[Xen-devel] [PATCH 4/6] xen mtrr: Implement xen_get_free_region()

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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.

[ Impact: complete xen mtrr implementation ]

Signed-off-by: Mark McLoughlin <markmc@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 arch/x86/kernel/cpu/mtrr/mtrr.h |    2 ++
 arch/x86/kernel/cpu/mtrr/xen.c  |   28 +++++++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.h b/arch/x86/kernel/cpu/mtrr/mtrr.h
index 3502f6c..52bd87d 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.h
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.h
@@ -5,6 +5,8 @@
 #include <linux/types.h>
 #include <linux/stddef.h>
 
+#include <asm/mtrr.h>
+
 #define MTRRcap_MSR     0x0fe
 #define MTRRdefType_MSR 0x2ff
 
diff --git a/arch/x86/kernel/cpu/mtrr/xen.c b/arch/x86/kernel/cpu/mtrr/xen.c
index 3077bb3..f99fa15 100644
--- a/arch/x86/kernel/cpu/mtrr/xen.c
+++ b/arch/x86/kernel/cpu/mtrr/xen.c
@@ -15,11 +15,37 @@
 
 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,
-       .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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