RE: [RFC v2 1/3] vfio: VFIO_IOMMU_CACHE_INVALIDATE

Tian, Kevin
2019-10-25T09:14:13Z

> From: Liu, Yi L
> Sent: Thursday, October 24, 2019 8:26 PM
>
> From: Liu Yi L <yi.l.liu@linux.intel.com>
>
> When the guest "owns" the stage 1 translation structures, the host
> IOMMU driver has no knowledge of caching structure updates unless
> the guest invalidation requests are trapped and passed down to the
> host.
>
> This patch adds the VFIO_IOMMU_CACHE_INVALIDATE ioctl with aims
> at propagating guest stage1 IOMMU cache invalidations to the host.
>
> Cc: Kevin Tian <kevin.tian@intel.com>
> Signed-off-by: Liu Yi L <yi.l.liu@linux.intel.com>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> ---
> drivers/vfio/vfio_iommu_type1.c | 55
> +++++++++++++++++++++++++++++++++++++++++
> include/uapi/linux/vfio.h | 13 ++++++++++
> 2 files changed, 68 insertions(+)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c
> b/drivers/vfio/vfio_iommu_type1.c
> index 96fddc1d..cd8d3a5 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -124,6 +124,34 @@ struct vfio_regions {
> #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \
> (!list_empty(&iommu->domain_list))
>
> +struct domain_capsule {
> + struct iommu_domain *domain;
> + void *data;
> +};
> +
> +/* iommu->lock must be held */
> +static int
> +vfio_iommu_lookup_dev(struct vfio_iommu *iommu,
> + int (*fn)(struct device *dev, void *data),
> + void *data)

'lookup' usually means find a device and then return. But
the real purpose here is to loop all the devices within this
container and then do something. Does it make more
sense to be vfio_iommu_for_each_dev?

> +{
> + struct domain_capsule dc = {.data = data};
> + struct vfio_domain *d;
> + struct vfio_group *g;
> + int ret = 0;
> +
> + list_for_each_entry(d, &iommu->domain_list, next) {
> + dc.domain = d->domain;
> + list_for_each_entry(g, &d->group_list, next) {
> + ret = iommu_group_for_each_dev(g-
> >iommu_group,
> + &dc, fn);
> + if (ret)
> + break;
> + }
> + }
> + return ret;
> +}
> +
> static int put_pfn(unsigned long pfn, int prot);
>
> /*
> @@ -2211,6 +2239,15 @@ static int vfio_iommu_iova_build_caps(struct
> vfio_iommu *iommu,
> return ret;
> }
>
> +static int vfio_cache_inv_fn(struct device *dev, void *data)
> +{
> + struct domain_capsule *dc = (struct domain_capsule *)data;
> + struct vfio_iommu_type1_cache_invalidate *ustruct =
> + (struct vfio_iommu_type1_cache_invalidate *)dc->data;
> +
> + return iommu_cache_invalidate(dc->domain, dev, &ustruct->info);
> +}
> +
> static long vfio_iommu_type1_ioctl(void *iommu_data,
> unsigned int cmd, unsigned long arg)
> {
> @@ -2315,6 +2352,24 @@ static long vfio_iommu_type1_ioctl(void
> *iommu_data,
>
> return copy_to_user((void __user *)arg, &unmap, minsz) ?
> -EFAULT : 0;
> + } else if (cmd == VFIO_IOMMU_CACHE_INVALIDATE) {
> + struct vfio_iommu_type1_cache_invalidate ustruct;

it's weird to call a variable as struct.

> + int ret;
> +
> + minsz = offsetofend(struct
> vfio_iommu_type1_cache_invalidate,
> + info);
> +
> + if (copy_from_user(&ustruct, (void __user *)arg, minsz))
> + return -EFAULT;
> +
> + if (ustruct.argsz < minsz || ustruct.flags)
> + return -EINVAL;
> +
> + mutex_lock(&iommu->lock);
> + ret = vfio_iommu_lookup_dev(iommu, vfio_cache_inv_fn,
> + &ustruct);
> + mutex_unlock(&iommu->lock);
> + return ret;
> }
>
> return -ENOTTY;
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 9e843a1..ccf60a2 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -794,6 +794,19 @@ struct vfio_iommu_type1_dma_unmap {
> #define VFIO_IOMMU_ENABLE _IO(VFIO_TYPE, VFIO_BASE + 15)
> #define VFIO_IOMMU_DISABLE _IO(VFIO_TYPE, VFIO_BASE + 16)
>
> +/**
> + * VFIO_IOMMU_CACHE_INVALIDATE - _IOWR(VFIO_TYPE, VFIO_BASE +
> 24,
> + * struct vfio_iommu_type1_cache_invalidate)
> + *
> + * Propagate guest IOMMU cache invalidation to the host.

guest or first-level/stage-1? Ideally userspace application may also
bind its own address space as stage-1 one day...

> + */
> +struct vfio_iommu_type1_cache_invalidate {
> + __u32 argsz;
> + __u32 flags;
> + struct iommu_cache_invalidate_info info;
> +};
> +#define VFIO_IOMMU_CACHE_INVALIDATE _IO(VFIO_TYPE, VFIO_BASE
> + 24)
> +
> /* -------- Additional API for SPAPR TCE (Server POWERPC) IOMMU --------
> */
>
> /*
> --
> 2.7.4