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    Subject[PATCH 03/13] x86/mm/pageattr: Use _PAGE_GLOBAL bit for EFI page table mappings
    Date
    From: Sai Praneeth <sai.praneeth.prakhya@intel.com>

    Since EFI page tables can be treated as kernel page tables they should
    be global. All the other page mapping functions in pageattr.c set the
    _PAGE_GLOBAL bit and we want to avoid inconsistencies when we map a page
    in the EFI code paths, for example when that page is split in
    __split_large_page(), etc. It also makes it easier to validate that the
    EFI region mappings have the correct attributes because there are fewer
    differences compared with regular kernel mappings.

    Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@intel.com>
    Cc: Ricardo Neri <ricardo.neri@intel.com>
    Cc: Ravi Shankar <ravi.v.shankar@intel.com>
    Cc: Borislav Petkov <bp@alien8.de>
    Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
    ---
    arch/x86/mm/pageattr.c | 14 ++++++++++++++
    1 file changed, 14 insertions(+)

    diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
    index 632d34d20237..bf312da41a6d 100644
    --- a/arch/x86/mm/pageattr.c
    +++ b/arch/x86/mm/pageattr.c
    @@ -909,6 +909,20 @@ static void populate_pte(struct cpa_data *cpa,

    pte = pte_offset_kernel(pmd, start);

    + /*
    + * Set the GLOBAL flags only if the PRESENT flag is
    + * set otherwise pte_present will return true even on
    + * a non present pte. The canon_pgprot will clear
    + * _PAGE_GLOBAL for the ancient hardware that doesn't
    + * support it.
    + */
    + if (pgprot_val(pgprot) & _PAGE_PRESENT)
    + pgprot_val(pgprot) |= _PAGE_GLOBAL;
    + else
    + pgprot_val(pgprot) &= ~_PAGE_GLOBAL;
    +
    + pgprot = canon_pgprot(pgprot);
    +
    while (num_pages-- && start < end) {
    set_pte(pte, pfn_pte(cpa->pfn, pgprot));

    --
    2.6.2
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