[RFC PATCH v2 40/58] KVM: arm64: smmu-v3: Add map/unmap pages and iova_to_phys

[Jason Gunthorpe]

On Thu, Dec 12, 2024 at 06:04:04PM +0000, Mostafa Saleh wrote:
> Add map_pages and iova_to_phys HVC code, which
> mainly calls the io-pgtable.
> 
> For unmap_pages, we rely on IO_PGTABLE_QUIRK_UNMAP_INVAL, where the
> driver first calls unmap_pages which invalidate all the pages as
> a typical unmap, issuing all the necessary TLB invalidations.
> Then, we will start a page table with 2 callbacks:
> - visit_leaf: for each unmapped leaf, it would decrement the refcount
>   of the page using __pkvm_host_unuse_dma(), reversing the what IOMMU
>   core does in map.
> - visit_post_table: this would free any invalidated tables as they
>   wouldn't be freed because of the quirk.

I don't know if the timelines will work out, but the pagetable stuff
I'm working on will let you write a much more appropriate
implementation for pkvm's usage than trying to hack it into the
iopgtable code like this.

Even the iommu focused routines I have got now would solve this
problem because they allways spit out a linked list of all the memory
to free after map/unmap and never internally free it..

Jason