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SubjectRe: [PATCH v3 13/14] vfio: Document dual stage control
On Wed, Jun 24, 2020 at 01:55:26AM -0700, Liu Yi L wrote:
> +Details can be found in Documentation/userspace-api/iommu.rst. For Intel
> +VT-d, each stage 1 page table is bound to host by:
> +
> + nesting_op->flags = VFIO_IOMMU_NESTING_OP_BIND_PGTBL;
> + memcpy(&nesting_op->data, &bind_data, sizeof(bind_data));
> + ioctl(container->fd, VFIO_IOMMU_NESTING_OP, nesting_op);
> +
> +As mentioned above, guest OS may use stage 1 for GIOVA->GPA or GVA->GPA.
> +GVA->GPA page tables are available when PASID (Process Address Space ID)
> +is exposed to guest. e.g. guest with PASID-capable devices assigned. For
> +such page table binding, the bind_data should include PASID info, which
> +is allocated by guest itself or by host. This depends on hardware vendor
> +e.g. Intel VT-d requires to allocate PASID from host. This requirement is
> +defined by the Virtual Command Support in VT-d 3.0 spec, guest software
> +running on VT-d should allocate PASID from host kernel. To allocate PASID
> +from host, user space should +check the IOMMU_NESTING_FEAT_SYSWIDE_PASID


Reviewed-by: Stefan Hajnoczi <>
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