linux-kernel - Re: Question Regarding ERMS memcpy

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Message-ID: <20170306133327.usksddtpum7fftqs@pd.tnic>
Date:   Mon, 6 Mar 2017 14:33:28 +0100
From:   Borislav Petkov <bp@...e.de>
To:     Logan Gunthorpe <logang@...tatee.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Peter Anvin <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Tony Luck <tony.luck@...el.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Question Regarding ERMS memcpy

On Mon, Mar 06, 2017 at 12:01:10AM -0700, Logan Gunthorpe wrote:
> Well honestly my issue was solved by fixing my kernel config. I have no
> idea why I had optimize for size in there in the first place.

I still think that we should address the iomem memcpy Linus mentioned.
So how about this partial revert. I've made 32-bit use the same special
__memcpy() version.

Hmmm?

---
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 7afb0e2f07f4..9e378a10796d 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -201,6 +201,7 @@ extern void set_iounmap_nonlazy(void);
 #ifdef __KERNEL__
 
 #include <asm-generic/iomap.h>
+#include <asm/string.h>
 
 /*
  * Convert a virtual cached pointer to an uncached pointer
@@ -227,12 +228,13 @@ memset_io(volatile void __iomem *addr, unsigned char val, size_t count)
  * @src:		The (I/O memory) source for the data
  * @count:		The number of bytes to copy
  *
- * Copy a block of data from I/O memory.
+ * Copy a block of data from I/O memory. IO memory is different from
+ * cached memory so we use special memcpy version.
  */
 static inline void
 memcpy_fromio(void *dst, const volatile void __iomem *src, size_t count)
 {
-	memcpy(dst, (const void __force *)src, count);
+	__inline_memcpy(dst, (const void __force *)src, count);
 }
 
 /**
@@ -241,12 +243,13 @@ memcpy_fromio(void *dst, const volatile void __iomem *src, size_t count)
  * @src:		The (RAM) source for the data
  * @count:		The number of bytes to copy
  *
- * Copy a block of data to I/O memory.
+ * Copy a block of data to I/O memory. IO memory is different from
+ * cached memory so we use special memcpy version.
  */
 static inline void
 memcpy_toio(volatile void __iomem *dst, const void *src, size_t count)
 {
-	memcpy((void __force *)dst, src, count);
+	__inline_memcpy((void __force *)dst, src, count);
 }
 
 /*
diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
index 3d3e8353ee5c..556fa4a975ff 100644
--- a/arch/x86/include/asm/string_32.h
+++ b/arch/x86/include/asm/string_32.h
@@ -29,6 +29,7 @@ extern char *strchr(const char *s, int c);
 #define __HAVE_ARCH_STRLEN
 extern size_t strlen(const char *s);
 
+#define __inline_memcpy __memcpy
 static __always_inline void *__memcpy(void *to, const void *from, size_t n)
 {
 	int d0, d1, d2;

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--