On Mon, Sep 11, 2023 at 08:34:57AM -0700, Dave Hansen wrote:
> On 9/11/23 06:26, Matthew Wilcox wrote:
> > @@ -231,7 +235,10 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
> > if (--nr == 0)
> > break;
> > ptep++;
> > - pte = __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
> > + if (__pte_needs_invert(pte_val(pte)))
> > + pte = __pte(pte_val(pte) - (1UL << PFN_PTE_SHIFT));
> > + else
> > + pte = __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
> > }
> > arch_leave_lazy_mmu_mode();
> > }
>
> This is much better than a whole x86 fork of set_ptes(). But it's still
> a bit wonky because it exposes the PTE inversion logic to generic code.
I saw that as an advantage ... let people know that it exists as a
concept.
> static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
> pte_t *ptep, pte_t pte, unsigned int nr)
> {
> pgprot_t prot = pte_pgprot(x);
> unsigned long pfn = pte_pfn(pte);
>
> page_table_check_ptes_set(mm, ptep, pte, nr);
>
> arch_enter_lazy_mmu_mode();
> for (;;) {
> set_pte(ptep, pte);
> if (--nr == 0)
> break;
> ptep++;
> pfn++;
> pte = pfn_pte(pfn, pgprot);
> }
> arch_leave_lazy_mmu_mode();
> }
>
> Obviously completely untested. :)
After fixing your two typos, this assembles to 176 bytes more code than
my version. Not sure that's great.
How about this? Keeps the inverted knowledge entirely in arch/x86.
Compiles to exactly the same code as the version I sent earlier.
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index d6ad98ca1288..c9781b8b14af 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -955,6 +955,14 @@ static inline int pte_same(pte_t a, pte_t b)
return a.pte == b.pte;
}
+static inline pte_t pte_next(pte_t pte)
+{
+ if (__pte_needs_invert(pte_val(pte)))
+ return __pte(pte_val(pte) - (1UL << PFN_PTE_SHIFT));
+ return __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
+}
+#define pte_next pte_next
+
static inline int pte_present(pte_t a)
{
return pte_flags(a) & (_PAGE_PRESENT | _PAGE_PROTNONE);
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 1fba072b3dac..7a932ed59c27 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -205,6 +205,10 @@ static inline int pmd_young(pmd_t pmd)
#define arch_flush_lazy_mmu_mode() do {} while (0)
#endif
+#ifndef pte_next
+#define pte_next(pte) ((pte) + (1UL << PFN_PTE_SHIFT))
+#endif
+
#ifndef set_ptes
/**
* set_ptes - Map consecutive pages to a contiguous range of addresses.
@@ -231,7 +235,7 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
if (--nr == 0)
break;
ptep++;
- pte = __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT));
+ pte = pte_next(pte);
}
arch_leave_lazy_mmu_mode();
}
