; > } > > @@ -95,7 +97,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) > local_irq_enable(); > trace_kvm_check_requests(vcpu); > r = kvmppc_core_check_requests(vcpu); > - local_irq_disable(); > + hard_irq_disable(); > if (r > 0) > continue; > break; > @@ -108,21 +110,14 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) > } > > #ifdef CONFIG_PPC64 > - /* lazy EE magic */ > - hard_irq_disable(); > - if (lazy_irq_pending()) { > - /* Got an interrupt in between, try again */ > - local_irq_enable(); > - local_irq_disable(); > - kvm_guest_exit(); > - continue; > - } > + WARN_ON(lazy_irq_pending()); > #endif > > kvm_guest_enter(); > - break; > + return r; > } > > + local_irq_enable(); > return r; > } int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu) { int r = 0; WARN_ON_ONCE(!irqs_disabled()); kvmppc_core_check_exceptions(vcpu); if (vcpu->requests) { /* Exception delivery raised request; start over */ return 1; } if (vcpu->arch.shared->msr & MSR_WE) { local_irq_enable(); kvm_vcpu_block(vcpu); clear_bit(KVM_REQ_UNHALT, &vcpu->requests); local_irq_disable(); ^^^ We do not require hard_irq_disable() here? -Bharat > #endif /* CONFIG_KVM_BOOK3S_64_HV */ > -- > 1.7.10.4 > > > -- > To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
>> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c >> index 4e05f8c..f8659aa 100644 >> --- a/arch/powerpc/kvm/powerpc.c >> +++ b/arch/powerpc/kvm/powerpc.c >> @@ -64,12 +64,14 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) >> { >> int r = 1; >> >> - WARN_ON_ONCE(!irqs_disabled()); >> + WARN_ON(irqs_disabled()); >> + hard_irq_disable(); > > Here we hard disable in kvmppc_prepare_to_enter(), so my comment in other patch about interrupt loss is no more valid. > > So here > MSR.EE = 0 > local_paca->soft_enabled = 0 > local_paca->irq_happened |= PACA_IRQ_HARD_DIS; > >> + >> while (true) { >> if (need_resched()) { >> local_irq_enable(); > > This will make the state: > MSR.EE = 1 > local_paca->soft_enabled = 1 > local_paca->irq_happened = PACA_IRQ_HARD_DIS; //same as before Why is this same the above state? local_irq_enable() can call __check_irq_replay() to clear PACA_IRQ_HARD_DIS. > > Is that a valid state where interrupts are fully enabled and irq_happend in not 0? > >> cond_resched(); >> - local_irq_disable(); >> + hard_irq_disable(); >> continue; >> } >> >> @@ -95,7 +97,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) >> local_irq_enable(); >> trace_kvm_check_requests(vcpu); >> r = kvmppc_core_check_requests(vcpu); >> - local_irq_disable(); >> + hard_irq_disable(); >> if (r > 0) >> continue; >> break; >> @@ -108,21 +110,14 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) >> } >> >> #ifdef CONFIG_PPC64 >> - /* lazy EE magic */ >> - hard_irq_disable(); >> - if (lazy_irq_pending()) { >> - /* Got an interrupt in between, try again */ >> - local_irq_enable(); >> - local_irq_disable(); >> - kvm_guest_exit(); >> - continue; >> - } >> + WARN_ON(lazy_irq_pending()); >> #endif >> >> kvm_guest_enter(); >> - break; >> + return r; >> } >> >> + local_irq_enable(); >> return r; >> } > > > int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu) > { > int r = 0; > WARN_ON_ONCE(!irqs_disabled()); > > kvmppc_core_check_exceptions(vcpu); > > if (vcpu->requests) { > /* Exception delivery raised request; start over */ > return 1; > } > > if (vcpu->arch.shared->msr & MSR_WE) { > local_irq_enable(); > kvm_vcpu_block(vcpu); > clear_bit(KVM_REQ_UNHALT, &vcpu->requests); > local_irq_disable(); > ^^^ > We do not require hard_irq_disable() here? Between kvmppc_core_prepare_to_enter() and kvmppc_prepare_to_enter(), as I recall Scott had some discussions with Ben earlier. Tiejun > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 05/10/2013 12:01:38 AM, Bhushan Bharat-R65777 wrote: > > > > -----Original Message----- > > From: kvm-ppc-owner@vger.kernel.org > [mailto:kvm-ppc-owner@vger.kernel.org] On > > Behalf Of Scott Wood > > Sent: Friday, May 10, 2013 8:40 AM > > To: Alexander Graf; Benjamin Herrenschmidt > > Cc: kvm-ppc@vger.kernel.org; kvm@vger.kernel.org; > linuxppc-dev@lists.ozlabs.org; > > Wood Scott-B07421 > > Subject: [PATCH v2 4/4] kvm/ppc: IRQ disabling cleanup > > > > - WARN_ON_ONCE(!irqs_disabled()); > > + WARN_ON(irqs_disabled()); > > + hard_irq_disable(); > > Here we hard disable in kvmppc_prepare_to_enter(), so my comment in > other patch about interrupt loss is no more valid. > > So here > MSR.EE = 0 > local_paca->soft_enabled = 0 > local_paca->irq_happened |= PACA_IRQ_HARD_DIS; > > > + > > while (true) { > > if (need_resched()) { > > local_irq_enable(); > > This will make the state: > MSR.EE = 1 > local_paca->soft_enabled = 1 > local_paca->irq_happened = PACA_IRQ_HARD_DIS; //same as before > > Is that a valid state where interrupts are fully enabled and > irq_happend in not 0? PACA_IRQ_HARD_DIS will have been cleared by local_irq_enable(), as Tiejun pointed out. > int kvmppc_core_prepare_to_enter(struct kvm_vcpu *vcpu) > { > int r = 0; > WARN_ON_ONCE(!irqs_disabled()); > > kvmppc_core_check_exceptions(vcpu); > > if (vcpu->requests) { > /* Exception delivery raised request; start over */ > return 1; > } > > if (vcpu->arch.shared->msr & MSR_WE) { > local_irq_enable(); > kvm_vcpu_block(vcpu); > clear_bit(KVM_REQ_UNHALT, &vcpu->requests); > local_irq_disable(); > ^^^ > We do not require hard_irq_disable() here? Yes, that should be changed to hard_irq_disable(), and I'll add a WARN_ON to double check that interrupts are hard-disabled (eventually we'll probably want to make these critical-path assertions dependent on a debug option...). It doesn't really matter all that much, though, since we don't have MSR_WE on any 64-bit booke chips. :-) -Scott -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h index 6885846..e4474f8 100644 --- a/arch/powerpc/include/asm/kvm_ppc.h +++ b/arch/powerpc/include/asm/kvm_ppc.h @@ -404,6 +404,12 @@ static inline void kvmppc_fix_ee_before_entry(void) trace_hardirqs_on(); #ifdef CONFIG_PPC64 + /* + * To avoid races, the caller must have gone directly from having + * interrupts fully-enabled to hard-disabled. + */ + WARN_ON(local_paca->irq_happened != PACA_IRQ_HARD_DIS); + /* Only need to enable IRQs by hard enabling them after this */ local_paca->irq_happened = 0; local_paca->soft_enabled = 1; diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c index 0b97ce4..e61e39e 100644 --- a/arch/powerpc/kvm/book3s_pr.c +++ b/arch/powerpc/kvm/book3s_pr.c @@ -884,14 +884,11 @@ program_interrupt: * and if we really did time things so badly, then we just exit * again due to a host external interrupt. */ - local_irq_disable(); s = kvmppc_prepare_to_enter(vcpu); - if (s <= 0) { - local_irq_enable(); + if (s <= 0) r = s; - } else { + else kvmppc_fix_ee_before_entry(); - } } trace_kvm_book3s_reenter(r, vcpu); @@ -1121,12 +1118,9 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) * really did time things so badly, then we just exit again due to * a host external interrupt. */ - local_irq_disable(); ret = kvmppc_prepare_to_enter(vcpu); - if (ret <= 0) { - local_irq_enable(); + if (ret <= 0) goto out; - } /* Save FPU state in stack */ if (current->thread.regs->msr & MSR_FP) diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c index eb89b83..f7c0111 100644 --- a/arch/powerpc/kvm/booke.c +++ b/arch/powerpc/kvm/booke.c @@ -666,10 +666,8 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) return -EINVAL; } - local_irq_disable(); s = kvmppc_prepare_to_enter(vcpu); if (s <= 0) { - local_irq_enable(); ret = s; goto out; } @@ -1148,14 +1146,11 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu, * aren't already exiting to userspace for some other reason. */ if (!(r & RESUME_HOST)) { - local_irq_disable(); s = kvmppc_prepare_to_enter(vcpu); - if (s <= 0) { - local_irq_enable(); + if (s <= 0) r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV); - } else { + else kvmppc_fix_ee_before_entry(); - } } return r; diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index 4e05f8c..f8659aa 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -64,12 +64,14 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) { int r = 1; - WARN_ON_ONCE(!irqs_disabled()); + WARN_ON(irqs_disabled()); + hard_irq_disable(); + while (true) { if (need_resched()) { local_irq_enable(); cond_resched(); - local_irq_disable(); + hard_irq_disable(); continue; } @@ -95,7 +97,7 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) local_irq_enable(); trace_kvm_check_requests(vcpu); r = kvmppc_core_check_requests(vcpu); - local_irq_disable(); + hard_irq_disable(); if (r > 0) continue; break; @@ -108,21 +110,14 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu) } #ifdef CONFIG_PPC64 - /* lazy EE magic */ - hard_irq_disable(); - if (lazy_irq_pending()) { - /* Got an interrupt in between, try again */ - local_irq_enable(); - local_irq_disable(); - kvm_guest_exit(); - continue; - } + WARN_ON(lazy_irq_pending()); #endif kvm_guest_enter(); - break; + return r; } + local_irq_enable(); return r; } #endif /* CONFIG_KVM_BOOK3S_64_HV */
Simplify the handling of lazy EE by going directly from fully-enabled to hard-disabled. This replaces the lazy_irq_pending() check (including its misplaced kvm_guest_exit() call). As suggested by Tiejun Chen, move the interrupt disabling into kvmppc_prepare_to_enter() rather than have each caller do it. Also move the IRQ enabling on heavyweight exit into kvmppc_prepare_to_enter(). Don't move kvmppc_fix_ee_before_entry() into kvmppc_prepare_to_enter(), so that the caller can avoid marking interrupts enabled earlier than necessary (e.g. book3s_pr waits until after FP save/restore is done). Signed-off-by: Scott Wood <scottwood@freescale.com> --- arch/powerpc/include/asm/kvm_ppc.h | 6 ++++++ arch/powerpc/kvm/book3s_pr.c | 12 +++--------- arch/powerpc/kvm/booke.c | 9 ++------- arch/powerpc/kvm/powerpc.c | 21 ++++++++------------- 4 files changed, 19 insertions(+), 29 deletions(-)