On Mon, Mar 28, 2022 at 10:33:37PM +0000, Sean Christopherson wrote:

On Thu, Mar 10, 2022, Chao Peng wrote:

quoted

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.

After private memory is enabled, this new exit will be used for KVM to
exit to userspace for shared memory <-> 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
    do the map/unmap operations.
  - implicit conversion: happens in KVM page fault handler.
    * if the fault is due to a private memory access then causes a
      userspace exit for a shared->private conversion request when the
      page has not been allocated in the private memory backend.
    * If the fault is due to a shared memory access then causes a
      userspace exit for a private->shared conversion request when the
      page has already been allocated in the private memory backend.

Signed-off-by: Yu Zhang <redacted>
Signed-off-by: Chao Peng <redacted>
---
 Documentation/virt/kvm/api.rst | 22 ++++++++++++++++++++++
 include/uapi/linux/kvm.h       |  9 +++++++++
 2 files changed, 31 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index f76ac598606c..bad550c2212b 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst

@@ -6216,6 +6216,28 @@ 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_ERROR */
+		struct {
+  #define KVM_MEMORY_EXIT_FLAG_PRIVATE	(1 << 0)
+			__u32 flags;
+			__u32 padding;
+			__u64 gpa;
+			__u64 size;
+		} memory;
+If exit reason is KVM_EXIT_MEMORY_ERROR then it indicates that the VCPU has

Doh, I'm pretty sure I suggested KVM_EXIT_MEMORY_ERROR.  Any objection to using
KVM_EXIT_MEMORY_FAULT instead of KVM_EXIT_MEMORY_ERROR?  "ERROR" makes me think
of ECC errors, i.e. uncorrected #MC in x86 land, not more generic "faults".  That
would align nicely with -EFAULT.

Sure.

quoted

+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.