[PATCH 09/45] KVM: Define and communicate KVM_EXIT_MEMORY_FAULT RWX flags to userspace

[Paolo Bonzini]

From: Anish Moorthy <amoorthy@xxxxxxxxxx>

kvm_prepare_memory_fault_exit() already takes parameters describing the
RWX-ness of the relevant access but doesn't actually do anything with
them. Define and use the flags necessary to pass this information on to
userspace.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Link: https://lore.kernel.org/kvm/ZR4N8cwzTMDanPUY@xxxxxxxxxx/
Signed-off-by: Anish Moorthy <amoorthy@xxxxxxxxxx>
Signed-off-by: Nicolas Saenz Julienne <nsaenz@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Link: https://patch.msgid.link/20260918135030.171564-4-pbonzini@xxxxxxxxxx
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 Documentation/virt/kvm/api.rst | 5 +++++
 include/linux/kvm_host.h       | 9 ++++++++-
 include/uapi/linux/kvm.h       | 3 +++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index e95c9cda085d..7123d021bdbb 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -7481,6 +7481,9 @@ spec refer, https://github.com/riscv/riscv-sbi-doc.
 
 		/* KVM_EXIT_MEMORY_FAULT */
 		struct {
+  #define KVM_MEMORY_EXIT_FLAG_READ     (1ULL << 0)
+  #define KVM_MEMORY_EXIT_FLAG_WRITE    (1ULL << 1)
+  #define KVM_MEMORY_EXIT_FLAG_EXEC     (1ULL << 2)
   #define KVM_MEMORY_EXIT_FLAG_PRIVATE	(1ULL << 3)
 			__u64 flags;
 			__u64 gpa;
@@ -7492,6 +7495,8 @@ 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
 describes properties of the faulting access that are likely pertinent:
 
+ - KVM_MEMORY_EXIT_FLAG_READ/WRITE/EXEC - When set, indicates that the memory
+   fault occurred on a read/write/exec access respectively.
  - KVM_MEMORY_EXIT_FLAG_PRIVATE - When set, indicates the memory fault occurred
    on a private memory access.  When clear, indicates the fault occurred on a
    shared access.
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e7fc94e2910a..5e386c3d2495 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2556,8 +2556,15 @@ static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,
 	vcpu->run->memory_fault.gpa = gpa;
 	vcpu->run->memory_fault.size = size;
 
-	/* RWX flags are not (yet) defined or communicated to userspace. */
 	vcpu->run->memory_fault.flags = 0;
+
+	if (is_write)
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_WRITE;
+	else if (is_exec)
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_EXEC;
+	else
+		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_READ;
+
 	if (is_private)
 		vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_PRIVATE;
 }
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8dff2fc1972e..229b3bdb7aed 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -457,6 +457,9 @@ struct kvm_run {
 		} notify;
 		/* KVM_EXIT_MEMORY_FAULT */
 		struct {
+#define KVM_MEMORY_EXIT_FLAG_READ       (1ULL << 0)
+#define KVM_MEMORY_EXIT_FLAG_WRITE      (1ULL << 1)
+#define KVM_MEMORY_EXIT_FLAG_EXEC       (1ULL << 2)
 #define KVM_MEMORY_EXIT_FLAG_PRIVATE	(1ULL << 3)
 			__u64 flags;
 			__u64 gpa;
-- 
2.52.0