[PATCH] xen mtrr: Implement xen_get_free_region()

[Jeremy Fitzhardinge]

From: Mark McLoughlin <markmc@xxxxxxxxxx>

When an already set MTRR is being changed, we need to
first unset, since Xen also maintains a usage count.

Signed-off-by: Mark McLoughlin <markmc@xxxxxxxxxx>
---
 arch/x86/kernel/cpu/mtrr/xen.c |   27 ++++++++++++++++++++++++++-
 1 files changed, 26 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/xen.c b/arch/x86/kernel/cpu/mtrr/xen.c
index f226044..d715843 100644
--- a/arch/x86/kernel/cpu/mtrr/xen.c
+++ b/arch/x86/kernel/cpu/mtrr/xen.c
@@ -9,13 +9,38 @@
 
 static int __init xen_num_var_ranges(void);
 
+static int xen_get_free_region(unsigned long base, unsigned long size, int replace_reg)
+{
+	struct xen_platform_op op;
+	int error;
+
+	if (replace_reg < 0)
+		return generic_get_free_region(base, size, -1);
+
+	/* If we're replacing the contents of a register,
+	 * we need to first unset it since Xen also keeps
+	 * a usage count.
+	 */
+	op.cmd = XENPF_del_memtype;
+	op.u.del_memtype.handle = 0;
+	op.u.del_memtype.reg    = replace_reg;
+
+	error = HYPERVISOR_dom0_op(&op);
+	if (error) {
+		BUG_ON(error > 0);
+		return error;
+	}
+
+	return replace_reg;
+}
+
 /* DOM0 TODO: Need to fill in the remaining mtrr methods to have full
  * working userland mtrr support. */
 static struct mtrr_ops xen_mtrr_ops = {
 	.vendor            = X86_VENDOR_UNKNOWN,
 //	.set               = xen_set_mtrr,
 //	.get               = xen_get_mtrr,
-	.get_free_region   = generic_get_free_region,
+	.get_free_region   = xen_get_free_region,
 	.validate_add_page = generic_validate_add_page,
 	.have_wrcomb       = positive_have_wrcomb,
 	.use_intel_if	   = 0,
-- 
1.6.0.6

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