[Xen-devel] [patch 15/44] paravirt: helper to disable all IO space

[Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>]

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@xxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>

---
 arch/i386/kernel/paravirt.c |   35 +++++++++++++++++++++++++++++++++++
 include/asm-i386/paravirt.h |    1 +
 2 files changed, 36 insertions(+)

===================================================================
--- a/arch/i386/kernel/paravirt.c
+++ b/arch/i386/kernel/paravirt.c
@@ -227,6 +227,41 @@ 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;
+
+       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",
===================================================================
--- a/include/asm-i386/paravirt.h
+++ b/include/asm-i386/paravirt.h
@@ -262,6 +262,7 @@ unsigned paravirt_patch_insns(void *site
 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.

-- 


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