On Oct 25, 2021, at 3:52 AM, Peter Zijlstra [off-list ref] wrote:

On Thu, Oct 21, 2021 at 05:21:09AM -0700, Nadav Amit wrote:

quoted

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 448cd01eb3ec..18c3366f8f4d 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h

@@ -1146,6 +1146,14 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,

	}
}
#endif
+
+#define __HAVE_ARCH_PMDP_INVALIDATE_AD
+static inline pmd_t pmdp_invalidate_ad(struct vm_area_struct *vma,
+				       unsigned long address, pmd_t *pmdp)
+{
+	return pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp));

Did this want to be something like:

	pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp));
	if (cpu_feature_enabled(X86_BUG_PTE_LEAK))
		flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
	return old;

instead?

Yes. Of course. Where did my code go to? :(

quoted

+}
+
/*
 * Page table pages are page-aligned.  The lower half of the top
 * level is used for userspace and the top half for the kernel.

quoted

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e5ea5f775d5c..435da011b1a2 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c

@@ -1795,10 +1795,11 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,

	 * The race makes MADV_DONTNEED miss the huge pmd and don't clear it
	 * which may break userspace.
	 *
-	 * pmdp_invalidate() is required to make sure we don't miss
-	 * dirty/young flags set by hardware.
+	 * pmdp_invalidate_ad() is required to make sure we don't miss
+	 * dirty/young flags (which are also known as access/dirty) cannot be
+	 * further modifeid by the hardware.

"modified", I think is the more common spelling.

I tried to start a new trend. I will fix it.

quoted

	 */
-	entry = pmdp_invalidate(vma, addr, pmd);
+	entry = pmdp_invalidate_ad(vma, addr, pmd);

	entry = pmd_modify(entry, newprot);
	if (preserve_write)

diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 4e640baf9794..b0ce6c7391bf 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c

@@ -200,6 +200,14 @@ pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,

}
#endif

+#ifndef __HAVE_ARCH_PMDP_INVALIDATE_AD

/*
* Does this deserve a comment to explain the intended difference vs
* pmdp_invalidate() ?
*/

I will add a comment.