On Fri, 2015-07-10 at 05:57 +0200, Juergen Gross wrote:
> On 07/09/2015 07:03 PM, Toshi Kani wrote:
> > The PAT bit gets relocated to bit 12 when PUD and PMD mappings are
> > used. This bit 12, however, is not covered by PTE_FLAGS_MASK,
> > which
> > is corrently used for masking the flag bits for all cases.
> >
> > Fix pud_flags() and pmd_flags() to cover the PAT bit,
> > _PAGE_PAT_LARGE,
> > when they are used to map a large page with _PAGE_PSE set.
:
> Hmm, I think this covers only half of the problem. pud_pfn() and
> pmd_pfn() will return wrong results for large pages with PAT bit
> set as well.
>
> I'd rather use something like:
>
> static inline unsigned long pmd_pfn_mask(pmd_t pmd)
> {
> if (pmd_large(pmd))
> return PMD_PAGE_MASK & PHYSICAL_PAGE_MASK;
> else
> return PTE_PFN_MASK;
> }
>
> static inline unsigned long pmd_flags_mask(pmd_t pmd)
> {
> if (pmd_large(pmd))
> return ~(PMD_PAGE_MASK & PHYSICAL_PAGE_MASK);
> else
> return ~PTE_PFN_MASK;
> }
>
> static inline unsigned long pmd_pfn(pmd_t pmd)
> {
> return (pmd_val(pmd) & pmd_pfn_mask(pmd)) >> PAGE_SHIFT;
> }
>
> static inline pmdval_t pmd_flags(pmd_t pmd)
> {
> return native_pmd_val(pmd) & ~pmd_flags_mask(pmd);
> }
Thanks for the suggestion! I agree that it is cleaner in this way. I
am updating the patches and found the following changes are needed as
well:
- Define PGTABLE_LEVELS to 2 in
"arch/x86/entry/vdso/vdso32/vclock_gettime.c". This file redefines to
X86_32. Setting to 2 levels (since X86_PAE is not set) allows <asm
-generic/pgtable-nopmd.h> be included to define PMD_SHIFT.
- Move PUD_PAGE_SIZE & PUD_PAGE_MASK from <asm/page_64_types.h> to
<asm/page_types.h>. This allows X86_32 to refer the PUD macros.
- Nit: pmd_large() cannot be used in pmd_xxx_mask() since it calls
pmd_flags(). Use (native_pud_val(pud) & _PAGE_PSE), instead.
Thanks,
-Toshi
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