diff mbox series

[v6,04/14] KVM: Define and communicate KVM_EXIT_MEMORY_FAULT RWX flags to userspace

Message ID 20231109210325.3806151-5-amoorthy@google.com (mailing list archive)
State New, archived
Headers show
Series Improve KVM + userfaultfd performance via KVM_MEMORY_FAULT_EXITs on stage-2 faults | expand

Commit Message

Anish Moorthy Nov. 9, 2023, 9:03 p.m. UTC 
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Anish Moorthy <amoorthy@google.com>
---
 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(-)

Comments

Sean Christopherson Feb. 7, 2024, 3:30 p.m. UTC | #1 
On Thu, Nov 09, 2023, Anish Moorthy wrote:

Needs a changelog.

> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Anish Moorthy <amoorthy@google.com>
> ---
Anish Moorthy Feb. 7, 2024, 6:57 p.m. UTC | #2 
On Wed, Feb 7, 2024 at 7:31 AM Sean Christopherson <seanjc@google.com> wrote:
>
> Needs a changelog.

Urgh, that's embarrassing: I'll use the following absent any objections

> kvm_prepare_memory_fault_exit() already takes parameters describing the R/W/X
> nature of the relevant access but doesn't actually do anything with them. Define
> and utilize the flags necessary to pass this information on to userspace.
diff mbox series

Patch

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index c13ede498369..a07964f601de 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6979,6 +6979,9 @@  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;
@@ -6990,6 +6993,8 @@  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 4d5d139b0bde..5201400358da 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2372,8 +2372,15 @@  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 b4ba4b53b834..bda5622a9c68 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -535,6 +535,9 @@  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;