[PATCH v9 11/11] x86/vm_event: add response flag to reset vmtrace buffer

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

From: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>

Allow resetting the vmtrace buffer in response to a vm_event. This can be used
to optimize a use-case where detecting a looped vmtrace buffer is important.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/vm_event.c        | 7 +++++++
 xen/common/vm_event.c          | 3 +++
 xen/include/asm-arm/vm_event.h | 6 ++++++
 xen/include/asm-x86/vm_event.h | 2 ++
 xen/include/public/vm_event.h  | 4 ++++
 5 files changed, 22 insertions(+)

diff --git a/xen/arch/x86/vm_event.c b/xen/arch/x86/vm_event.c
index 36272e9316..8f73a73e2e 100644
--- a/xen/arch/x86/vm_event.c
+++ b/xen/arch/x86/vm_event.c
@@ -300,6 +300,13 @@ void vm_event_emulate_check(struct vcpu *v, 
vm_event_response_t *rsp)
     };
 }
 
+void vm_event_reset_vmtrace(struct vcpu *v)
+{
+#ifdef CONFIG_HVM
+    hvm_vmtrace_reset(v);
+#endif
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/common/vm_event.c b/xen/common/vm_event.c
index 127f2d58f1..44d542f23e 100644
--- a/xen/common/vm_event.c
+++ b/xen/common/vm_event.c
@@ -424,6 +424,9 @@ static int vm_event_resume(struct domain *d, struct 
vm_event_domain *ved)
             if ( rsp.flags & VM_EVENT_FLAG_GET_NEXT_INTERRUPT )
                 vm_event_monitor_next_interrupt(v);
 
+            if ( rsp.flags & VM_EVENT_FLAG_RESET_VMTRACE )
+                vm_event_reset_vmtrace(v);
+
             if ( rsp.flags & VM_EVENT_FLAG_VCPU_PAUSED )
                 vm_event_vcpu_unpause(v);
         }
diff --git a/xen/include/asm-arm/vm_event.h b/xen/include/asm-arm/vm_event.h
index 14d1d341cc..abe7db1970 100644
--- a/xen/include/asm-arm/vm_event.h
+++ b/xen/include/asm-arm/vm_event.h
@@ -58,4 +58,10 @@ void vm_event_sync_event(struct vcpu *v, bool value)
     /* Not supported on ARM. */
 }
 
+static inline
+void vm_event_reset_vmtrace(struct vcpu *v)
+{
+    /* Not supported on ARM. */
+}
+
 #endif /* __ASM_ARM_VM_EVENT_H__ */
diff --git a/xen/include/asm-x86/vm_event.h b/xen/include/asm-x86/vm_event.h
index 785e741fba..0756124075 100644
--- a/xen/include/asm-x86/vm_event.h
+++ b/xen/include/asm-x86/vm_event.h
@@ -54,4 +54,6 @@ void vm_event_emulate_check(struct vcpu *v, 
vm_event_response_t *rsp);
 
 void vm_event_sync_event(struct vcpu *v, bool value);
 
+void vm_event_reset_vmtrace(struct vcpu *v);
+
 #endif /* __ASM_X86_VM_EVENT_H__ */
diff --git a/xen/include/public/vm_event.h b/xen/include/public/vm_event.h
index 147dc3ea73..36135ba4f1 100644
--- a/xen/include/public/vm_event.h
+++ b/xen/include/public/vm_event.h
@@ -123,6 +123,10 @@
  * Set if the event comes from a nested VM and thus npt_base is valid.
  */
 #define VM_EVENT_FLAG_NESTED_P2M         (1 << 12)
+/*
+ * Reset the vmtrace buffer (if vmtrace is enabled)
+ */
+#define VM_EVENT_FLAG_RESET_VMTRACE      (1 << 13)
 
 /*
  * Reasons for the vm event request
-- 
2.11.0