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>
Reviewed-by: Fuad Tabba <redacted>
Tested-by: Fuad Tabba <redacted>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 Documentation/virt/kvm/api.rst | 22 ++++++++++++++++++++++
 include/uapi/linux/kvm.h       |  8 ++++++++
 2 files changed, 30 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index c0ddd3035462..34d4ce66e0c8 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst

@@ -6700,6 +6700,28 @@ 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	(1ULL << 3)
+			__u64 flags;
+			__u64 gpa;
+			__u64 size;
+		} memory;
+
+If exit reason is KVM_EXIT_MEMORY_FAULT then it indicates that the VCPU has
+encountered a memory error which is not handled by KVM kernel module and
+userspace may choose to handle it. The 'flags' field indicates the memory
+properties of the exit.
+
+ - KVM_MEMORY_EXIT_FLAG_PRIVATE - indicates the memory error is caused by
+   private memory access when the bit is set. Otherwise the memory error is
+   caused by shared memory access when the bit is clear.
+
+'gpa' and 'size' indicate the memory range the error occurs at. The userspace
+may handle the error and return to KVM to retry the previous memory access.
+
 ::

     /* KVM_EXIT_NOTIFY */

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 4d4b3de8ac55..6c6ed214b6ac 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h

@@ -274,6 +274,7 @@ struct kvm_xen_exit {
 #define KVM_EXIT_RISCV_SBI        35
 #define KVM_EXIT_RISCV_CSR        36
 #define KVM_EXIT_NOTIFY           37
+#define KVM_EXIT_MEMORY_FAULT     38

 /* For KVM_EXIT_INTERNAL_ERROR */
 /* Emulate instruction failed. */

@@ -520,6 +521,13 @@ struct kvm_run {
 #define KVM_NOTIFY_CONTEXT_INVALID	(1 << 0)
 			__u32 flags;
 		} notify;
+		/* KVM_EXIT_MEMORY_FAULT */
+		struct {
+#define KVM_MEMORY_EXIT_FLAG_PRIVATE	(1ULL << 3)
+			__u64 flags;
+			__u64 gpa;
+			__u64 size;
+		} memory;
 		/* Fix the size of the union. */
 		char padding[256];
 	};
--

2.41.0.255.g8b1d071c50-goog