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[Xen-devel] [PATCH] xen mtrr: Implement xen_get_free_region()

To: "H. Peter Anvin" <hpa@xxxxxxxxx>
Subject: [Xen-devel] [PATCH] xen mtrr: Implement xen_get_free_region()
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Fri, 27 Feb 2009 17:59:24 -0800
Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Mark McLoughlin <markmc@xxxxxxxxxx>, the arch/x86 maintainers <x86@xxxxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>
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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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