[RFC PATCH 07/13] kvm: Add docs for KVM_CAP_EXECONLY_MEM

[Rick Edgecombe]

Add documentation for the KVM_CAP_EXECONLY_MEM capability and
KVM_MEM_EXECONLY memslot.

Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
---
 Documentation/virt/kvm/api.txt | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index 2d067767b617..a8001f996a8a 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -1096,6 +1096,7 @@ struct kvm_userspace_memory_region {
 /* for kvm_memory_region::flags */
 #define KVM_MEM_LOG_DIRTY_PAGES	(1UL << 0)
 #define KVM_MEM_READONLY	(1UL << 1)
+#define KVM_MEM_EXECONLY	(1UL << 2)
 
 This ioctl allows the user to create, modify or delete a guest physical
 memory slot.  Bits 0-15 of "slot" specify the slot id and this value
@@ -1123,12 +1124,15 @@ It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
 be identical.  This allows large pages in the guest to be backed by large
 pages in the host.
 
-The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and
-KVM_MEM_READONLY.  The former can be set to instruct KVM to keep track of
-writes to memory within the slot.  See KVM_GET_DIRTY_LOG ioctl to know how to
-use it.  The latter can be set, if KVM_CAP_READONLY_MEM capability allows it,
-to make a new slot read-only.  In this case, writes to this memory will be
-posted to userspace as KVM_EXIT_MMIO exits.
+The flags field supports three flags: KVM_MEM_LOG_DIRTY_PAGES, KVM_MEM_READONLY
+and KVM_MEM_EXECONLY.  KVM_MEM_LOG_DIRTY_PAGES can be set to instruct KVM to
+keep track of writes to memory within the slot.  See KVM_GET_DIRTY_LOG ioctl to
+know how to use it.  KVM_MEM_READONLY can be set, if KVM_CAP_READONLY_MEM
+capability allows it, to make a new slot read-only.  In this case, writes to
+this memory will be posted to userspace as KVM_EXIT_MMIO exits. KVM_MEM_EXECONLY
+can be set, if KVM_CAP_EXECONLY_MEM capability allows it, to make a new slot
+exec-only. Guest read accesses to KVM_CAP_EXECONLY_MEM will trigger an
+appropriate fault injected into the guest, in support of X86_FEATURE_KVM_XO.
 
 When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of
 the memory region are automatically reflected into the guest.  For example, an
-- 
2.17.1