From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756043Ab2GRWtU (ORCPT ); Wed, 18 Jul 2012 18:49:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:23048 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751491Ab2GRWtP (ORCPT ); Wed, 18 Jul 2012 18:49:15 -0400 Date: Thu, 19 Jul 2012 01:49:48 +0300 From: "Michael S. Tsirkin" To: Alex Williamson Cc: Avi Kivity , Marcelo Tosatti , gleb@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kvm: fix race with level interrupts Message-ID: <20120718224948.GB14101@redhat.com> References: <20120718215228.GA13905@redhat.com> <1342650401.2229.224.camel@bling.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1342650401.2229.224.camel@bling.home> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 18, 2012 at 04:26:41PM -0600, Alex Williamson wrote: > On Thu, 2012-07-19 at 00:52 +0300, Michael S. Tsirkin wrote: > > When more than 1 source id is in use for the same GSI, we have the > > following race related to handling irq_states: > > > > CPU 0 clears bit in irq_states. CPU 0 reads irq_state as 0. > > CPU 1 sets bit in irq_states. CPU 1 calls kvm_ioapic_set_irq(1). CPU 0 > > calls kvm_ioapic_set_irq(0). > > > > Now ioapic thinks the level is 0 but irq_state is not 0. > > > > Note that above is valid behaviour if CPU0 and CPU1 are using different > > source ids. > > > > Fix by performing all irq_states bitmap handling under pic/ioapic lock. > > This also removes the need for atomics with irq_states handling. > > > > Reported-by: Gleb Natapov > > Signed-off-by: Michael S. Tsirkin > > --- > > > > This survives stress testing for me (though I only tried virtio, not > > device assignment). > > Avi, Marcelo, though we have not observed this in the field, > > it's a bugfix so probably 3.5 material? > > I assume yes so the patch is against 3.5-rc7. > > Also stable? It's a very old bug. > > > > > > arch/x86/include/asm/kvm_host.h | 15 ++++++++++++++- > > arch/x86/kvm/i8259.c | 14 ++++++++++++-- > > virt/kvm/ioapic.c | 13 ++++++++++++- > > virt/kvm/ioapic.h | 4 +++- > > virt/kvm/irq_comm.c | 31 ++++--------------------------- > > 5 files changed, 45 insertions(+), 32 deletions(-) > > > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > > index db7c1f2..fe6e9f1 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -802,7 +802,20 @@ int kvm_read_guest_page_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, > > void kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault); > > bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl); > > > > -int kvm_pic_set_irq(void *opaque, int irq, int level); > > +static inline int kvm_irq_line_state(unsigned long *irq_state, > > + int irq_source_id, int level) > > This should probably be __kvm_irq_line_state given the calling > restrictions. It's such a trivial helper, do we need to split hairs about this? Look it's not a good time for minor coding style nits. 3.5 is imminent, it's about 1am here and I really don't have time to retest today, so we'll release another kernel with a bug. Could you focus on reviewing the functionality and correctness, and leave ideas for better variable naming aside until 3.6? > > +{ > > + /* Logical OR for level trig interrupt */ > > + if (level) > > + __set_bit(irq_source_id, irq_state); > > + else > > + __clear_bit(irq_source_id, irq_state); > > + > > + return !!(*irq_state); > > +} > > + > > +int kvm_pic_set_irq(struct kvm_pic *pic, int irq, int irq_source_id, int level); > > +void kvm_pic_clear_all(struct kvm_pic *pic, int irq_source_id); > > > > void kvm_inject_nmi(struct kvm_vcpu *vcpu); > > > > diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c > > index 81cf4fa..95b504b 100644 > > --- a/arch/x86/kvm/i8259.c > > +++ b/arch/x86/kvm/i8259.c > > @@ -188,13 +188,14 @@ void kvm_pic_update_irq(struct kvm_pic *s) > > pic_unlock(s); > > } > > > > -int kvm_pic_set_irq(void *opaque, int irq, int level) > > +int kvm_pic_set_irq(struct kvm_pic *s, int irq, int src_id, int l) > > { > > - struct kvm_pic *s = opaque; > > int ret = -1; > > + int level; > > > > pic_lock(s); > > if (irq >= 0 && irq < PIC_NUM_PINS) { > > + level = kvm_irq_line_state(&s->irq_states[irq], src_id, l); > > ret = pic_set_irq1(&s->pics[irq >> 3], irq & 7, level); > > pic_update_irq(s); > > trace_kvm_pic_set_irq(irq >> 3, irq & 7, s->pics[irq >> 3].elcr, > > @@ -205,6 +206,15 @@ int kvm_pic_set_irq(void *opaque, int irq, int level) > > return ret; > > } > > > > +void kvm_pic_clear_all(struct kvm_pic *s, int src_id) > > +{ > > + int i; > > + pic_lock(s); > > + for (i = 0; i < PIC_NUM_PINS; i++) > > + __clear_bit(src_id, &s->irq_states[i]); > > + pic_unlock(s); > > +} > > + > > /* > > * acknowledge interrupt 'irq' > > */ > > diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c > > index 26fd54d..268b332 100644 > > --- a/virt/kvm/ioapic.c > > +++ b/virt/kvm/ioapic.c > > @@ -191,17 +191,19 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq) > > return kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe); > > } > > > > -int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level) > > +int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int src_id, int l) > > { > > u32 old_irr; > > u32 mask = 1 << irq; > > union kvm_ioapic_redirect_entry entry; > > int ret = 1; > > + int level; > > > > spin_lock(&ioapic->lock); > > old_irr = ioapic->irr; > > if (irq >= 0 && irq < IOAPIC_NUM_PINS) { > > entry = ioapic->redirtbl[irq]; > > + level = kvm_irq_line_state(&ioapic->irq_states[irq], src_id, l); > > level ^= entry.fields.polarity; > > if (!level) > > ioapic->irr &= ~mask; > > @@ -221,6 +223,15 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level) > > return ret; > > } > > > > +void kvm_ioapic_clear_all(struct kvm_ioapic *ioapic, int src_id) > > +{ > > + int i; > > + spin_lock(&ioapic->lock); > > + for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++) > > + __clear_bit(src_id, &ioapic->irq_states[i]); > > + spin_unlock(&ioapic->lock); > > +} > > + > > static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector, > > int trigger_mode) > > { > > diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h > > index 32872a0..a30abfe 100644 > > --- a/virt/kvm/ioapic.h > > +++ b/virt/kvm/ioapic.h > > @@ -74,7 +74,9 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode); > > bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector); > > int kvm_ioapic_init(struct kvm *kvm); > > void kvm_ioapic_destroy(struct kvm *kvm); > > -int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level); > > +int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id, > > + int level); > > +void kvm_ioapic_clear_all(struct kvm_ioapic *ioapic, int irq_source_id); > > void kvm_ioapic_reset(struct kvm_ioapic *ioapic); > > int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src, > > struct kvm_lapic_irq *irq); > > diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c > > index 5afb431..83402d7 100644 > > --- a/virt/kvm/irq_comm.c > > +++ b/virt/kvm/irq_comm.c > > @@ -33,26 +33,12 @@ > > > > #include "ioapic.h" > > > > -static inline int kvm_irq_line_state(unsigned long *irq_state, > > - int irq_source_id, int level) > > -{ > > - /* Logical OR for level trig interrupt */ > > - if (level) > > - set_bit(irq_source_id, irq_state); > > - else > > - clear_bit(irq_source_id, irq_state); > > - > > - return !!(*irq_state); > > -} > > - > > static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e, > > struct kvm *kvm, int irq_source_id, int level) > > { > > #ifdef CONFIG_X86 > > struct kvm_pic *pic = pic_irqchip(kvm); > > - level = kvm_irq_line_state(&pic->irq_states[e->irqchip.pin], > > - irq_source_id, level); > > - return kvm_pic_set_irq(pic, e->irqchip.pin, level); > > + return kvm_pic_set_irq(pic, e->irqchip.pin, irq_source_id, level); > > #else > > return -1; > > #endif > > @@ -62,10 +48,7 @@ static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e, > > struct kvm *kvm, int irq_source_id, int level) > > { > > struct kvm_ioapic *ioapic = kvm->arch.vioapic; > > - level = kvm_irq_line_state(&ioapic->irq_states[e->irqchip.pin], > > - irq_source_id, level); > > - > > - return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, level); > > + return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, irq_source_id, level); > > } > > > > inline static bool kvm_is_dm_lowest_prio(struct kvm_lapic_irq *irq) > > @@ -249,8 +232,6 @@ unlock: > > > > void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id) > > { > > - int i; > > - > > ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID); > > > > mutex_lock(&kvm->irq_lock); > > @@ -263,14 +244,10 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id) > > if (!irqchip_in_kernel(kvm)) > > goto unlock; > > > > - for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++) { > > - clear_bit(irq_source_id, &kvm->arch.vioapic->irq_states[i]); > > - if (i >= 16) > > - continue; > > + kvm_ioapic_clear_all(kvm->arch.vioapic, irq_source_id); > > #ifdef CONFIG_X86 > > - clear_bit(irq_source_id, &pic_irqchip(kvm)->irq_states[i]); > > + kvm_pic_clear_all(pic_irqchip(kvm), irq_source_id); > > #endif > > - } > > unlock: > > mutex_unlock(&kvm->irq_lock); > > } > >