On 04/28/2010 07:08 AM, Dave McCracken wrote:
> Somewhere in the move to the paravirt way of doing things hugepages
> stopped working. This patch fixes hugepages.
>
Looks reasonable. I rewrote the commit comment:
Subject: [PATCH] x86/hugetlb: use set_pmd for huge pte operations
On x86, a huge pte is logically a pte, but structurally a pmd. Among
other issues, pmds and ptes overload some flags for multiple uses (PAT
vs PSE), so it is necessary to know which structural level a pagetable
entry is in order interpret it properly.
When huge pages are used within a paravirtualized system, it is therefore
appropriate to use the pmd set of function to operate on them, so that
the hypervisor can correctly validate the update.
Signed-off-by: Dave McCracken <dave.mccracken@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
Does this look correct?
J
> Signed-off-by: Dave McCracken <dave.mccracken@xxxxxxxxxx>
>
> --------
>
> --- 2.6-xen/arch/x86/include/asm/hugetlb.h 2009-10-29 17:48:21.000000000
> -0500
> +++ 2.6-xen-huge/arch/x86/include/asm/hugetlb.h 2010-04-21
> 09:50:40.000000000 -0500
> @@ -36,16 +36,24 @@ static inline void hugetlb_free_pgd_rang
> free_pgd_range(tlb, addr, end, floor, ceiling);
> }
>
> +static inline pte_t huge_ptep_get(pte_t *ptep)
> +{
> + return *ptep;
> +}
> +
> static inline void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
> pte_t *ptep, pte_t pte)
> {
> - set_pte_at(mm, addr, ptep, pte);
> + set_pmd((pmd_t *)ptep, __pmd(pte_val(pte)));
> }
>
> static inline pte_t huge_ptep_get_and_clear(struct mm_struct *mm,
> unsigned long addr, pte_t *ptep)
> {
> - return ptep_get_and_clear(mm, addr, ptep);
> + pte_t pte = huge_ptep_get(ptep);
> +
> + set_huge_pte_at(mm, addr, ptep, __pte(0));
> + return pte;
> }
>
> static inline void huge_ptep_clear_flush(struct vm_area_struct *vma,
> @@ -66,19 +74,25 @@ static inline pte_t huge_pte_wrprotect(p
> static inline void huge_ptep_set_wrprotect(struct mm_struct *mm,
> unsigned long addr, pte_t *ptep)
> {
> - ptep_set_wrprotect(mm, addr, ptep);
> + pte_t pte = huge_ptep_get(ptep);
> +
> + pte = pte_wrprotect(pte);
> + set_huge_pte_at(mm, addr, ptep, pte);
> }
>
> static inline int huge_ptep_set_access_flags(struct vm_area_struct *vma,
> unsigned long addr, pte_t *ptep,
> pte_t pte, int dirty)
> {
> - return ptep_set_access_flags(vma, addr, ptep, pte, dirty);
> -}
> + pte_t oldpte = huge_ptep_get(ptep);
> + int changed = !pte_same(oldpte, pte);
>
> -static inline pte_t huge_ptep_get(pte_t *ptep)
> -{
> - return *ptep;
> + if (changed && dirty) {
> + set_huge_pte_at(vma->vm_mm, addr, ptep, pte);
> + flush_tlb_page(vma, addr);
> + }
> +
> + return changed;
> }
>
> static inline int arch_prepare_hugepage(struct page *page)
>
>
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