Re: Prefetches in memcpy

[Carsten Langgaard <carstenl@mips.com>]

[-- Attachment #1: Type: text/plain, Size: 604 bytes --]

Here's what I think we should do for now (attached patch).

/Carsten


Dominic Sweetman wrote:

> Carsten,
>
> > I think we should get rid of the prefetches until someone comes up with a
> > version that doesn't prefetch beyond the copy destination/source area.
>
> I agree.
>
> --
> Dominic

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[-- Attachment #2: memcpy.patch --]
[-- Type: text/plain, Size: 1770 bytes --]

Index: arch/mips/lib/memcpy.S
===================================================================
RCS file: /home/cvs/linux/arch/mips/lib/memcpy.S,v
retrieving revision 1.6.2.4
diff -u -r1.6.2.4 memcpy.S
--- arch/mips/lib/memcpy.S	19 Sep 2002 14:01:24 -0000	1.6.2.4
+++ arch/mips/lib/memcpy.S	5 Dec 2002 15:06:58 -0000
@@ -21,6 +21,17 @@
 #define src a1
 #define len a2
 
+/* 
+ * There is spread a number of PREF instructions in the memcpy function, but 
+ * there is no check if we are prefetching out-side the "memcpy" areas. 
+ * This is extremely dangerous because we might prefetch out-side the physical
+ * memory area causing e.g. a bus error or something even more nasty. 
+ * It could also hit a DMA buffer region, and there by break the PCI DMA 
+ * flushing scheme.
+ * So for now, we simply get rid of the PREFs here.
+ */
+#define PREF(hint,addr)
+	
 /*
  * Spec
  *
Index: arch/mips64/lib/memcpy.S
===================================================================
RCS file: /home/cvs/linux/arch/mips64/lib/memcpy.S,v
retrieving revision 1.9.2.3
diff -u -r1.9.2.3 memcpy.S
--- arch/mips64/lib/memcpy.S	19 Sep 2002 14:01:24 -0000	1.9.2.3
+++ arch/mips64/lib/memcpy.S	5 Dec 2002 15:06:59 -0000
@@ -21,6 +21,17 @@
 #define src a1
 #define len a2
 
+/* 
+ * There is spread a number of PREF instructions in the memcpy function, but 
+ * there is no check if we are prefetching out-side the "memcpy" areas. 
+ * This is extremely dangerous because we might prefetch out-side the physical
+ * memory area causing e.g. a bus error or something even more nasty. 
+ * It could also hit a DMA buffer region, and there by break the PCI DMA 
+ * flushing scheme.
+ * So for now, we simply get rid of the PREFs here.
+ */
+#define PREF(hint,addr)
+	
 /*
  * Spec
  *