Re: [PATCH v4 1/2] iommu/sva: Tighten SVA bind API with explicit flags

[Jason Gunthorpe]

On Mon, May 10, 2021 at 06:25:07AM -0700, Jacob Pan wrote:

> +/*
> + * The IOMMU_SVA_BIND_SUPERVISOR flag requests a PASID which can be used only
> + * for access to kernel addresses. No IOTLB flushes are automatically done
> + * for kernel mappings; it is valid only for access to the kernel's static
> + * 1:1 mapping of physical memory — not to vmalloc or even module mappings.
> + * A future API addition may permit the use of such ranges, by means of an
> + * explicit IOTLB flush call (akin to the DMA API's unmap method).
> + *
> + * It is unlikely that we will ever hook into flush_tlb_kernel_range() to
> + * do such IOTLB flushes automatically.
> + */
> +#define IOMMU_SVA_BIND_SUPERVISOR       BIT(0)

Huh? That isn't really SVA, can you call it something saner please?

Is it really a PASID that always has all of physical memory mapped
into it? Sounds dangerous. What is it for?

Jason