Re: [PATCH v2 27/30] vfio-pci/zdev: wire up zPCI IOAT assist support

Pierre Morel
2022-01-19T14:01:33Z

On 1/14/22 21:31, Matthew Rosato wrote:
> Introduce support for VFIO_DEVICE_FEATURE_ZPCI_IOAT, which is a new
> VFIO_DEVICE_FEATURE ioctl. This interface is used to indicate that an
> s390x vfio-pci device wishes to enable/disable zPCI I/O Address
> Translation assistance, allowing the host to perform address translation
> and shadowing.
>

Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>

> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> arch/s390/include/asm/kvm_pci.h | 1 +
> drivers/vfio/pci/vfio_pci_core.c | 2 +
> drivers/vfio/pci/vfio_pci_zdev.c | 63 ++++++++++++++++++++++++++++++++
> include/linux/vfio_pci_core.h | 10 +++++
> include/uapi/linux/vfio.h | 8 ++++
> include/uapi/linux/vfio_zdev.h | 13 +++++++
> 6 files changed, 97 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
> index dbab349a4a75..7b6b6d771026 100644
> --- a/arch/s390/include/asm/kvm_pci.h
> +++ b/arch/s390/include/asm/kvm_pci.h
> @@ -32,6 +32,7 @@ struct kvm_zdev {
> struct zpci_dev *zdev;
> struct kvm *kvm;
> u64 rpcit_count;
> + u64 iota;
> struct kvm_zdev_ioat ioat;
> struct zpci_fib fib;
> struct notifier_block nb;
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index 01658de660bd..709d9ba22a60 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1176,6 +1176,8 @@ long vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int cmd,
> return vfio_pci_zdev_feat_interp(vdev, feature, arg);
> case VFIO_DEVICE_FEATURE_ZPCI_AIF:
> return vfio_pci_zdev_feat_aif(vdev, feature, arg);
> + case VFIO_DEVICE_FEATURE_ZPCI_IOAT:
> + return vfio_pci_zdev_feat_ioat(vdev, feature, arg);
> default:
> return -ENOTTY;
> }
> diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
> index 891cfa016d63..2b169d688937 100644
> --- a/drivers/vfio/pci/vfio_pci_zdev.c
> +++ b/drivers/vfio/pci/vfio_pci_zdev.c
> @@ -302,6 +302,68 @@ int vfio_pci_zdev_feat_aif(struct vfio_pci_core_device *vdev,
> return rc;
> }
>
> +int vfio_pci_zdev_feat_ioat(struct vfio_pci_core_device *vdev,
> + struct vfio_device_feature feature,
> + unsigned long arg)
> +{
> + struct zpci_dev *zdev = to_zpci(vdev->pdev);
> + struct vfio_device_zpci_ioat *data;

NIT: something more explicit than "data" like "ioat_feature" ?

> + struct vfio_device_feature *feat;
> + unsigned long minsz;
> + int size, rc = 0;
> +
> + if (!zdev || !zdev->kzdev)
> + return -EINVAL;
> +
> + /* If PROBE specified, return probe results immediately */
> + if (feature.flags & VFIO_DEVICE_FEATURE_PROBE)
> + return kvm_s390_pci_ioat_probe(zdev);
> +
> + /* GET and SET are mutually exclusive */
> + if ((feature.flags & VFIO_DEVICE_FEATURE_GET) &&
> + (feature.flags & VFIO_DEVICE_FEATURE_SET))
> + return -EINVAL;
> +
> + size = sizeof(*feat) + sizeof(*data);
> + feat = kzalloc(size, GFP_KERNEL);
> + if (!feat)
> + return -ENOMEM;
> +
> + data = (struct vfio_device_zpci_ioat *)&feat->data;
> + minsz = offsetofend(struct vfio_device_feature, flags);
> +
> + if (feature.argsz < minsz + sizeof(*data))
> + return -EINVAL;
> +
> + /* Get the rest of the payload for GET/SET */
> + rc = copy_from_user(data, (void __user *)(arg + minsz),
> + sizeof(*data));
> + if (rc)
> + rc = -EINVAL;
> +
> + if (feature.flags & VFIO_DEVICE_FEATURE_GET) {
> + data->iota = (u64)zdev->kzdev->iota;
> + if (copy_to_user((void __user *)arg, feat, size))
> + rc = -EFAULT;
> + } else if (feature.flags & VFIO_DEVICE_FEATURE_SET) {
> + if (data->iota != 0) {
> + rc = kvm_s390_pci_ioat_enable(zdev, data->iota);
> + if (!rc)
> + zdev->kzdev->iota = data->iota;
> + } else if (zdev->kzdev->iota != 0) {
> + rc = kvm_s390_pci_ioat_disable(zdev);
> + if (!rc)
> + zdev->kzdev->iota = 0;
> + }
> + } else {
> + /* Neither GET nor SET were specified */
> + rc = -EINVAL;
> + }
> +
> + kfree(feat);
> + return rc;
> +}
> +
> static int vfio_pci_zdev_group_notifier(struct notifier_block *nb,
> unsigned long action, void *data)
> {
> @@ -351,6 +413,7 @@ void vfio_pci_zdev_release(struct vfio_pci_core_device *vdev)
> */
> if (zdev->gd != 0) {
> kvm_s390_pci_aif_disable(zdev);
> + kvm_s390_pci_ioat_disable(zdev);
> kvm_s390_pci_interp_disable(zdev);
> }
>
> diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
> index 7ec5e82e7933..f17d761ae14e 100644
> --- a/include/linux/vfio_pci_core.h
> +++ b/include/linux/vfio_pci_core.h
> @@ -204,6 +204,9 @@ int vfio_pci_zdev_feat_interp(struct vfio_pci_core_device *vdev,
> int vfio_pci_zdev_feat_aif(struct vfio_pci_core_device *vdev,
> struct vfio_device_feature feature,
> unsigned long arg);
> +int vfio_pci_zdev_feat_ioat(struct vfio_pci_core_device *vdev,
> + struct vfio_device_feature feature,
> + unsigned long arg);
> void vfio_pci_zdev_open(struct vfio_pci_core_device *vdev);
> void vfio_pci_zdev_release(struct vfio_pci_core_device *vdev);
> #else
> @@ -227,6 +230,13 @@ static inline int vfio_pci_zdev_feat_aif(struct vfio_pci_core_device *vdev,
> return -ENOTTY;
> }
>
> +static inline int vfio_pci_zdev_feat_ioat(struct vfio_pci_core_device *vdev,
> + struct vfio_device_feature feature,
> + unsigned long arg)
> +{
> + return -ENOTTY;
> +}
> +
> static inline void vfio_pci_zdev_open(struct vfio_pci_core_device *vdev)
> {
> }
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index fe3bfd99bf50..32c687388f48 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -1016,6 +1016,14 @@ struct vfio_device_feature {
> */
> #define VFIO_DEVICE_FEATURE_ZPCI_AIF (2)
>
> +/*
> + * Provide support for enabling guest I/O address translation assistance for
> + * zPCI devices. This feature is only valid for s390x PCI devices. Data
> + * provided when setting and getting this feature is further described in
> + * vfio_zdev.h
> + */
> +#define VFIO_DEVICE_FEATURE_ZPCI_IOAT (3)
> +
> /* -------- API for Type1 VFIO IOMMU -------- */
>
> /**
> diff --git a/include/uapi/linux/vfio_zdev.h b/include/uapi/linux/vfio_zdev.h
> index c574e23f9385..1a5229b7bb18 100644
> --- a/include/uapi/linux/vfio_zdev.h
> +++ b/include/uapi/linux/vfio_zdev.h
> @@ -110,4 +110,17 @@ struct vfio_device_zpci_aif {
> __u8 sbo; /* Offset of guest summary bit vector */
> };
>
> +/**
> + * VFIO_DEVICE_FEATURE_ZPCI_IOAT
> + *
> + * This feature is used for enabling guest I/O translation assistance for
> + * passthrough zPCI devices using instruction interpretation. When setting
> + * this feature, the iota specifies a KVM guest I/O translation anchor. When
> + * getting this feature, the most recently set anchor (or 0) is returned in
> + * iota.
> + */
> +struct vfio_device_zpci_ioat {
> + __u64 iota;
> +};
> +
> #endif
>

--
Pierre Morel
IBM Lab Boeblingen