[tip:x86/pti] x86/mm: Factor out pageattr _PAGE_GLOBAL setting

2018-04-09 Thread tip-bot for Dave Hansen 
Commit-ID:  d1440b23c922d845ff039f64694a32ff356e89fa
Gitweb: https://git.kernel.org/tip/d1440b23c922d845ff039f64694a32ff356e89fa
Author: Dave Hansen 
AuthorDate: Fri, 6 Apr 2018 13:55:02 -0700
Committer:  Ingo Molnar 
CommitDate: Mon, 9 Apr 2018 18:27:32 +0200

x86/mm: Factor out pageattr _PAGE_GLOBAL setting

The pageattr code has a pattern repeated where it sets _PAGE_GLOBAL
for present PTEs but clears it for non-present PTEs.  The intention
is to keep _PAGE_GLOBAL from getting confused with _PAGE_PROTNONE
since _PAGE_GLOBAL is for present PTEs and _PAGE_PROTNONE is for
non-present

But, this pattern makes no sense.  Effectively, it says, if you use
the pageattr code, always set _PAGE_GLOBAL when _PAGE_PRESENT.
canon_pgprot() will clear it if unsupported (because it masks the
value with __supported_pte_mask) but we *always* set it. Even if
canon_pgprot() did not filter _PAGE_GLOBAL, it would be OK.
_PAGE_GLOBAL is ignored when CR4.PGE=0 by the hardware.

This unconditional setting of _PAGE_GLOBAL is a problem when we have
PTI and non-PTI and we want some areas to have _PAGE_GLOBAL and some
not.

This updated version of the code says:
1. Clear _PAGE_GLOBAL when !_PAGE_PRESENT
2. Never set _PAGE_GLOBAL implicitly
3. Allow _PAGE_GLOBAL to be in cpa.set_mask
4. Allow _PAGE_GLOBAL to be inherited from previous PTE

Signed-off-by: Dave Hansen 
Cc: Andrea Arcangeli 
Cc: Andy Lutomirski 
Cc: Arjan van de Ven 
Cc: Borislav Petkov 
Cc: Dan Williams 
Cc: David Woodhouse 
Cc: Greg Kroah-Hartman 
Cc: Hugh Dickins 
Cc: Josh Poimboeuf 
Cc: Juergen Gross 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Nadav Amit 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux...@kvack.org
Link: http://lkml.kernel.org/r/20180406205502.86e19...@viggo.jf.intel.com
Signed-off-by: Ingo Molnar 
---
 arch/x86/mm/pageattr.c | 66 ++
 1 file changed, 23 insertions(+), 43 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 85cf12219dea..4d369d5c04c5 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -512,6 +512,23 @@ static void __set_pmd_pte(pte_t *kpte, unsigned long 
address, pte_t pte)
 #endif
 }
 
+static pgprot_t pgprot_clear_protnone_bits(pgprot_t prot)
+{
+   /*
+* _PAGE_GLOBAL means "global page" for present PTEs.
+* But, it is also used to indicate _PAGE_PROTNONE
+* for non-present PTEs.
+*
+* This ensures that a _PAGE_GLOBAL PTE going from
+* present to non-present is not confused as
+* _PAGE_PROTNONE.
+*/
+   if (!(pgprot_val(prot) & _PAGE_PRESENT))
+   pgprot_val(prot) &= ~_PAGE_GLOBAL;
+
+   return prot;
+}
+
 static int
 try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
@@ -577,18 +594,11 @@ try_preserve_large_page(pte_t *kpte, unsigned long 
address,
 * different bit positions in the two formats.
 */
req_prot = pgprot_4k_2_large(req_prot);
-
-   /*
-* Set the PSE and GLOBAL flags only if the PRESENT flag is
-* set otherwise pmd_present/pmd_huge will return true even on
-* a non present pmd. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
+   req_prot = pgprot_clear_protnone_bits(req_prot);
if (pgprot_val(req_prot) & _PAGE_PRESENT)
-   pgprot_val(req_prot) |= _PAGE_PSE | _PAGE_GLOBAL;
+   pgprot_val(req_prot) |= _PAGE_PSE;
else
-   pgprot_val(req_prot) &= ~(_PAGE_PSE | _PAGE_GLOBAL);
-
+   pgprot_val(req_prot) &= ~_PAGE_PSE;
req_prot = canon_pgprot(req_prot);
 
/*
@@ -698,16 +708,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, 
unsigned long address,
return 1;
}
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is set
-* otherwise pmd/pte_present will return true even on a non
-* present pmd/pte. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(ref_prot) & _PAGE_PRESENT)
-   pgprot_val(ref_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(ref_prot) &= ~_PAGE_GLOBAL;
+   ref_prot = pgprot_clear_protnone_bits(ref_prot);
 
/*
 * Get the target pfn from the original entry:
@@ -930,18 +931,7 @@ static void populate_pte(struct cpa_data *cpa,
 
pte = pte_offset_kernel(pmd, start);
 
-

[tip:x86/pti] x86/mm: Factor out pageattr _PAGE_GLOBAL setting

2018-04-09 Thread tip-bot for Dave Hansen 
Commit-ID:  d1440b23c922d845ff039f64694a32ff356e89fa
Gitweb: https://git.kernel.org/tip/d1440b23c922d845ff039f64694a32ff356e89fa
Author: Dave Hansen 
AuthorDate: Fri, 6 Apr 2018 13:55:02 -0700
Committer:  Ingo Molnar 
CommitDate: Mon, 9 Apr 2018 18:27:32 +0200

x86/mm: Factor out pageattr _PAGE_GLOBAL setting

The pageattr code has a pattern repeated where it sets _PAGE_GLOBAL
for present PTEs but clears it for non-present PTEs.  The intention
is to keep _PAGE_GLOBAL from getting confused with _PAGE_PROTNONE
since _PAGE_GLOBAL is for present PTEs and _PAGE_PROTNONE is for
non-present

But, this pattern makes no sense.  Effectively, it says, if you use
the pageattr code, always set _PAGE_GLOBAL when _PAGE_PRESENT.
canon_pgprot() will clear it if unsupported (because it masks the
value with __supported_pte_mask) but we *always* set it. Even if
canon_pgprot() did not filter _PAGE_GLOBAL, it would be OK.
_PAGE_GLOBAL is ignored when CR4.PGE=0 by the hardware.

This unconditional setting of _PAGE_GLOBAL is a problem when we have
PTI and non-PTI and we want some areas to have _PAGE_GLOBAL and some
not.

This updated version of the code says:
1. Clear _PAGE_GLOBAL when !_PAGE_PRESENT
2. Never set _PAGE_GLOBAL implicitly
3. Allow _PAGE_GLOBAL to be in cpa.set_mask
4. Allow _PAGE_GLOBAL to be inherited from previous PTE

Signed-off-by: Dave Hansen 
Cc: Andrea Arcangeli 
Cc: Andy Lutomirski 
Cc: Arjan van de Ven 
Cc: Borislav Petkov 
Cc: Dan Williams 
Cc: David Woodhouse 
Cc: Greg Kroah-Hartman 
Cc: Hugh Dickins 
Cc: Josh Poimboeuf 
Cc: Juergen Gross 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Nadav Amit 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: linux...@kvack.org
Link: http://lkml.kernel.org/r/20180406205502.86e19...@viggo.jf.intel.com
Signed-off-by: Ingo Molnar 
---
 arch/x86/mm/pageattr.c | 66 ++
 1 file changed, 23 insertions(+), 43 deletions(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 85cf12219dea..4d369d5c04c5 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -512,6 +512,23 @@ static void __set_pmd_pte(pte_t *kpte, unsigned long 
address, pte_t pte)
 #endif
 }
 
+static pgprot_t pgprot_clear_protnone_bits(pgprot_t prot)
+{
+   /*
+* _PAGE_GLOBAL means "global page" for present PTEs.
+* But, it is also used to indicate _PAGE_PROTNONE
+* for non-present PTEs.
+*
+* This ensures that a _PAGE_GLOBAL PTE going from
+* present to non-present is not confused as
+* _PAGE_PROTNONE.
+*/
+   if (!(pgprot_val(prot) & _PAGE_PRESENT))
+   pgprot_val(prot) &= ~_PAGE_GLOBAL;
+
+   return prot;
+}
+
 static int
 try_preserve_large_page(pte_t *kpte, unsigned long address,
struct cpa_data *cpa)
@@ -577,18 +594,11 @@ try_preserve_large_page(pte_t *kpte, unsigned long 
address,
 * different bit positions in the two formats.
 */
req_prot = pgprot_4k_2_large(req_prot);
-
-   /*
-* Set the PSE and GLOBAL flags only if the PRESENT flag is
-* set otherwise pmd_present/pmd_huge will return true even on
-* a non present pmd. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
+   req_prot = pgprot_clear_protnone_bits(req_prot);
if (pgprot_val(req_prot) & _PAGE_PRESENT)
-   pgprot_val(req_prot) |= _PAGE_PSE | _PAGE_GLOBAL;
+   pgprot_val(req_prot) |= _PAGE_PSE;
else
-   pgprot_val(req_prot) &= ~(_PAGE_PSE | _PAGE_GLOBAL);
-
+   pgprot_val(req_prot) &= ~_PAGE_PSE;
req_prot = canon_pgprot(req_prot);
 
/*
@@ -698,16 +708,7 @@ __split_large_page(struct cpa_data *cpa, pte_t *kpte, 
unsigned long address,
return 1;
}
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is set
-* otherwise pmd/pte_present will return true even on a non
-* present pmd/pte. The canon_pgprot will clear _PAGE_GLOBAL
-* for the ancient hardware that doesn't support it.
-*/
-   if (pgprot_val(ref_prot) & _PAGE_PRESENT)
-   pgprot_val(ref_prot) |= _PAGE_GLOBAL;
-   else
-   pgprot_val(ref_prot) &= ~_PAGE_GLOBAL;
+   ref_prot = pgprot_clear_protnone_bits(ref_prot);
 
/*
 * Get the target pfn from the original entry:
@@ -930,18 +931,7 @@ static void populate_pte(struct cpa_data *cpa,
 
pte = pte_offset_kernel(pmd, start);
 
-   /*
-* Set the GLOBAL flags only if the PRESENT flag is
-* set otherwise pte_present will return true even on
-* a non present pte. The canon_pgprot will clear
-* _PAGE_GLOBAL for the ancient hardware that doesn't
-* support it.
-*/
-   if (pgprot_val(pgprot) & _PAGE_PRESENT)
-   pgprot_val(pgprot) |= _PAGE_GLOBAL;
-   else
-