From: Keir Fraser <keir.fraser@citrix.com>
Date: Fri, 20 Mar 2009 08:42:14 +0000 (+0000)
Subject: hvm: Allow HVM guests direct access to 0xed debug/delay port
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~13992^2~23
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks://%22Dat/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22Dat?a=commitdiff_plain;h=f7ffd86d525591a1ade3554b5275a7fe604c0553;p=xen.git

hvm: Allow HVM guests direct access to 0xed debug/delay port

Port 0x80 is already passed-through.  Writes to port 0x80 are
traditionally used as IO delay.  Recent Linux kernel versions can be
configured to use port 0xed instead (CONFIG_IO_DELAY_0XED=3Dy).
Ubuntu 8.04 and later kernels are configured to use port 0xed.

In Linux IO delay is implemented by (in|out)[bwl]_p.  From a first
glance at Linux it looks like the only relevant usage of delayed IO is
in drivers/video/console/vgacon.c.  Affected is VGA console
initialization and font setup.  Output / scrolling is not affected.

Signed-off-by: Thomas Friebel <thomas.friebel@amd.com>
---

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index c8c53c6244..9a6d6cd5a1 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -74,11 +74,12 @@ void hvm_enable(struct hvm_function_table *fns)
     printk("HVM: %s enabled\n", fns->name);
 
     /*
-     * Allow direct access to the PC debug port (it is often used for I/O
-     * delays, but the vmexits simply slow things down).
+     * Allow direct access to the PC debug ports 0x80 and 0xed (they are
+     * often used for I/O delays, but the vmexits simply slow things down).
      */
     memset(hvm_io_bitmap, ~0, sizeof(hvm_io_bitmap));
     __clear_bit(0x80, hvm_io_bitmap);
+    __clear_bit(0xed, hvm_io_bitmap);
 
     hvm_funcs   = *fns;
     hvm_enabled = 1;