Re: [PATCHv2 22/29] x86/tdx: Make pages shared in ioremap()

[Thomas Gleixner]

On Mon, Jan 24 2022 at 18:02, Kirill A. Shutemov wrote:

> In TDX guests, guest memory is protected from host access. If a guest
> performs I/O, it needs to explicitly share the I/O memory with the host.
>
> Make all ioremap()ed pages that are not backed by normal memory
> (IORES_DESC_NONE or IORES_DESC_RESERVED) mapped as shared.
>
> Since TDX memory encryption support is similar to AMD SEV architecture,
> reuse the infrastructure from AMD SEV code.
>
> Add tdx_shared_mask() interface to get the TDX guest shared bitmask.
>
> pgprot_decrypted() is used by drivers (i915, virtio_gpu, vfio). Export
> both pgprot_encrypted() and pgprot_decrypted().

How so?

# git grep pgprot_encrypted
arch/x86/include/asm/pgtable.h:#define pgprot_encrypted(prot)   __pgprot(__sme_set(pgprot_val(prot)))
arch/x86/mm/ioremap.c:          prot = pgprot_encrypted(prot);
arch/x86/mm/ioremap.c:  return encrypted_prot ? pgprot_encrypted(prot)
arch/x86/mm/mem_encrypt_amd.c:          protection_map[i] = pgprot_encrypted(protection_map[i]);
arch/x86/mm/pat/set_memory.c:           cpa.mask_clr = pgprot_encrypted(cpa.mask_clr);
arch/x86/platform/efi/quirks.c:                           pgprot_val(pgprot_encrypted(FIXMAP_PAGE_NORMAL)));
fs/proc/vmcore.c:       prot = pgprot_encrypted(prot);
include/linux/pgtable.h:#ifndef pgprot_encrypted
include/linux/pgtable.h:#define pgprot_encrypted(prot)  (prot)

I cannot find any of the above mentioned subsystems in this grep
output. Neither does this patch add any users which require those
exports.

Thanks,

        tglx