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 <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>

2 files changed, 36 insertions, 0 deletions

diff --git a/arch/i386/kernel/paravirt.c b/arch/i386/kernel/paravirt.c
index faab09abca5e..60e08b9b50a4 100644
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -228,6 +228,41 @@ static int __init print_banner(void)
 }
 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;
+
+        ret = request_resource(&ioport_resource, &reserve_ioports);
+        if (ret == 0) {
+                ret = request_resource(&iomem_resource, &reserve_iomem);
+                if (ret)
+                        release_resource(&reserve_ioports);
+        }
+
+        return ret;
+}
+
 struct paravirt_ops paravirt_ops = {
         .name = "bare hardware",
         .paravirt_enabled = 0,
diff --git a/include/asm-i386/paravirt.h b/include/asm-i386/paravirt.h
index 786856950b1a..690ada22437a 100644
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -262,6 +262,7 @@ unsigned paravirt_patch_default(u8 type, u16 clobbers, void *site, unsigned len)
 unsigned paravirt_patch_insns(void *site, unsigned len,
                               const char *start, const char *end);
 
+int paravirt_disable_iospace(void);
 
 /*
  * This generates an indirect call based on the operation type number.