On 06/09/2010 07:02 AM, Dave McCracken wrote:
> Recent changes to Linux include code to set new flags in the pte,
> including _PAGE_PAT and _PAGE_PWT. That change conflicts with hugepage
> using the pte macros to set up its pmd entries. This patch resolves
> that problem.
>
Could you explain this a bit more clearly? Why is using __pmd not
working in this case? Is it because the kernel is now setting PAT and
PWT on huge pages? But PAT isn't even the same flag for huge pages...
> An additional fix here is to make sure the _PAGE_PRESENT bit is set
> before hugepages does a mk_pte(), since Xen depends on that bit to
> trigger the pfn->mfn translation.
>
Why is the kernel creating a non-present mapping? If it isn't present,
why does it matter whether we do the pfn->mfn conversion?
J
> Signed-off-by: Dave McCracken <dave.mccracken@xxxxxxxxxx>
>
> --------
>
>
> --- stable-2.6.32.x//arch/x86/include/asm/hugetlb.h 2010-06-04
> 12:19:31.000000000 -0500
> +++ 2.6.32-hfix//arch/x86/include/asm/hugetlb.h 2010-06-08
> 12:23:53.000000000 -0500
> @@ -44,7 +44,7 @@ static inline pte_t huge_ptep_get(pte_t
> static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
> pte_t *ptep, pte_t pte)
> {
> - set_pmd((pmd_t *)ptep, __pmd(pte_val(pte)));
> + set_pmd((pmd_t *)ptep, native_make_pmd(native_pte_val(pte)));
> }
>
> static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
> --- stable-2.6.32.x//mm/hugetlb.c 2010-06-04 12:19:36.000000000 -0500
> +++ 2.6.32-hfix//mm/hugetlb.c 2010-06-07 07:11:34.000000000 -0500
> @@ -1732,12 +1732,14 @@ static pte_t make_huge_pte(struct vm_are
> int writable)
> {
> pte_t entry;
> + pgprot_t pgprot;
>
> + pgprot = __pgprot(pgprot_val(vma->vm_page_prot) | _PAGE_PRESENT);
> if (writable) {
> entry =
> - pte_mkwrite(pte_mkdirty(mk_pte(page, vma->vm_page_prot)));
> + pte_mkwrite(pte_mkdirty(mk_pte(page, pgprot)));
> } else {
> - entry = huge_pte_wrprotect(mk_pte(page, vma->vm_page_prot));
> + entry = huge_pte_wrprotect(mk_pte(page, pgprot));
> }
> entry = pte_mkyoung(entry);
> entry = pte_mkhuge(entry);
>
> _______________________________________________
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> http://lists.xensource.com/xen-devel
>
>
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