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    SubjectRe: [patch V3 08/11] x86/mm/cpa: Add sanity check for existing mappings
    On Mon, Sep 17, 2018 at 04:29:14PM +0200, Thomas Gleixner wrote:
    > +static void split_set_pte(struct cpa_data *cpa, pte_t *pte, unsigned long pfn,
    > + pgprot_t ref_prot, unsigned long address,
    > + unsigned long size)
    > +{
    > + unsigned int npg = PFN_DOWN(size);
    > + pgprot_t prot;
    > +
    > + /*
    > + * If try_preserve_large_page() discovered an inconsistent mapping,

    You just renamed that thing.. :-)

    > + * remove the invalid protection in the split mapping.
    > + */
    > + if (!cpa->force_static_prot)
    > + goto set;
    > +
    > + prot = static_protections(ref_prot, address, pfn, npg, CPA_PROTECT);
    > +
    > + if (pgprot_val(prot) == pgprot_val(ref_prot))
    > + goto set;
    > +
    > + /*
    > + * If this is splitting a PMD, fix it up. PUD splits cannot be
    > + * fixed trivially as that would require to rescan the newly
    > + * installed PMD mappings after returning from split_large_page()
    > + * so an eventual further split can allocate the necessary PTE
    > + * pages. Warn for now and revisit it in case this actually
    > + * happens.
    > + */
    > + if (size == PAGE_SIZE)
    > + ref_prot = prot;
    > + else
    > + pr_warn_once("CPA: Cannot fixup static protections for PUD split\n");
    > +set:
    > + set_pte(pte, pfn_pte(pfn, ref_prot));
    > +}

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