Make the PRESENT bit a higher order bit so that it isn't toggled on every
iteration, which is a wee bit problematic when trying to expose bugs in
KVM's TLB flushing since a fault is architecturally guaranteed to flush
TLB entries for the faulting virtual address.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
x86/access.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/x86/access.c b/x86/access.c
index c4db368..24ddeec 100644
--- a/x86/access.c
+++ b/x86/access.c
@@ -37,26 +37,30 @@ static int invalid_mask;
(((address) >> (12 + ((level)-1) * 9)) & 511)
/*
- * page table access check tests
+ * Page table access check tests. Each number/bit represent an individual
+ * test case. The main test will bump a counter by 1 to run all permutations
+ * of the below test cases (sans illegal combinations).
+ *
+ * Keep the PRESENT and reserved bits in the higher numbers so that they aren't
+ * toggled on every test, e.g. to keep entries in the TLB.
*/
-
enum {
- AC_PTE_PRESENT_BIT,
AC_PTE_WRITABLE_BIT,
AC_PTE_USER_BIT,
AC_PTE_ACCESSED_BIT,
AC_PTE_DIRTY_BIT,
AC_PTE_NX_BIT,
+ AC_PTE_PRESENT_BIT,
AC_PTE_BIT51_BIT,
AC_PTE_BIT36_BIT,
- AC_PDE_PRESENT_BIT,
AC_PDE_WRITABLE_BIT,
AC_PDE_USER_BIT,
AC_PDE_ACCESSED_BIT,
AC_PDE_DIRTY_BIT,
AC_PDE_PSE_BIT,
AC_PDE_NX_BIT,
+ AC_PDE_PRESENT_BIT,
AC_PDE_BIT51_BIT,
AC_PDE_BIT36_BIT,
AC_PDE_BIT13_BIT,
--
2.34.0.rc2.393.gf8c9666880-goog
