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authorPeter Feiner <pfeiner@google.com>2017-06-30 17:26:31 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2017-07-03 11:19:54 +0200
commitac8d57e5734389da18633d4e8cc030fe10843da7 (patch)
treecc5aec1dd7bd4f36366aa6a064f9970c1e77c20d /Documentation/virtual
parentdcdca5fed5f6ef2521f927ba3b5cd6b328054be1 (diff)
kvm: x86: mmu: allow A/D bits to be disabled in an mmu
Adds the plumbing to disable A/D bits in the MMU based on a new role bit, ad_disabled. When A/D is disabled, the MMU operates as though A/D aren't available (i.e., using access tracking faults instead). To avoid SP -> kvm_mmu_page.role.ad_disabled lookups all over the place, A/D disablement is now stored in the SPTE. This state is stored in the SPTE by tweaking the use of SPTE_SPECIAL_MASK for access tracking. Rather than just setting SPTE_SPECIAL_MASK when an access-tracking SPTE is non-present, we now always set SPTE_SPECIAL_MASK for access-tracking SPTEs. Signed-off-by: Peter Feiner <pfeiner@google.com> [Use role.ad_disabled even for direct (non-shadow) EPT page tables. Add documentation and a few MMU_WARN_ONs. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virtual')
-rw-r--r--Documentation/virtual/kvm/mmu.txt4
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/mmu.txt b/Documentation/virtual/kvm/mmu.txt
index 481b6a9c25d5..f50d45b1e967 100644
--- a/Documentation/virtual/kvm/mmu.txt
+++ b/Documentation/virtual/kvm/mmu.txt
@@ -179,6 +179,10 @@ Shadow pages contain the following information:
shadow page; it is also used to go back from a struct kvm_mmu_page
to a memslot, through the kvm_memslots_for_spte_role macro and
__gfn_to_memslot.
+ role.ad_disabled:
+ Is 1 if the MMU instance cannot use A/D bits. EPT did not have A/D
+ bits before Haswell; shadow EPT page tables also cannot use A/D bits
+ if the L1 hypervisor does not enable them.
gfn:
Either the guest page table containing the translations shadowed by this
page, or the base page frame for linear translations. See role.direct.