On Fri, Jan 10, 2020 at 07:03:04PM +0000, Joao Martins wrote:
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -293,6 +293,15 @@ static inline int pgd_devmap(pgd_t pgd)
> {
> return 0;
> }
> +#endif
> +
> +#ifdef CONFIG_ARCH_HAS_PTE_SPECIAL
> +static inline int pmd_special(pmd_t pmd)
> +{
> + return !!(pmd_flags(pmd) & _PAGE_SPECIAL);
> +}
> +#endif
The ifdef/endif don't make much sense here; x86 does have PTE_SPECIAL,
and this is an x86 header file, so that can be assumed.
> +++ b/mm/gup.c
> @@ -2079,6 +2079,9 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp,
> unsigned long addr,
> return __gup_device_huge_pmd(orig, pmdp, addr, end, pages, nr);
> }
>
> + if (pmd_special(orig))
> + return 0;
Here, you're calling it unconditionally. I think you need a pmd_special()
conditionally defined in include/asm-generic/pgtable.h
+#ifndef CONFIG_ARCH_HAS_PTE_SPECIAL
+static inline bool pmd_special(pmd_t pmd)
+{
+ return false;
+}
+#endif
(oh, and plese use bool instead of int; I know that's different from
pte_special(), but pte_special() predates bool and nobody's done the work
to convert it yet)
> +++ b/mm/huge_memory.c
> @@ -791,6 +791,8 @@ static void insert_pfn_pmd(struct vm_area_struct *vma,
> unsigned long addr,
> entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
> if (pfn_t_devmap(pfn))
> entry = pmd_mkdevmap(entry);
> + else if (pfn_t_special(pfn))
> + entry = pmd_mkspecial(entry);
Again, we'll need a generic one.
> @@ -823,8 +825,7 @@ vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t
> pfn, bool write)
> * but we need to be consistent with PTEs and architectures that
> * can't support a 'special' bit.
> */
> - BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
> - !pfn_t_devmap(pfn));
> + BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)));
Should that rather be ...
+ BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
+ !pfn_t_devmap(pfn) && !pfn_t_special(pfn));
I also think this comment needs adjusting:
/*
* There is no pmd_special() but there may be special pmds, e.g.
* in a direct-access (dax) mapping, so let's just replicate the
* !CONFIG_ARCH_HAS_PTE_SPECIAL case from vm_normal_page() here.
*/
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