Commit 1a54420a authored Apr 06, 2018 by Dave Hansen Committed by Ingo Molnar Apr 12, 2018

x86/mm: Remove extra filtering in pageattr code



The pageattr code has a mode where it can set or clear PTE bits in
existing PTEs, so the page protections of the *new* PTEs come from
one of two places:

  1. The set/clear masks: cpa->mask_clr / cpa->mask_set
  2. The existing PTE

We filter ->mask_set/clr for supported PTE bits at entry to
__change_page_attr() so we never need to filter them again.

The only other place permissions can come from is an existing PTE
and those already presumably have good bits.  We do not need to filter
them again.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kees Cook <keescook@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nadav Amit <namit@vmware.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180406205511.BC072352@viggo.jf.intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent fb43d6cb

arch/x86/mm/pageattr.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -598,7 +598,6 @@ try_preserve_large_page(pte_t *kpte, unsigned long address,
		req_prot = pgprot_clear_protnone_bits(req_prot);
		if (pgprot_val(req_prot) & _PAGE_PRESENT)
		pgprot_val(req_prot) \|= _PAGE_PSE;
		req_prot = canon_pgprot(req_prot);

		/*
		* old_pfn points to the large page base pfn. So we need
		@@ -718,7 +717,7 @@ __split_large_page(struct cpa_data cpa, pte_t kpte, unsigned long address,
		*/
		pfn = ref_pfn;
		for (i = 0; i < PTRS_PER_PTE; i++, pfn += pfninc)
		set_pte(&pbase[i], pfn_pte(pfn, canon_pgprot(ref_prot)));
		set_pte(&pbase[i], pfn_pte(pfn, ref_prot));

		if (virt_addr_valid(address)) {
		unsigned long pfn = PFN_DOWN(__pa(address));
		@@ -935,7 +934,6 @@ static void populate_pte(struct cpa_data *cpa,
		pte = pte_offset_kernel(pmd, start);

		pgprot = pgprot_clear_protnone_bits(pgprot);
		pgprot = canon_pgprot(pgprot);

		while (num_pages-- && start < end) {
		set_pte(pte, pfn_pte(cpa->pfn, pgprot));
		@@ -1234,7 +1232,7 @@ repeat:
		* after all we're only going to change it's attributes
		* not the memory it points to
		*/
		new_pte = pfn_pte(pfn, canon_pgprot(new_prot));
		new_pte = pfn_pte(pfn, new_prot);
		cpa->pfn = pfn;
		/*
		* Do we really change anything ?

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