[PATCH v2 1/3] KVM: Documentation: Clarify docs for KVM_CAP_MEMORY_FAULT_INFO

[Anish Moorthy <amoorthy@google.com>]

The initial paragraph of the documentation here makes it sound like a
KVM_EXIT_MEMORY_FAULT will always accompany an EFAULT from KVM_RUN, but
that's not a guarantee.

Also, define zero to be a special value for the "size" field. This
allows memory faults exits to be set up in spots where KVM_RUN must
EFAULT, but is not able to supply an accurate size.

Signed-off-by: Anish Moorthy <amoorthy@google.com>
---
 Documentation/virt/kvm/api.rst | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 8e5dad80b337..c5ce7944005c 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -7073,7 +7073,8 @@ spec refer, https://github.com/riscv/riscv-sbi-doc.
 
 KVM_EXIT_MEMORY_FAULT indicates the vCPU has encountered a memory fault that
 could not be resolved by KVM.  The 'gpa' and 'size' (in bytes) describe the
-guest physical address range [gpa, gpa + size) of the fault.  The 'flags' field
+guest physical address range [gpa, gpa + size) of the fault: when zero, it
+indicates that the size of the fault could not be determined. The 'flags' field
 describes properties of the faulting access that are likely pertinent:
 
  - KVM_MEMORY_EXIT_FLAG_PRIVATE - When set, indicates the memory fault occurred
@@ -8131,7 +8132,7 @@ unavailable to host or other VMs.
 :Architectures: x86
 :Returns: Informational only, -EINVAL on direct KVM_ENABLE_CAP.
 
-The presence of this capability indicates that KVM_RUN will fill
+The presence of this capability indicates that KVM_RUN *may* fill
 kvm_run.memory_fault if KVM cannot resolve a guest page fault VM-Exit, e.g. if
 there is a valid memslot but no backing VMA for the corresponding host virtual
 address.
-- 
2.46.0.76.ge559c4bf1a-goog