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Date: Mon, 02 Mar 2015 14:20:33 +0000
From: Alex Bennée <alex.bennee@...aro.org>
To: Marc Zyngier <marc.zyngier@....com>
Cc: "kvm\@vger.kernel.org" <kvm@...r.kernel.org>,
"linux-arm-kernel\@lists.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"kvmarm\@lists.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
"christoffer.dall\@linaro.org" <christoffer.dall@...aro.org>,
Gleb Natapov <gleb@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
open list <linux-kernel@...r.kernel.org>,
Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH 3/4] arm/arm64: KVM: Fix migration race in the arch timer
Marc Zyngier <marc.zyngier@....com> writes:
> On 02/03/15 08:50, Alex Bennée wrote:
>>
>> Marc Zyngier <marc.zyngier@....com> writes:
>>
>>> On Wed, 25 Feb 2015 15:36:21 +0000
>>> Alex Bennée <alex.bennee@...aro.org> wrote:
>>>
>>> Alex, Christoffer,
>>>
>> <snip>
>>>
>>> So the first half of the patch looks perfectly OK to me...
>>>
>>>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
>>>> index af6a521..3b4ded2 100644
>>>> --- a/virt/kvm/arm/vgic.c
>>>> +++ b/virt/kvm/arm/vgic.c
>>>> @@ -263,6 +263,13 @@ static int vgic_irq_is_queued(struct kvm_vcpu
>>>> *vcpu, int irq) return vgic_bitmap_get_irq_val(&dist->irq_queued,
>>>> vcpu->vcpu_id, irq); }
>>>>
>>>> +static int vgic_irq_is_active(struct kvm_vcpu *vcpu, int irq)
>>>> +{
>>>> + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>>>> +
>>>> + return vgic_bitmap_get_irq_val(&dist->irq_active,
>>>> vcpu->vcpu_id, irq); +}
>>>> +
>>>> static void vgic_irq_set_queued(struct kvm_vcpu *vcpu, int irq)
>>>> {
>>>> struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>>>> @@ -285,6 +292,13 @@ static void vgic_irq_set_active(struct kvm_vcpu
>>>> *vcpu, int irq) vgic_bitmap_set_irq_val(&dist->irq_active,
>>>> vcpu->vcpu_id, irq, 1); }
>>>>
>>>> +static void vgic_irq_clear_active(struct kvm_vcpu *vcpu, int irq)
>>>> +{
>>>> + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>>>> +
>>>> + vgic_bitmap_set_irq_val(&dist->irq_active, vcpu->vcpu_id,
>>>> irq, 0); +}
>>>> +
>>>> static int vgic_dist_irq_get_level(struct kvm_vcpu *vcpu, int irq)
>>>> {
>>>> struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
>>>> @@ -634,16 +648,12 @@ bool vgic_handle_cfg_reg(u32 *reg, struct
>>>> kvm_exit_mmio *mmio, }
>>>>
>>>> /**
>>>> - * vgic_unqueue_irqs - move pending IRQs from LRs to the distributor
>>>> + * vgic_unqueue_irqs - move pending/active IRQs from LRs to the
>>>> distributor
>>>> * @vgic_cpu: Pointer to the vgic_cpu struct holding the LRs
>>>> *
>>>> - * Move any pending IRQs that have already been assigned to LRs back
>>>> to the
>>>> + * Move any IRQs that have already been assigned to LRs back to the
>>>> * emulated distributor state so that the complete emulated state
>>>> can be read
>>>> * from the main emulation structures without investigating the LRs.
>>>> - *
>>>> - * Note that IRQs in the active state in the LRs get their pending
>>>> state moved
>>>> - * to the distributor but the active state stays in the LRs, because
>>>> we don't
>>>> - * track the active state on the distributor side.
>>>> */
>>>> void vgic_unqueue_irqs(struct kvm_vcpu *vcpu)
>>>> {
>>>> @@ -919,7 +929,7 @@ static int compute_pending_for_cpu(struct
>>>> kvm_vcpu *vcpu)
>>>> /*
>>>> * Update the interrupt state and determine which CPUs have pending
>>>> - * interrupts. Must be called with distributor lock held.
>>>> + * or active interrupts. Must be called with distributor lock held.
>>>> */
>>>> void vgic_update_state(struct kvm *kvm)
>>>> {
>>>> @@ -1036,6 +1046,25 @@ static void vgic_retire_disabled_irqs(struct
>>>> kvm_vcpu *vcpu) }
>>>> }
>>>>
>>>> +static void vgic_queue_irq_to_lr(struct kvm_vcpu *vcpu, int irq,
>>>> + int lr_nr, struct vgic_lr vlr)
>>>> +{
>>>> + if (vgic_irq_is_active(vcpu, irq)) {
>>>> + vlr.state |= LR_STATE_ACTIVE;
>>>> + kvm_debug("Set active, clear distributor: 0x%x\n",
>>>> vlr.state);
>>>> + vgic_irq_clear_active(vcpu, irq);
>>>> + vgic_update_state(vcpu->kvm);
>>>> + } else if (vgic_dist_irq_is_pending(vcpu, irq)) {
>>>> + vlr.state |= LR_STATE_PENDING;
>>>> + kvm_debug("Set pending: 0x%x\n", vlr.state);
>>>> + }
>>>> +
>>>> + if (!vgic_irq_is_edge(vcpu, irq))
>>>> + vlr.state |= LR_EOI_INT;
>>>> +
>>>> + vgic_set_lr(vcpu, lr_nr, vlr);
>>>> +}
>>>> +
>>>> /*
>>>> * Queue an interrupt to a CPU virtual interface. Return true on
>>>> success,
>>>> * or false if it wasn't possible to queue it.
>>>> @@ -1063,8 +1092,7 @@ bool vgic_queue_irq(struct kvm_vcpu *vcpu, u8
>>>> sgi_source_id, int irq) if (vlr.source == sgi_source_id) {
>>>> kvm_debug("LR%d piggyback for IRQ%d\n", lr,
>>>> vlr.irq); BUG_ON(!test_bit(lr, vgic_cpu->lr_used));
>>>> - vlr.state |= LR_STATE_PENDING;
>>>> - vgic_set_lr(vcpu, lr, vlr);
>>>> + vgic_queue_irq_to_lr(vcpu, irq, lr, vlr);
>>>> return true;
>>>> }
>>>> }
>>>> @@ -1081,11 +1109,8 @@ bool vgic_queue_irq(struct kvm_vcpu *vcpu, u8
>>>> sgi_source_id, int irq)
>>>> vlr.irq = irq;
>>>> vlr.source = sgi_source_id;
>>>> - vlr.state = LR_STATE_PENDING;
>>>> - if (!vgic_irq_is_edge(vcpu, irq))
>>>> - vlr.state |= LR_EOI_INT;
>>>> -
>>>> - vgic_set_lr(vcpu, lr, vlr);
>>>> + vlr.state = 0;
>>>> + vgic_queue_irq_to_lr(vcpu, irq, lr, vlr);
>>>>
>>>> return true;
>>>> }
>>>
>>>
>>> ... but this whole vgic rework seems rather out of place, and I can't
>>> really see its connection with the timer. Isn't it logically part of the
>>> previous patch?
>>
>> Probably - I was going to re-factor that code with the original patch
>> but it was on the todo list once we had it working. Christoffer than
>> cleaned it up when he fixed the race hence it being here.
>>
>> Would you like it as a separate patch (between 2 and 3) or just rolled
>> into the previous patch?
>
> In general, I prefer smaller patches (keeps the few brain cells left
> from overheating), so if these changes make sense on their own, please
> post them as a separate patch.
Done, new series re-sent.
>
> Thanks,
>
> M.
--
Alex Bennée
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