On Mon, Sep 02, 2024 at 06:22:00PM +1000, Alexey Kardashevskiy wrote: > On 24/8/24 08:37, Bjorn Helgaas wrote: > > On Fri, Aug 23, 2024 at 11:21:34PM +1000, Alexey Kardashevskiy wrote: > > > Add another resource#d_enc to allow mapping MMIO as > > > an encrypted/private region. > > > > > > Unlike resourceN_wc, the node is added always as ability to > > > map MMIO as private depends on negotiation with the TSM which > > > happens quite late. > > > @@ -46,6 +46,15 @@ int pci_mmap_resource_range(struct pci_dev *pdev, int bar, > > > vma->vm_ops = &pci_phys_vm_ops; > > > + /* > > > + * Calling remap_pfn_range() directly as io_remap_pfn_range() > > > + * enforces shared mapping. > > > > s/Calling/Call/ > > > > Needs some additional context about why io_remap_pfn_range() can't be > > used here. > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f8f6ae5d077a9bdaf5cbf2ac960a5d1a04b47482 > added this. > > "IO devices do not understand encryption, so this memory must always be > decrypted" it says. Thanks for the pointer. Given that hint, the pgprot_decrypted() inside io_remap_pfn_range() is ... at least *there*, if not obvious. io_remap_pfn_range() probably could benefit from a simple comment to highlight that. > But devices do understand encryption so forcing decryption is not wanted. > What additional context is missing here, that "shared" means > "non-encrypted"? Thanks, If "shared" means "non-encrypted", that would be useful. That wasn't obvious to me. IIUC, in the "enc" case, you *want* the mapping to remain encrypted? In that case, it would be helpful to say something like "io_remap_pfn_range() always produces decrypted mappings, so use remap_pfn_range() directly to avoid the decryption". Renaming "enc" to "encrypted" would also be a nice hint. > > > + */ > > > + if (enc) > > > + return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff, > > > + vma->vm_end - vma->vm_start, > > > + vma->vm_page_prot); > > > + > > > return io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff, > > > vma->vm_end - vma->vm_start, > > > vma->vm_page_prot); > > -- > Alexey >
