RE: [PATCH 3/8] KVM: Handle device assignment to guests

Han, Weidong
2008-07-17T02:10:11Z

Avi Kivity wrote:
>> +static void kvm_pci_pt_work_fn(struct work_struct *work) +{
>> + struct kvm_pci_pt_dev_list *match;
>> + struct kvm_pci_pt_work *int_work;
>> + int source;
>> + unsigned long flags;
>> + int guest_irq;
>> + int host_irq;
>> +
>> + int_work = container_of(work, struct kvm_pci_pt_work, work); +
>> + source = int_work->source ? KVM_PT_SOURCE_IRQ_ACK :
>> KVM_PT_SOURCE_IRQ; + + /* This is taken to safely inject irq
inside
>> the guest. When + * the interrupt injection (or the ioapic code)
>> uses a + * finer-grained lock, update this
>> + */
>> + mutex_lock(&int_work->kvm->lock);
>> + read_lock_irqsave(&kvm_pci_pt_lock, flags);
>> + match =
kvm_find_pci_pt_dev(&int_work->kvm->arch.pci_pt_dev_head,
>> NULL, + int_work->irq, source);
>> + if (!match) {
>> + printk(KERN_ERR "%s: no matching device assigned to
guest "
>> + "found for irq %d, source = %d!\n",
>> + __func__, int_work->irq, int_work->source);
>> + read_unlock_irqrestore(&kvm_pci_pt_lock, flags); +
goto out;
>> + }
>> + guest_irq = match->pt_dev.guest.irq;
>> + host_irq = match->pt_dev.host.irq;
>> + read_unlock_irqrestore(&kvm_pci_pt_lock, flags);
>> +
>> + if (source == KVM_PT_SOURCE_IRQ)
>> + kvm_set_irq(int_work->kvm, guest_irq, 1);
>> + else {
>> + kvm_set_irq(int_work->kvm, int_work->irq, 0);
>> + enable_irq(host_irq);
>> + }
>> +out:
>> + mutex_unlock(&int_work->kvm->lock);
>> + kvm_put_kvm(int_work->kvm);
>> +}
>>
>> +
>> +/* FIXME: Implement the OR logic needed to make shared interrupts
>> on + * this line behave properly + */
>>
>
> Isn't this a showstopper? There is no easy way for a user to avoid
> sharing, especially as we have only three pci irqs at present.
>

Currently it's not easy to avoid sharing. I think we can support MSI for
assgined device to solve sharing problem.

Randy (Weidong)