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    SubjectRe: [PATCHv3 07/17] x86/mm: Preserve KeyID on pte_modify() and pgprot_modify()
    On Fri, Jun 15, 2018 at 03:31:57PM +0000, Dave Hansen wrote:
    > On 06/15/2018 08:27 AM, Kirill A. Shutemov wrote:
    > > On Fri, Jun 15, 2018 at 01:43:03PM +0000, Dave Hansen wrote:
    > >> On 06/15/2018 05:57 AM, Kirill A. Shutemov wrote:
    > >>>>> +#define _PAGE_CHG_MASK (PTE_PFN_MASK_MAX | _PAGE_PCD | _PAGE_PWT | \
    > >>>>> _PAGE_SPECIAL | _PAGE_ACCESSED | _PAGE_DIRTY | \
    > >>>>> _PAGE_SOFT_DIRTY)
    > >>>>> #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE)
    > >>>> This makes me a bit nervous. We have some places (here) where we
    > >>>> pretend that the KeyID is part of the paddr and then other places like
    > >>>> pte_pfn() where it's not.
    > >>> Other option is to include KeyID mask into _PAGE_CHG_MASK. But it means
    > >>> _PAGE_CHG_MASK would need to reference *two* variables: physical_mask and
    > >>> mktme_keyid_mask. I mentioned this in the commit message.
    > >>
    > >> Why can't it be one variable with a different name that's populated by
    > >> OR'ing physical_mask and mktme_keyid_mask together?
    > >
    > > My point is that we don't need variables at all here.
    > >
    > > Architecture defines range of bits in PTE used for PFN. MKTME reduces the
    > > number of bits for PFN. PTE_PFN_MASK_MAX represents the original
    > > architectural range, before MKTME stole these bits.
    > >
    > > PTE_PFN_MASK_MAX is constant -- on x86-64 bits 51:12 -- regardless of
    > > MKTME support.
    >
    > Then please just rename the make PTE_<SOMETHING>_MASK where <SOMETHING>
    > includes both the concept of a physical address and a MKTME keyID. Just
    > don't call it a pfn if it is not used in physical addressing.

    I have no idea what such concept should be called. I cannot come with
    anything better than PTE_PFN_MASK_MAX. Do you?

    --
    Kirill A. Shutemov

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