[PATCH] x86/HVM: avoid memory_type_changed() invocations when possible

[PATCH] x86/HVM: avoid memory_type_changed() invocations when possible

[Jan Beulich]

They're expensive, and nothing changes if MTRRs are disabled and any of
the ranges gets changed, or if fixed range MTRRs are disabled and any of
them gets changed.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/hvm/mtrr.c
+++ b/xen/arch/x86/hvm/mtrr.c
@@ -472,7 +472,9 @@ bool_t mtrr_fix_range_msr_set(struct dom
                 return 0;
 
         fixed_range_base[row] = msr_content;
-        memory_type_changed(d);
+
+        if ( m->enabled && m->fixed_enabled )
+            memory_type_changed(d);
     }
 
     return 1;
@@ -515,7 +517,8 @@ bool_t mtrr_var_range_msr_set(
 
     m->overlapped = is_var_mtrr_overlapped(m);
 
-    memory_type_changed(d);
+    if ( m->enabled )
+        memory_type_changed(d);
 
     return 1;
 }




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Re: [PATCH] x86/HVM: avoid memory_type_changed() invocations when possible

[Andrew Cooper]

On 16/07/18 17:45, Jan Beulich wrote:
> They're expensive, and nothing changes if MTRRs are disabled and any of
> the ranges gets changed, or if fixed range MTRRs are disabled and any of
> them gets changed.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

There is still far more room improve here, but this is a start.

Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

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Re: [PATCH] x86/HVM: avoid memory_type_changed() invocations when possible

[Roger Pau Monné]

On Mon, Jul 16, 2018 at 10:45:41AM -0600, Jan Beulich wrote:
> They're expensive, and nothing changes if MTRRs are disabled and any of
> the ranges gets changed, or if fixed range MTRRs are disabled and any of
> them gets changed.
> 
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.

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