Messages in this thread Patch in this message | | | From | Anshuman Khandual <> | Subject | [PATCH] x86/mm: Make pud_present() check _PAGE_PROTNONE and _PAGE_PSE as well | Date | Wed, 18 Mar 2020 10:31:19 +0530 |
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pud_present() should also check _PAGE_PROTNONE and _PAGE_PSE bits like in case pmd_present(). This makes a PUD entry test positive for pud_present() after getting invalidated with pud_mknotpresent(), hence standardizing the semantics with PMD helpers.
Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Dave Hansen <dave.hansen@intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: x86@kernel.org Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> --- Even though pud_mknotpresent() is not used any where currently, there is a discrepancy between PMD and PUD.
WARN_ON(!pud_present(pud_mknotpresent(pud_mkhuge(pud)))) -> Fail WARN_ON(!pmd_present(pmd_mknotpresent(pmd_mkhuge(pmd)))) -> Pass
Though pud_mknotpresent() currently clears _PAGE_PROTNONE, pud_present() does not check it. This change fixes both inconsistencies.
This has been build and boot tested on x86.
arch/x86/include/asm/pgtable.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 7e118660bbd9..8adf1d00b506 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -857,7 +857,13 @@ static inline int pud_none(pud_t pud) static inline int pud_present(pud_t pud) { - return pud_flags(pud) & _PAGE_PRESENT; + /* + * Checking for _PAGE_PSE is needed too because + * split_huge_page will temporarily clear the present bit (but + * the _PAGE_PSE flag will remain set at all times while the + * _PAGE_PRESENT bit is clear). + */ + return pud_flags(pud) & (_PAGE_PRESENT | _PAGE_PROTNONE | _PAGE_PSE); } static inline unsigned long pud_page_vaddr(pud_t pud) -- 2.17.1
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