From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752843Ab2GSMLV (ORCPT ); Thu, 19 Jul 2012 08:11:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10187 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751810Ab2GSMLQ (ORCPT ); Thu, 19 Jul 2012 08:11:16 -0400 Message-ID: <1342699875.3229.51.camel@ul30vt> Subject: Re: [PATCH] kvm: fix race with level interrupts From: Alex Williamson To: "Michael S. Tsirkin" Cc: Avi Kivity , Marcelo Tosatti , gleb@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 19 Jul 2012 06:11:15 -0600 In-Reply-To: <20120719090730.GA20120@redhat.com> References: <20120718215228.GA13905@redhat.com> <1342650401.2229.224.camel@bling.home> <20120718224948.GB14101@redhat.com> <1342653640.2229.234.camel@bling.home> <20120719090730.GA20120@redhat.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2012-07-19 at 12:07 +0300, Michael S. Tsirkin wrote: > On Wed, Jul 18, 2012 at 05:20:40PM -0600, Alex Williamson wrote: > > On Thu, 2012-07-19 at 01:49 +0300, Michael S. Tsirkin wrote: > > > 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? > > > > Please get off your high horse, this bug has existed for a long time and > > nobody has noticed. __ indicates locking and makes people think twice > > about arbitrarily calling it. Correct naming prevents future bugs, > > which is something you've been riding me on in other areas... > > It's all fine but you already sent two messages about improving coding > style in the same patch. What I really hoped for is a thorough review > that looks at all issues at once, including the functional side as well. > Or maybe style comments is all there is ... we'll see. So you're accusing me of an superfluous review because I noted coding style errors? Very professional. My comments on your rfc should validate the review was thorough. > > > > > +{ > > > > > + /* 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); > > > > > } > > > > > > > > > > > >