Re: [PATCH] paravirt: helper to disable all IO space

In a virtual environment, device drivers such as legacy IDE will waste
quite a lot of time probing for their devices which will never appear.
This helper function allows a paravirt implementation to lay claim to
the whole iomem and ioport space, thereby disabling all device drivers
trying to claim IO resources.

Signed-off-by: Jeremy Fitzhardinge <redacted>
Cc: Rusty Russell <redacted>

diff -r 83c67f9402b5 arch/i386/kernel/paravirt.c

--- a/arch/i386/kernel/paravirt.c	Tue Jun 05 17:41:04 2007 -0700
+++ b/arch/i386/kernel/paravirt.c	Tue Jun 05 18:17:29 2007 -0700

@@ -227,6 +227,39 @@ static int __init print_banner(void)
 	return 0;
 }
 core_initcall(print_banner);
+
+static struct resource reserve_ioports = {
+	.start = 0,
+	.end = IO_SPACE_LIMIT,
+	.name = "paravirt-ioport",
+	.flags = IORESOURCE_IO | IORESOURCE_BUSY,
+};
+
+static struct resource reserve_iomem = {
+	.start = 0,
+	.end = -1,
+	.name = "paravirt-iomem",
+	.flags = IORESOURCE_MEM | IORESOURCE_BUSY,
+};
+
+/*
+ * Reserve the whole legacy IO space to prevent any legacy drivers
+ * from wasting time probing for their hardware.  This is a fairly
+ * brute-force approach to disabling all non-virtual drivers.
+ * 
+ * Note that this must be called very early to have any effect.
+ */
+int paravirt_disable_iospace(void)
+{
+	int ret = 0;
+
+	ret = request_resource(&ioport_resource, &reserve_ioports);
+	if (ret == 0)
+		ret = request_resource(&iomem_resource, &reserve_iomem);
+
+	return ret;
+}
+
 
 struct paravirt_ops paravirt_ops = {
 	.name = "bare hardware",

diff -r 83c67f9402b5 arch/i386/xen/setup.c

--- a/arch/i386/xen/setup.c	Tue Jun 05 17:41:04 2007 -0700
+++ b/arch/i386/xen/setup.c	Tue Jun 05 18:17:29 2007 -0700