Xen devel - May 2012 - [PATCH] x86/hvm: put value of emulated register reads into trace records

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

The tracepoint for emulated MMIO and I/O port reads was always before
the emulated read or write was done.  This means that for reads the
register value in the trace record was always 0.

So for reads, move the tracepoint until the register value is
available.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Cc: George Dunlap <george.dunlap@citrix.com>
---
A candidate for 4.0 and 4.1?
---
 xen/arch/x86/hvm/emulate.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 82efd1a..3a7fe95 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -191,7 +191,8 @@ static int hvmemul_do_io(
     p->df = df;
     p->data = value;
 
-    hvmtrace_io_assist(is_mmio, p);
+    if ( dir == IOREQ_WRITE )
+        hvmtrace_io_assist(is_mmio, p);
 
     if ( is_mmio )
     {
@@ -232,6 +233,9 @@ static int hvmemul_do_io(
     }
 
  finish_access:
+    if ( dir == IOREQ_READ )
+        hvmtrace_io_assist(is_mmio, p);
+
     if ( p_data != NULL )
         memcpy(p_data, &vio->io_data, size);
 
-- 
1.7.2.5