Re: [PATCH] ppc64: Fix possible race with set_pte on a present PTE

On Wed, 26 May 2004, Andrea Arcangeli wrote:

after various searching on the x86 docs I found:

	Whenever a page-directory or page-table entry is changed (including when
	the present flag is set to zero), the operating-system must immediately
	invalidate the corresponding entry in the TLB so that it can be updated
	the next time the entry is referenced.

according to the above we'd need to flush the tlb even in
do_anonymous_page on x86, or am I reading it wrong?

You're reading it wrong.

The "including when the present flag is set to zero" part does not mean 
that the present flag was zero _before_, it means "is being set to zero" 
as in "having been non-zero before that".

Anytime the P flag was clear _before_, we don't need to invalidate, 
because non-present entries are not cached in the TLB.

			Linus
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