> > @@ -305,6 +306,21 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> > ret = page_address(page);
> > if (dma_set_decrypted(dev, ret, size))
> > goto out_free_pages;
> > +#ifdef CONFIG_HAS_IOMEM
> > + /*
> > + * Remap the pages in the unencrypted physical address space
> > + * when dma_unencrypted_base is set (e.g., for Hyper-V AMD
> > + * SEV-SNP isolated guests).
> > + */
> > + if (dma_unencrypted_base) {
> > + phys_addr_t ret_pa = virt_to_phys(ret);
> > +
> > + ret_pa += dma_unencrypted_base;
> > + ret = memremap(ret_pa, size, MEMREMAP_WB);
> > + if (!ret)
> > + goto out_encrypt_pages;
> > + }
> > +#endif
>
>
> So:
>
> this needs to move into dma_set_decrypted, otherwise we don't handle
> the dma_alloc_pages case (never mind that this is pretty unreadable).
>
> Which then again largely duplicates the code in swiotlb. So I think
> what we need here is a low-level helper that does the
> set_memory_decrypted and memremap. I'm not quite sure where it
> should go, but maybe some of the people involved with memory
> encryption might have good ideas. unencrypted_base should go with
> it and then both swiotlb and dma-direct can call it.
Agreed, will look into this more (other people's ideas welcome).
> > + /*
> > + * If dma_unencrypted_base is set, the virtual address returned by
> > + * dma_direct_alloc() is in the vmalloc address range.
> > + */
> > + if (!dma_unencrypted_base && is_vmalloc_addr(cpu_addr)) {
> > vunmap(cpu_addr);
> > } else {
> > if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))
> > arch_dma_clear_uncached(cpu_addr, size);
> > +#ifdef CONFIG_HAS_IOMEM
> > + if (dma_unencrypted_base) {
> > + memunmap(cpu_addr);
> > + /* re-encrypt the pages using the original address */
> > + cpu_addr = page_address(pfn_to_page(PHYS_PFN(
> > + dma_to_phys(dev, dma_addr))));
> > + }
> > +#endif
> > if (dma_set_encrypted(dev, cpu_addr, size))
>
> Same on the unmap side. It might also be worth looking into reordering
> the checks in some form instead o that raw dma_unencrypted_base check
> before the unmap.
Got it.
Thanks,
Andrea
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