[Xen-changelog] [xen-unstable] [XEN] Allow direct reads of port 0x61 by any guest.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 8c0cf4d3c4120b0b91a9a76a67f4005822cb7a7f
# Parent  3bff5c5b9206eec951e649aff006379009dc5a2a
[XEN] Allow direct reads of port 0x61 by any guest.
Often used by BIOS code which may be executed e.g., when starting
an X server.
From: Jan Beulich <jbeulich@xxxxxxxxxx>
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
 xen/arch/x86/traps.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletion(-)

diff -r 3bff5c5b9206 -r 8c0cf4d3c412 xen/arch/x86/traps.c
--- a/xen/arch/x86/traps.c      Wed Sep 13 14:34:34 2006 +0100
+++ b/xen/arch/x86/traps.c      Wed Sep 13 14:46:54 2006 +0100
@@ -1003,7 +1003,21 @@ static inline int admin_io_okay(
 }
 
 /* Check admin limits. Silently fail the access if it is disallowed. */
-#define inb_user(_p, _d, _r) (admin_io_okay(_p, 1, _d, _r) ? inb(_p) : ~0)
+static inline unsigned char inb_user(
+    unsigned int port, struct vcpu *v, struct cpu_user_regs *regs)
+{
+    /*
+     * Allow read access to port 0x61. Bit 4 oscillates with period 30us, and
+     * so it is often used for timing loops in BIOS code. This hack can go
+     * away when we have separate read/write permission rangesets.
+     * Note that we could emulate bit 4 instead of directly reading port 0x61,
+     * but there's not really a good reason to do so.
+     */
+    if ( admin_io_okay(port, 1, v, regs) || (port == 0x61) )
+        return inb(port);
+    return ~0;
+}
+//#define inb_user(_p, _d, _r) (admin_io_okay(_p, 1, _d, _r) ? inb(_p) : ~0)
 #define inw_user(_p, _d, _r) (admin_io_okay(_p, 2, _d, _r) ? inw(_p) : ~0)
 #define inl_user(_p, _d, _r) (admin_io_okay(_p, 4, _d, _r) ? inl(_p) : ~0)
 #define outb_user(_v, _p, _d, _r) \

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-changelog