[PATCH 3/3] libxc: add xc_tbuf_trace() to insert trace records

[David Vrabel <david.vrabel@citrix.com>]

From: David Vrabel <david.vrabel@citrix.com>

Add xc_tbuf_trace() to allow trace records to be added to the trace
buffer.  The subclass and event number and up to 7 uin32_t arguments
may be specified.

The hypercall sub-op used is HVMOP_xentrace which (despite the name)
may be used by PV guests.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
---
 tools/libxc/xc_tbuf.c  |   39 +++++++++++++++++++++++++++++++++++++++
 tools/libxc/xenctrl.h  |   11 +++++++++++
 xen/arch/x86/hvm/hvm.c |    2 +-
 3 files changed, 51 insertions(+), 1 deletions(-)

diff --git a/tools/libxc/xc_tbuf.c b/tools/libxc/xc_tbuf.c
index 4fb7bb1..0644952 100644
--- a/tools/libxc/xc_tbuf.c
+++ b/tools/libxc/xc_tbuf.c
@@ -156,3 +156,42 @@ int xc_tbuf_set_evt_mask(xc_interface *xch, uint32_t mask)
     return do_sysctl(xch, &sysctl);
 }
 
+int xc_tbuf_trace(xc_interface *xch, uint16_t event, unsigned nr_args, ...)
+{
+    DECLARE_HYPERCALL;
+    DECLARE_HYPERCALL_BUFFER(xen_hvm_xentrace_t, trace);
+    unsigned i;
+    va_list args;
+    int ret = -1;
+
+    if ( nr_args > 7 ) {
+        errno = -EINVAL;
+        goto out;
+    }
+
+    trace = xc_hypercall_buffer_alloc(xch, trace, sizeof(*trace));
+    if ( trace == NULL )
+    {
+        PERROR("Count not alloc bounce buffer for trace hypercall");
+        goto out;
+    }
+
+    trace->event = event;
+    trace->extra_bytes = nr_args * sizeof(uint32_t);
+
+    va_start(args, nr_args);
+    for (i = 0; i < nr_args; i++)
+        ((uint32_t *)trace->extra)[i] = va_arg(args, uint32_t);
+    va_end(args);
+
+    hypercall.op = __HYPERVISOR_hvm_op;
+    hypercall.arg[0] = HVMOP_xentrace;
+    hypercall.arg[1] = HYPERCALL_BUFFER_AS_ARG(trace);
+
+    ret = do_xen_hypercall(xch, &hypercall);
+
+out:
+    xc_hypercall_buffer_free(xch, trace);
+
+    return ret;
+}
diff --git a/tools/libxc/xenctrl.h b/tools/libxc/xenctrl.h
index 388a9c3..927b198 100644
--- a/tools/libxc/xenctrl.h
+++ b/tools/libxc/xenctrl.h
@@ -1387,6 +1387,17 @@ int xc_tbuf_set_cpu_mask(xc_interface *xch, uint32_t mask);
 
 int xc_tbuf_set_evt_mask(xc_interface *xch, uint32_t mask);
 
+/**
+ * Insert a trace record into the trace buffer.
+ *
+ * The trace records use the TRC_GUEST class and 'event' sets the
+ * sub-class and the event number.  There are no predefined values for
+ * these.
+ *
+ * Up to 7 uint32_t arguments may be included in the trace record.
+ */
+int xc_tbuf_trace(xc_interface *xch, uint16_t event, unsigned nr_args, ...);
+
 int xc_domctl(xc_interface *xch, struct xen_domctl *domctl);
 int xc_sysctl(xc_interface *xch, struct xen_sysctl *sysctl);
 
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index b0d8094..b24a37d 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4388,7 +4388,7 @@ long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
             return -EFAULT;
 
         if ( tr.extra_bytes > sizeof(tr.extra)
-             || (tr.event & ~((1u<<TRC_CLS_SHIFT)-1)) )
+             || (tr.event & ~((1u<<TRC_SUBCLS_SHIFT)-1)) )
             return -EINVAL;
 
         trace_var(TRC_GUEST_EVENT(tr.event), 1 /*cycles*/,
-- 
1.7.2.5