To begin with: I am using xen-unstable-3.2.0 changeset 16747.
I am trying to add a small and quick Hypercall for some performance
related testing on xen (using xenoprofile isn’t feasible since we already
have our tools working on native linux and would only like to add some features
to make it work under Xen). The basic idea is that our application will issue a
hypercall that we install into xen and then the hypercall does what we tell it
to do and returns with the results. Here’s a _trimmed/cleaned out_
version of the dummy hypercall, just to show you which files have been touched :
+++ xen-unstable.hg/xen/arch/x86/x86_32/entry.S 2008-04-25
21:44:11.000000000 -0500
@@ -682,6 +682,7 @@
.long do_kexec_op
+ .long
do_perfcall_op /* 38 */
@@ -725,6 +726,7 @@
.byte 2 /*
do_kexec_op */
+ .byte 2 /*
do_perfcall_op */
--- xen-unstable.hg-orig/xen/arch/x86/x86_64/entry.S
2008-04-22 14:14:57.000000000 -0500
+++ xen-unstable.hg/xen/arch/x86/x86_64/entry.S 2008-04-25
21:43:37.000000000 -0500
@@ -672,6 +672,7 @@
.quad do_kexec_op
+ .quad
do_perfcall_op /*38 - added for perflab hack
--hrm */
.rept
NR_hypercalls-((.-hypercall_table)/8)
@@ -716,6 +717,7 @@
.byte 1 /*
do_xsm_op */
+ .byte 2 /*
do_perfcall_op */
--- xen-unstable.hg-orig/xen/common/Makefile 2008-04-22
14:14:57.000000000 -500
+++ xen-unstable.hg/xen/common/Makefile 2008-04-24 20:33:09.000000000
-0500
@@ -26,6 +26,7 @@
obj-y += rcupdate.o
+obj-y += perfcall.o
--- xen-unstable.hg-orig/xen/common/perfcall.c
1969-12-31 18:00:00.000000000 -0600
+++ xen-unstable.hg/xen/common/perfcall.c 2008-04-30
21:55:56.000000000 -0500
@@ -0,0 +1,52 @@
...
<this is where the hypercall ‘do_perfcall_op’ is
implemented; currently it just returns the xen-version >
...
--- xen-unstable.hg-orig/xen/include/public/xen.h 2008-04-22
14:14:57.000000000 -0500
+++ xen-unstable.hg/xen/include/public/xen.h 2008-04-29
18:33:15.000000000 -0500
@@ -80,6 +80,7 @@
#define
__HYPERVISOR_kexec_op
37
+#define
__HYPERVISOR_perfcall_op
38
--- xen-unstable.hg-orig/xen/include/xen/hypercall.h
2008-04-22 14:14:58.000000000 -0500
+++ xen-unstable.hg/xen/include/xen/hypercall.h 2008-04-25
18:27:35.000000000 -0500
@@ -116,6 +116,11 @@
+extern long
+do_perfcall_op(
+ int cmd,
+ XEN_GUEST_HANDLE(void)
arg);
+
--
I 'make; make install' the modified xen. I see the 'do_perfcall_op'
symbol in the latest /boot/xen-syms file.
Now, I trying to compile a kernel driver on Dom0 that will call this
hypercall via (HYPERVISOR_perfcall_op()). However, the compiler isn't able to
translate HYPERVISOR_perfcall_op and errors out. If I use
HYPERVISOR_xen_version() in its place, it works OK.
I am guessing there is some header file I am not modifying that'll tell
Dom0 about this new hypercall (although I do see an entry for
__HYPERVISOR_perfcall_op in /usr/include/xen/xen.h)? Is it because the
correct hypercall doesn't exist in the hypercall page at the right place? What
am I missing?
Thanks for your inputs.
Hemant
