[Xen-changelog] [xen stable-4.6] restore p2m_access_t enum order to allow bitmask semantics

[patchbot@xxxxxxx]

commit d0cf28597e25c5c7bb12b33598c7f8e12feeff95
Author:     Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>
AuthorDate: Tue Mar 29 15:14:57 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Mar 29 15:14:57 2016 +0200

    restore p2m_access_t enum order to allow bitmask semantics
    
    Nested hap code assumed implict bitmask semantics of the p2m_access_t
    enum prior to C/S 4c63692d7c38c5ac414fe97f8ef37b66e05abe5c
    
    The change to the enum ordering broke this assumption and caused functional
    problems for the nested hap code. As it may be error prone to audit and find
    all other p2m_access users assuming bitmask semantics, instead restore the
    previous enum order and make it explict that bitmask semantics are to be
    preserved for the read, write and execute access types.
    
    Signed-off-by: Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
    master commit: 61a5cfe15dd90b35850fa7359c5c033a1109289e
    master date: 2016-03-15 12:17:52 +0100
---
 xen/arch/x86/mm/hap/nested_hap.c |  2 +-
 xen/include/xen/p2m-common.h     | 17 +++++++++--------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/mm/hap/nested_hap.c b/xen/arch/x86/mm/hap/nested_hap.c
index 0dbae13..9cee5a0 100644
--- a/xen/arch/x86/mm/hap/nested_hap.c
+++ b/xen/arch/x86/mm/hap/nested_hap.c
@@ -263,7 +263,7 @@ nestedhvm_hap_nested_page_fault(struct vcpu *v, paddr_t 
*L2_gpa,
 
     switch ( p2ma_10 )
     {
-    case p2m_access_rwx ... p2m_access_n:
+    case p2m_access_n ... p2m_access_rwx:
         break;
     case p2m_access_rx2rw:
         p2ma_10 = p2m_access_rx;
diff --git a/xen/include/xen/p2m-common.h b/xen/include/xen/p2m-common.h
index 47c40c7..81d6509 100644
--- a/xen/include/xen/p2m-common.h
+++ b/xen/include/xen/p2m-common.h
@@ -15,14 +15,15 @@
  * default.
  */
 typedef enum {
-    p2m_access_rwx   = 0, /* The default access type when not used. */
-    p2m_access_wx    = 1,
-    p2m_access_rx    = 2,
-    p2m_access_x     = 3,
-    p2m_access_rw    = 4,
-    p2m_access_w     = 5,
-    p2m_access_r     = 6,
-    p2m_access_n     = 7, /* No access allowed. */
+    /* Code uses bottom three bits with bitmask semantics */
+    p2m_access_n     = 0, /* No access allowed. */
+    p2m_access_r     = 1 << 0,
+    p2m_access_w     = 1 << 1,
+    p2m_access_x     = 1 << 2,
+    p2m_access_rw    = p2m_access_r | p2m_access_w,
+    p2m_access_rx    = p2m_access_r | p2m_access_x,
+    p2m_access_wx    = p2m_access_w | p2m_access_x,
+    p2m_access_rwx   = p2m_access_r | p2m_access_w | p2m_access_x,
 
     p2m_access_rx2rw = 8, /* Special: page goes from RX to RW on write */
     p2m_access_n2rwx = 9, /* Special: page goes from N to RWX on access, *
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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