Re: [v2 18/25] KVM: kvm-vfio: implement the VFIO skeleton for VT-d Posted-Interrupts

[Eric Auger <eric.auger-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>]

Hi Feng,

On 12/03/2014 08:39 AM, Feng Wu wrote:
> This patch adds the kvm-vfio interface for VT-d Posted-Interrrupts.
> When guests updates MSI/MSI-x information for an assigned-device,
update
> QEMU will use KVM_DEV_VFIO_DEVICE_POSTING_IRQ attribute to setup
> IRTE for VT-d PI. This patch implement this IRQ attribute.
s/implement/implements
> 
> Signed-off-by: Feng Wu <feng.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> ---
>  include/linux/kvm_host.h |   19 ++++++++
>  virt/kvm/vfio.c          |  103 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 122 insertions(+), 0 deletions(-)
> 
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 5cd4420..8d06678 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1134,6 +1134,25 @@ static inline int kvm_arch_vfio_set_forward(struct kvm_fwd_irq *fwd_irq,
>  }
>  #endif
>  
> +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_POSTING
> +/*
> + * kvm_arch_vfio_update_pi_irte - set IRTE for Posted-Interrupts
> + *
> + * @kvm: kvm
> + * @host_irq: host irq of the interrupt
> + * @guest_irq: gsi of the interrupt
> + * returns 0 on success, < 0 on failure
> + */
> +int kvm_arch_vfio_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
> +				 uint32_t guest_irq);
> +#else
> +static int kvm_arch_vfio_update_pi_irte(struct kvm *kvm, unsigned int host_irq,
> +					uint32_t guest_irq)
> +{
> +	return 0;
> +}
> +#endif
> +
>  #ifdef CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT
>  
>  static inline void kvm_vcpu_set_in_spin_loop(struct kvm_vcpu *vcpu, bool val)
> diff --git a/virt/kvm/vfio.c b/virt/kvm/vfio.c
> index 6bc7001..5e5515f 100644
> --- a/virt/kvm/vfio.c
> +++ b/virt/kvm/vfio.c
> @@ -446,6 +446,99 @@ out:
>  	return ret;
>  }
>  
> +static int kvm_vfio_pci_get_irq_count(struct pci_dev *pdev, int irq_type)
> +{
> +	if (irq_type == VFIO_PCI_INTX_IRQ_INDEX) {
> +		u8 pin;
> +
> +		pci_read_config_byte(pdev, PCI_INTERRUPT_PIN, &pin);
> +		if (pin)
> +			return 1;
> +	} else if (irq_type == VFIO_PCI_MSI_IRQ_INDEX)
> +		return pci_msi_vec_count(pdev);
> +	else if (irq_type == VFIO_PCI_MSIX_IRQ_INDEX)
> +		return pci_msix_vec_count(pdev);
> +
> +	return 0;
> +}
for platform case I was asked to move the retrieval of absolute irq
number to the architecture specific part. I don't know if it should
apply to PCI stuff as well? This explains why I need to pass the VFIO
device (or struct device handle) to the arch specific part. Actually we
do the same job, we provide a phys/virt IRQ mapping to KVM, right? So to
me our architecture specific API should look quite similar?

> +
> +static int kvm_vfio_set_pi(struct kvm_device *kdev, int32_t __user *argp)
> +{
> +	struct kvm_vfio_dev_irq pi_info;
> +	uint32_t *gsi;
> +	unsigned long minsz;
> +	struct vfio_device *vdev;
> +	struct msi_desc *entry;
> +	struct device *dev;
> +	struct pci_dev *pdev;
> +	int i, max, ret;
> +
> +	minsz = offsetofend(struct kvm_vfio_dev_irq, count);
> +
> +	if (copy_from_user(&pi_info, (void __user *)argp, minsz))
> +		return -EFAULT;
> +
> +	if (pi_info.argsz < minsz || pi_info.index >= VFIO_PCI_NUM_IRQS)
PCI specific check, same remark as above but I will let Alex further
comment on this and possibly invalidate this commeny ;-)
> +		return -EINVAL;
> +
> +	vdev = kvm_vfio_get_vfio_device(pi_info.fd);
> +	if (IS_ERR(vdev))
> +		return PTR_ERR(vdev);
> +
> +	dev = kvm_vfio_external_base_device(vdev);
> +	if (!dev || !dev_is_pci(dev)) {
> +		ret = -EFAULT;
> +		goto put_vfio_device;
> +	}
> +
> +	pdev = to_pci_dev(dev);
> +
> +	max = kvm_vfio_pci_get_irq_count(pdev, pi_info.index);
> +	if (max <= 0) {
> +		ret = -EFAULT;
> +		goto put_vfio_device;
> +	}
> +
> +	if (pi_info.argsz - minsz < pi_info.count * sizeof(int) ||
shouldn' we use the actual datatype?
> +	    pi_info.start >= max || pi_info.start + pi_info.count > max) {
> +		ret = -EINVAL;
> +		goto put_vfio_device;
> +	}
> +
> +	gsi = memdup_user((void __user *)((unsigned long)argp + minsz),
> +			   pi_info.count * sizeof(int));
same question as above
> +	if (IS_ERR(gsi)) {
> +		ret = PTR_ERR(gsi);
> +		goto put_vfio_device;
> +	}
> +
> +#ifdef CONFIG_PCI_MSI
> +	for (i = 0; i < pi_info.count; i++) {
> +		list_for_each_entry(entry, &pdev->msi_list, list) {
> +			if (entry->msi_attrib.entry_nr != pi_info.start+i)
> +				continue;
> +
> +			ret = kvm_arch_vfio_update_pi_irte(kdev->kvm,
> +							   entry->irq,
> +							   gsi[i]);
> +			if (ret) {
> +				ret = -EFAULT;
why -EFAULT? and not propagation of original error code?
you may have posting set for part of the subindexes and unset for rest.
Isn't it an issue?

Best Regards

Eric
> +				goto free_gsi;
> +			}
> +		}
> +	}
> +#endif
> +
> +	ret = 0;
> +
> +free_gsi:
> +	kfree(gsi);
> +
> +put_vfio_device:
> +	kvm_vfio_put_vfio_device(vdev);
> +	return ret;
> +}
> +
>  static int kvm_vfio_set_device(struct kvm_device *kdev, long attr, u64 arg)
>  {
>  	int32_t __user *argp = (int32_t __user *)(unsigned long)arg;
> @@ -456,6 +549,11 @@ static int kvm_vfio_set_device(struct kvm_device *kdev, long attr, u64 arg)
>  	case KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ:
>  		ret = kvm_vfio_control_irq_forward(kdev, attr, argp);
>  		break;
> +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_POSTING
> +	case KVM_DEV_VFIO_DEVICE_POSTING_IRQ:
> +		ret = kvm_vfio_set_pi(kdev, argp);
> +		break;
> +#endif
>  	default:
>  		ret = -ENXIO;
>  	}
> @@ -511,6 +609,11 @@ static int kvm_vfio_has_attr(struct kvm_device *dev,
>  		case KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ:
>  			return 0;
>  #endif
> +#ifdef __KVM_HAVE_ARCH_KVM_VFIO_POSTING
> +		case KVM_DEV_VFIO_DEVICE_POSTING_IRQ:
> +			return 0;
> +#endif
> +
>  		}
>  		break;
>  	}
>