This new KVM exit allows userspace to handle memory-related errors. It
indicates an error happens in KVM at guest memory range [gpa, gpa+size).
The flags includes additional information for userspace to handle the
error. Currently bit 0 is defined as 'private memory' where '1'
indicates error happens due to private memory access and '0' indicates
error happens due to shared memory access.

When private memory is enabled, this new exit will be used for KVM to
exit to userspace for shared <-> private memory conversion in memory
encryption usage. In such usage, typically there are two kind of memory
conversions:
  - explicit conversion: happens when guest explicitly calls into KVM
    to map a range (as private or shared), KVM then exits to userspace
    to perform the map/unmap operations.
  - implicit conversion: happens in KVM page fault handler where KVM
    exits to userspace for an implicit conversion when the page is in a
    different state than requested (private or shared).

Suggested-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Yu Zhang <redacted>
Signed-off-by: Yu Zhang <redacted>
Signed-off-by: Chao Peng <redacted>
---
 Documentation/virt/kvm/api.rst | 23 +++++++++++++++++++++++
 include/uapi/linux/kvm.h       |  9 +++++++++
 2 files changed, 32 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst 

b/Documentation/virt/kvm/api.rst
index f3fa75649a78..975688912b8c 100644

--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst

@@ -6537,6 +6537,29 @@ array field represents return values. The 

userspace should update the return
 values of SBI call before resuming the VCPU. For more details on 
RISC-V SBI
 spec refer, https://github.com/riscv/riscv-sbi-doc.

+::
+
+		/* KVM_EXIT_MEMORY_FAULT */
+		struct {
+  #define KVM_MEMORY_EXIT_FLAG_PRIVATE	(1 << 0)
+			__u32 flags;
+			__u32 padding;
+			__u64 gpa;
+			__u64 size;
+		} memory;
+